Engineering the Future of Loudspeaker Design

DECEMBER, 1956

50¢

ENGINEERING MUSIC SOUND REPRODUCTION

The problem of building stable transistor amplifiers hinges on the stabilization of the individual stages. See page 47 for the details.

Build this concrete.block speaker enclosure which is put together like building blocks and which may be taken apart and reassembled easily in another location. See page 21.

THE FUTURE OF LOUDSPEAKER DESIGN GRAPHICAL SOLUTION OF ELECTRICAL FILTERS INCREASING SENSITIVITY OF FM TUNERS MULTIPLE TAPE COPYING

www.americanradiohistory.com SKITCH ...on his Presto Turntable

"MY CUSTOM HI -FI OUTFIT is as important to me as my Visit the Hi -Ft Sowed .Salon nearest you to verify Mr. Mercedes -Benz sports car," says Skitch Henderson, Henderson's comments. Whether you currently own a con- pianist, TV musical director and audiophile. "That's ventional "one- piece" phonograph -or custom components- we be with the difference you'll hear why I chose a PRESTO turntable to spin my records. In think you'll gratified you records through custom hi -fi components my many years working with radio and recording when play your teamed with a PRESTO turntable. Write for free brochure, studios I've never seen engineers play back records on "Skitch, on Pitch," to Dept. AX, Presto Recording Corpora- anything but a turntable -and it's usually a PRESTO tion, P.O. Box 500, Paramus, N. J. turntable. MODEL T -2 12" "Promenade" turntable "My own experience backs up the conclusion of the en- (33'h and 45) four pole motor, $49.50 MODEL T-18 12" "'Pirouette" turntable gineers: for absolutely constant turntable speed with no 031/4,45 and 78) four pole motor, annoying 'Wow' and 'Flutter,' especially at critical with Hysteresis motor (Model T-18H), ,131.00 33'%s and 45 rpm speeds, for complete elimination of MODEL T -68 16" "Pirouette" turntable motor noise and 'rumble,' I've found nothing equals a (33%, 45 and 78) four pole motor, i. with Hysteresis motor (Model T -68H), PRESTO turntable. It's heavy ... it's brilliantly machined $170.00 .... it's the only instrument on which the genuine audiophile should ever allow his records to be played." WALNUT "PANDORA" Turntable Cab- inet by Robert W. Fuldner, $42.60

Hear the difference when you play your records on "PIES/715P TURNTi4BLES

11NnNOlICS COIVONAEION AFFILIATE

www.americanradiohistory.com THE BRITISH INDUSTRIES

again .. that 414Firresistible impulse!

1 There are, apparently, some impulses which are positively irresistible.

I One of these is for uninformed writers to always try to be funny or sarcastic when they write about high fidelity. The case in point this mnth is the New Yorker's "Talk of the Town" and its ( ?) his ( ?) coverage of the recent New York High

I Fidelity Show.

1 The "Talk of the Town" finds it pos-

t Bible to be pleasantly sympathetic to a

1 group of citizens who inexplicably take a pleasure from wandering about New York City gaping at the cornices on old buildings. It can be warmly tolerant of match book collectors who, when they w meet, apparently wear shirts imprinted m like match book covers! These people o are OK in the New Yorker's book, but when a high fidelity show is visited, an attempt just has to be made to make all the visitors appear to be just plain "nuts." . Passing comments overheard in the cor- n ridors are quoted out of context, the Of noise is exaggerated and the fact that o completely different types of music are being played in different exhibit rooms has to be made to sound balmy. u The "Talk of the Town" comments that many exhibitors had their "little white 1 rooms" strung with velvet rope, "like a funeral parlor." Of course, funeral parlors aren't amusing per se, but the associa- tion strikes "Talk of the Town" as something comic to point out to its readers. Now, we don't know how many sorts of velvet ropes there are, but we are sure that the ones used at the High Fidelity Show were not only similar to those used in funeral parlors, but equally similar to those used at the Pump Room, the 21 Club and in the lobby of the theatre where "My Fair Lady" is now being shown. Why reach from left field to make it sound droll, and make a pass at the people who stand behind it or in front of it?

We wish that we could truly understand the compulsion which makes it necessary to treat the desire for quality in musical reproduction as if it were a sort of harm- less lunacy. Frankly, we just don't fathom it. We took a careful look at this column, and were made to wonder whether this writer, with his "unedu- cated tympanum," seriously meant to comment on high fidelity components or

(over) www.americanradiohistory.com (continued)

on the high fidelity show. Fully half of the space was given to a discussion of one manufacturer's television exhibit and another's short wave packaged unit, neither of which, of course, are high fidelity equipment anyhow. More than two- thirds of the article covered intro- ductions, the lyrics of a few records being played and the above irrelevancies.

We, of course, have no way of knowing what sort of equipment is used by the Editor of "Talk of the Town" when he listens to recorded music, if indeed he does at all; but even if it is not worthy of the title "high fidelity equipment," it is probably infinitely better than the sort of thing he was listening to some years ago, and this upgrading of the entire field is demonstrably due to the efforts of the same high fidelity enthusiasts he pans in his column.

As is well known, there are an awful lot of sincere and honorable men in our industry who have honestly striven to produce better and better equipment, trying to bring a greater degree of listening pleasure to devotees of recorded music. To go out of one's way to make these people appear comic is certainly out of line ... especially at this time, when so many of the audience of the New Yorker have become seriously interested in the subject of high fidelity.

We are, of course, not suggesting that high fidelity enthusiasts ought to cancel their subscriptions to the New Yorker. We certainly do not intend to cancel ours. And despite the rather shoddy treatment we think our industry has been accorded, we still find "Talk of the Town" well

worth anybody's reading any week .. . in fact, we heartily recommend it. On the other hand, those of us who take our industry (one could say our "art") seriously, would not be wrong to take the old pen in hand and drop a note when it appears that any publication is strain- ing violently in order to introduce a comic or sarcastic aspect to what is a worthwhile and progressive industry.

We wouldn't attempt to match wits with "Talk of the Town." As Joe E. Lewis says, we might be entering the fray half prepared! But we will match sincerity of purpose any old day ... and we'll bet that our airedale can lick his airedale!

Leonard Car'

Leonard Carduner is President of British Industries Corporation, Port Washington, New York. BIC is an American company which offers you the finest of audio equipment . . fully guaranteed, with service and spare parts available throughout the country.

The B.I.C. Group consists of the following products: Garrard Record Players Leak Amplifiers Wharfedale Loudspeakers R -J Enclosures River Edge Cabinets Gentiles Tubes Ersin Multicore Solders

www.americanradiohistory.com DECEMBER, 1956 VOL. 40. No. 12 a complete music center Sneeessor to RADIO. Est. 1917. amplifiers, tuners, speakers, cabinets: 5hgnizezad HIGH FIDELITY AU D i 0 THE ULTIMATE* EYCINEERINC MUSIC SOUND REPRODUCTION

C. G. McProud, Editor and Publisher Henry A. Schober, Busirr.. Manager llarrie K. Richardson, Associate Editor Joan Dioguardi, Assistant Editor .lanet M. Durgin, Production Manager Edgar E. Newnan, Circulation Director

Sanford L. Cahn, Advertising Director MEMBER Special Representalive- tE0 II. Thorpe Covington, !6 East Pearson Street, Chicago II, Ill. DEL 7 -0506 Mid Wes/ Rrpre.ventative- uE Sanford It. Cowan, 67 West 14th New York 36, N. F. Il'r.st Coast Representalires- James C. Galloway and J. 11'. Harbison, 633.1 Wilshire Boulerartl, Los Angeles 48. Calif. the all new SI000II 'ON 'l'I:N'l'S 20 watt amplifier

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Record Revue ('teak!' . -Edward Tatnall 60 Frequency Response at 20w: 20-30,000 cps ± 1 db. New Products 63 Preamp Sensitivity: 3mv. Preamp hum level: 60 db below rated output. 105 watts, 6 New Literature 70 fused. tubes plus rectifier. Size: 14 x 101 x 4 in. high. Audio ETC -Eduard Tatnall Canby 7° Employment tin One year warranty Industry Notes ;nad People S5 net price from $9950 _. 11i, Annual Index ti7 Technical literature available on request. Advertising Index tis Write Dept. A -12

AUDIO (title registered U. S. Pat. Oit.) is published monthly by Radio Magazines, Inc., Henry A. Schober, President; C. O. McPrond, Secretary. Executive and Editorial Offices, 204 Front St., Mineola, N. Y. Subscription rates -U. S., Possessions, Canada and Mexico. $4.00 for one year. $7.00 for two years. all other countries. $5.00 per year. Single SkywDsord copier 50e. Printed In l'. S. A. at Lancaster, Pa. All rights reserved. Entire contents copyright 1950 by Radio Magazines, %i rcr.ONIC uaoanTODU. oac. Inc. Entered as Second Class Matter February 9, 1950 at the Post Office, Lancaster, Pa. under the Act of March 3, 1879. RADIO MAGAZINES, INC., P. O. Box 629, MINEOLA, N. Y. 2802 WEST CULLOM AVENUE, CHICAGO 18, ILLINOIS

AUDIO DECEMBER, 1956 1

www.americanradiohistory.com HAROLD LAWRENCE

Watch Your Language! LOADED with PROFIT LONG BEFORE the curtain fell on the New merely the ever popular Carmen and Ligntweight, York City Opera Company's season Bohème. miniature size, opener, Orpheus in the Underworld, an The history of opera performances in greater compliance old controversy was being warmed over in Europe represents by the same token New mechanical the minds of the audience. Offenbach's "opera for the people." Most operas are construction gives bubbling satire on Greek mythology had heard in higher output the nation's own language. Die just been provided with a brand new Eng- Götterdämmerung at the Paris Opéra be- New "throw- away" lish libretto filled with the sort of jokes comes element Le rrèpuscule des Dieus, in Milan that would be summarily rejected at a Die Zauber¡löte is turned into II Flauto Simple replacement, preliminary conference of gag writers for .1lagico, snap -in action and Berliners hear Pagliacci as a TV comedy hour. The rhyming was Der Bajazzo. In fact, only in the United Assorted stock greeted by what a Time reporter described States orders totaled for is there such a purist approach to as the "embarrassed sighs of the audi- opera translation. maximum discount ence.'' "Clearamic" -The "new Until recent years, when the Metropoli- look in good listening" Example : tan Opera and other companies in the land JUNO -The air is full of your infideli- began introducing opera in English, Amer- New Turnover Type ties. icans seldom heard their native language JUPITER -Not The hell it is. on the operatic stage. This was, of course. Nor was the musical score helped by con - a concomitant effect of the nation's cul- ductor Erich Leinsdorf's un- Gallic in- tural inferiority complex which set a pre- t. rpretation. All in all, this English ver- mium on anything imported from Europe. sion of Orpheus had not merely broken Thus, foreign conductors, singers and opera through companies roamed the countryside Response ... 40- 12,000 cycles the language barrier; it had shat- perform- ing works Output ... 1 -1.2 volts tered it. Once again, the topic of opera in in strange languages for be- English had been re- opened for discussion. wildered audiences. Since Europeans them- New Single Needle Type Opponents of opera translation, how- selves seldom hesitate to translate libretti, ever, really could not base their arguments why should we As for the esthetic con- on the new Orpheus, since their adversaries siderations, the fact that Mozart welcomed would readily admit that the libretto was performances of his works in different a dismal failure. The debate will therefore European capitals and languages should have to revolve around better examples. go further in convincing the doubtful. Response ... 40-12,000 cycles But whatever specific translations are ex- Another point in favor of opera in Eng- Output ... 1 -1.2 volts amined, certain issues will invariably be lish was introduced by Paul Henry Lang raised. in the New York Herald Tribune on April Turnover type features Elaborate 10, 1955. "Every foreign language," wrote cases have been prepared on Mr. Lang, "calls for "throw- away" element both sides. Supporters entirely different offering snap -in replace- of opera in English voice production.... In generally maintain the following: Italian, there are ment of both element and no clusters of consonants, therefore an needle assembly for es- John Mason Brown's statement that Italian voice, even when raw and untutored, sentially the price of a "every opera is too long except Carmen," soars freely." vowel good replacement needle. Special elements of is shared by large numbers of music lovers qualities, consonantal structure, as well as Single needletypefeatures whose appreciation of opera depends upon simplified self -locating climatic effects on vocal development apply needle replacement. an understanding of the text. The weighty to French, German, English, and all philosophy of Hans Sachs' famous mono- tongues. Therefore, continued Lang, such Ask for the handy new logue from Die Meistersinger, the intricate Metropolitan Opera singers as Rise Stevens, "dispenser" assortment and amusing goings -on in Count Almavi- - meets almost all re- Leonard Warren, George London and placement needs. va's castle in Le Nozze di Figaro, the Roberta Peters perform under handicaps Tsar 's struggle with his conscience in Boris when they sing in Italian "because they Godounov -these and other operatic situa- are forsaking their mother tongue and all tions are lost to audiences not intimately that this implies in natural ease of voice acquainted with the libretti. Opera goers production." who insist upon all operas being sung in Literal translation of opera libretti is the original tongue are members of a snob- obviously out of the question, the advocate P ELECTRONICS bish, multi -lingual minority who, along of opera in English readily confesses. DIVISION with the trained musicians, want to keep Howard Dietz, whose English versions of ELGIN NATIONAL WATCH COMPANY the art form in the hands of a few. Con- Fledermaus and Bohème are incorporated For Cartridges: versely, opera in English would automatic- in the Metropolitan repertoire, described I 2435 N. NAOMI STREET, ally enlarge the audience and pave the way this task as being "more difficult than the BURBANK, CALIFORNIA for wider acceptance of all operas, not most difficult crossword puzzle." How- Sales representatives in principal cities. ever, since there is plenty of room for im- * W. Ninth St., New York 11, N. Y. provement in many libretti, no harm is

2 AUDIO DECEMBER, 1956

www.americanradiohistory.com 1. 4POLE SHADED "INDUCTION SURGE" MOTOR gives this changer constant speed with minimum vibra. tion. Will not cause hum even with these sensitive pickups. The rotor is dy. namically balanced!

are the 2. FULL MANUAL POSITION: Just touch the switch and tone arm is freed for manual play. Returns auto. features matically to its rest at end of record. 3. ADVANCED GARRARD PUSHER PLATFORM: After twenty years still the only device insuring positive, gentle handling of all records, any diameter, thickness or condition of center hole.

4. PERFECTED TRUE-TURRET DRIVE operates directly off motor without belts. Combined with an oversized that have "soft tread" idler wheel, it gives you unfaltering speed without wows of flutter.

made it 5. INTERCHANGEABLE SPINDLES (Manual and Automatic) insert easily, remove instantly. Note that the Garrard one -piece spindle has no moving parts to nick or enlarge center holes.

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7. HEAVY STEEL PRECISION TURN. TABLE with genuine rubber traction mat. A full inch highl Eliminates magnetic hum by strengthening motor shielding. Turns on silent, free -wheeling ball -bearing mount.

B. EXCLUSIVE SENSIMATIC TRIP "two MECHANISM gives you sure opera. tion even with tone arm set at lowest tracking pressures. Automatic stop after last record.

9. INTERCHANGEABLE PLUG.IN The HEADS accommodate your personal choice of high fidelity pickups, Bt all cartridges ... magnetic, crystal or ceramic; turnover, twist or simple WORLD'S plug -in types.

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/ 'JD10 DECEMBER, 1956 3

www.americanradiohistory.com done in this particular case. So much for the proponents of opera in English.

The Argument Against The basic argument against presenting opera in English is that opera translations involve more than word meanings. A great opera is a perfect marriage of words and music. The rise and fall of the melodic line in "Voi the sapete" from The Mar- riage of Figaro blends exquisitely with the instrumental score, and with Da Ponte's Italian verses. Even the most poetic translation would sound commonplace next to the original. The flow of these words was in Mozart's mind when lie created his musical setting. IIad he been provided with a German text, something else would un-

3 NEW FEATURE - doubtedly have evolved. Of all opera com- PACKED AMPLIFIERS! posers, Mozart was especially sensitive to (Models 99C, 210E ro,u- the relationship of words to notes. plete amplifiers, 121C Since literal translations are impractical. preamplifier) - 210E Color the English libretto must of necessity con- marked Green Dot con. tain some entirely new material not found trols that make it easy for your family to operate in the original. Where there is a play ou

your hi fi system . words or a witty sequence of rhymes, smartly designed mahoga- changes are unavoidable. But the result,

ny cabinets . . years in many instances, amounts to far more ahead features that defy than a mere verbal substitution; it can obsolescence . that's affect the fundamental meaning of a scene H. H. Scott for '57, your or a role. best dollar investment. The fact that European theatres give See for yourself! opera in the native tongue does not justify 4 NEW SUPER -SENSITIVE TUNERS! the practise. Anyone who has heard Wotan (Models 33o13, 3318 AM -FM tuners; 31113, 310B FM tuners) soliloquizing in French, or Manon saving 330B For the first time AM that gives you audio response beyond 10 kc farewell to her little table in German ... FM with new wide -band circuitry that makes drift a thing of the realizes how ludicrous such productions past ... AM -FM tuners equipped for Stereophonic (binaural) operation. can become. That's H. H. Scott for '57. Hear for yourself! One of the more practical objections to opera in English is that you can't under- 2 COMPLETELY REDESIGNED stand the singers any better than when POWER AMPLIFIERS! they're performing in a foreign tongue. (Models 240, 283) Exclusive Dynamic While it is true that Mozart agreed to Power Monitor on Model 280 affords full in output on music, yet protects expensive have his operas performed different languages, his primary objective was to speakers against burnout . variable damping controls for perfect speaker match- obtain performances and not to make his ing . new exterior styling . . clean operas understood by foreign audiences. distortion -free performance typical of all Paul Henry Lang's statement on vocal H. H. Scott components. Judge for yourself ! production as related to language demands 280 ALSO SEE TIE NEW 710A TURNTABLE is undisputed. But every leading opera company with an international repertoire contains a roster of singers from many countries. Logically, all of these com- Visit your dealer or write today panies are "handicapped." for complete technical specs. In 1949 an English film company produced an excellent version of Pushkin's Queen of Spades. Apart from Anton Wal- brook, everybody in the cast delivered their if H Sc ott lines in clipped, British accents. The effect 385 Put Inc Cambridge was a little bit disconcerting. In the same Mass. way, opera in English can erase the flavor of the original. te l'fea A year ago, a man named Paul W. sp c Samuel came up with a solution for the Nafie hatJOnY°111' irreconcilable arguments for and against ddtess li c opera in English. He suggested to Rudolf ta!°8 Bing of the Metropolitan Opera House Cft S Y °ptt c°oPon41-12a that, "during the performance, there .. eatsñd would be a finned strip of an English \ translation high above the stage or right , I . below it. . . . Everybody would be able State to understand every word at all times, I regardless of language barriers. Such a filmed strip would no more detract from . the flow of the opera than do the English titles during the performance of a French Export Dept: Tedesco International Corp., 270 Park Ave., N. Y. 17 'S movie."

4 AUDIO DECEMBER, 1956

www.americanradiohistory.com There's nothing between you and the music ... not even price!

This new Sonotone Linear Standard Speaker System times its size. Note how true acoustical damping and gives you more than just "presence" -the feeling that a high flux -density design give amazingly true tran- the music is being created right in the room. It gives sients, put a new crispness into rapid passages. Note you "absence," too. Gone is all awareness of "loud- the rich basses, totally free of coloration. You hear each speaker sound "... there is nothing between you and instrument as purely as in the concert hall. And you the music. look at a meticulously detailed and finished cabinet Not of even price! Compare this system with those cost- classic modern design. Isn't this the speaker system ing several times as much, including systems many you want? $199 NET. Price slightly higher in the West.

SONOTONE CA -15 COAXIAL SPEAKER has a huge 5 -1b. Alnico V magnet, with 15,000 gauss flux density. Available separately at $96 NET. Unusual velour UNIQUE, suspension of the rigid, curvilinear cone drops resonance to 30 ELLIPTICAL cycles, keeps ex- CONE EXTREMELY HEAVY treme "lows" full, rich and natural. The TWEETER MAGNET ASSEMBLY six -inch non -metallic cone tweeter is elliptical, providing wide lateral dispersion of "highs" without tinniness or piercing effect. 25 watt output, 40 watt peak. Both the W -15 woofer and the LINEAR OUTPUT, T -64 tweeter are available individually 20 TO 17,000 CYCLES at $78 NET and $7.50 NET respectively.

Electronic Applications Division SON OTO N E CORPORATION ELMSFORD, Write for free descriptive brochure N. Y.

AUDIO DECEMBER, 1956 5

www.americanradiohistory.com The following Berlant -Concertone distributors invite you to visit their store to see the new TRIPLE PLAY RECORDERS and or get your free SS0.00 tope library or Concertone Custom Microphone for S20.000 with purchase of any Berlant- Concertone recorder.

AKRON LAFAYETTE, INDIANA PHILADELPHIA Audio Hall Lafayette Radio Almo Radio 326 W. Bowery St. 408 North Street 412 -16 North 6th St. Olson Radio Warehouse Inc. 509 Arch St. LAKEWOOD, OHIO 73 E. Mill Street Radio Electric Service Music Unlimited 709 Arch Street ALBUQUERQUE 1 3410 Detroit Ave. Hi Fi Equipment Inc. PHOENIX 816 San Mateo S. E. LAS VEGAS Audio Specialties Sound Engineering & Equipment Co. Nevada Book & Sound 333 E. Camelback Road 3011 Monte Vista, N. E. 306 E. Charleston Radio and Sound Supply Co. PITTSBURGH, PENNSYLVANIA BEVERLY HILLS 25 E. California St. Concerto Room, Inc. Crawfords of Beverly Hills 642 Grant St. 456 N. Rodeo Drive LONG BEACH, CALIFORNIA M. N. Mansfield Co. NEW YORK Dackney Electronics 937 Liberty Ave. BINCHAMPTON, 343 East Market Street Radio Parts, Inc. Morris Distributing Company Scott Radio Supply, Inc. Penn Ave. 195 Street 6339 Water 266 Alamitos Avenue BROADVIEW, ILLINOIS PORTLAND, OREGON Hi -Fi Unlimited LOS ANGELES Meier and Frank Co. 1305 Roosevelt Road Beverly Hi -Fi Sandy's Camera Stores 468 So. Robertson Blvd. 714 S. W. Washington Street BROOKLYN Bushnell Electronics RED HOOK, NEW YORK Brooklyn Hi Fidelity Sound Center 12026 Wilshire Flatbush Ave. Harter, Inc. 836 Gateway to Music 10 South Broadway BUFFALO 3089 Wilshire Blvd. L. A. Portable Recorders RIVERDALE. ILLINOIS Buffalo Audio Center Audio Arrowlite Co. Inc. 521 No. La Cienega Blvd. Distributors 14218 S. Indiana Ave. 153 Genessee Street Midway Electronics 2817 Crenshaw Blvd. RIVERSIDE, CALIFORNIA CANTON, OHIO Sound Unlimited Custom Music Burroughs Radio Inc. 6320 Commodore Sloat Drive Main 2705 Fulton Road, N. W. 3980 Street The Camera Center MADISON. WISCONSIN SACRAMENTO 331 Cleveland Avenue Hi -Fi Corner Hi -Fi Sound Supply 401 State Street 1910 - 16th Street CENTRAL CITY, NEBRASKA Sampson Electronics MIAMI ST. LOUIS, MISSOURI 102 G. Street Hi -Fi Associates Van Sickle Radio Company

3888 Biscayne Blvd. 1 113 Pine Street CHICAGO Continental Corporation MILWAUKEE SALT LAKE CITY 3239 W. North Hi Fi House, Inc. Sound by Craftsmen Electronic Expediters, Inc. 2630 N. Downer Street 358 South 3rd East 2909 W. Devon Avenue Photoart Visual Service SAN DIEGO Hi -Fi Inc. 840 No. Plankinton Ave. Breier Sound 10309 South Western Ave. Walk Sales 3781 Fifth Street Newark Electric Company 3131 W. North Avenue Recording Center 223 West Madison Ave. MINNEAPOLIS 1342 - 5th Avenue Voice G Vision Wright's House of Hi -Fi 53 E. Walton Place Electronic Industries, Inc. 2451 Hennepin Avenue 5140 El Cajon Blvd. CINCINNATI Paul Schmitt Music Inc. Company SAN FRANCISCO Customcrafters Audio 68 South Tenth Street San Francisco Radio & Supply Co. 2259 Gilbert Avenue 1280 Market Street Steinberg's Inc. NEWARK -84 633 Walnut Street Hudson Radio & Television Corp. SAN MARINO, CALIFORNIA 35 William Street E. O. Bulkley Co. CLEVELAND Mission St. Co. Radio Wire Television Co. 2533 Audio Craft 24 Central Ave. 2915 Prospect Ave. SAN PEDRO National Manufacturing Co. NEW YORK Bower's Music 1000 Hamilton Ave. Aircx Radio Corporation 810 So. Gaffey The Progress Radio Supply Co. 64 Cortlandt St. SANTA BARBARA 413 -415 Huron Rd. Asco Sound Corp. Pacific Audio Sound COLUMBUS 1 15 West 45th Street 2919 De La Vina Street Shaf fer Music Company Third Floor 849 North High Street Audio Unlimited, Inc. SEATTLE 119 East 59th Street Seattle Radio Supply Inc. DAYTON Goody Audio Center, Inc. 2117 - 2nd Avenue Custom Electronics, Inc. 235 W. 49th St. Tal l's 1000 South Main St. 250 W. 49th St. 1415 Third Ave. DENVER Grand Central Radio STOCKTON, CALIFORNIA Electric Accessories 124 East 44th Street Quality Sound Service Stout at 20th Street Heins & Bolet 1217 North Wilson Way 65 Cortlandt Street DETROIT Hudson Radio & Television Corp. TOLEDO Naco Distributing Co. Jamiesons High Fidelity 48 W. 48th St. Avenue 9730 Burnette 212 Fulton St. 840 W. Central K.L.A. Laboratories, Inc. Torrence Radio, Inc. Leonard Radio Co. 1314 Madison Avenue 7375 Woodward Ave. 69 Cortland? St. Lobby -Hobby, Inc. Liberty Music Shops TOPEKA, KANSAS 17300 Woodward Ave. 450 Madison Ave. Plaza Television EAST CHICAGO, INDIANA Peerless Camera Stores 140 S. Huntoon J. N. E. Television 138 East 44th Street TUCKAHOE, NEW YORK 2013 Broadway Radio Wire Television, Inc. Boynton Studio 100 Sixth Avenue 10 Pennsylvania Avenue HEMPSTEAD, LONG ISLAND Recording Wire b Tape Co. Island Audio G Hi Fi Center, Inc. TUCSON 163 East 87 Street Inc. 441 Fulton Avenue Sun Radio & Electronics Co. Inc. Art Electronic Supply Co., 145 South Park Ave. Newmark & Lewis 50 W. 20th Street 43 Main Street Terminal Radio Corporation VAN NUYS CALIFORNIA 85 Cortlandt Street Valley Electronic Supply Co. HOLLYWOOD. 17647 Sherman Way Hollywood Electronics ONTARIO. CALIFORNIA 7460 Melrose Ave. WASHINGTON, D. C. Magnetic Recorders Rudi Pock - The Original Hi Fi Shop Electronic Wholesalers 7120 Melrose Ave. 604 N. Euclid 2345 Sherman Avenue, N. W. Pacific Hi Fi PASADENA Kitt Music Company 1320 Cahuenga Blvd. Audio Associates 1360 G. Street N. W. HOUSTON 689 So. Fair Oaks Sun Parts Distributors, Ltd. Audio Center Inc. Dow Radio 520 - 10th Street N. W. 1633 Westheimer 1759 E. Colorado YONKERS Busacker Electronic Equipment Co., Inc. High- Fidelity House Westlab 1216 West Clay 536 So. Fair Oaks 2475 Central Park Ave.

6 AUDIO DECEMBER, 1956

www.americanradiohistory.com Now! ONE Berlant - Concertone Recorder does the work of THREE 114,,t7.

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AUDIO DECEMBER, 1956 7

www.americanradiohistory.com LETTERS designed specifically for Transformer Query tance by using more steel and less turns, your high -frequency end will be better. SIR: H.BUSCHMAN, Dir. of Engrg., the 6550 tube I have had some trouble agreeing with Transformers, Inc., part of the viewpoint of Mr. Crowhuret in 200 Stage Road, his article "Audio Transformer Design" Vestal, N. Y. in the September issue. Rather than attempt a piecemeal attack, I submit herein Mr. Crowhurst's Reply my viewpoint of the subject. Because your article was so informative, the only points Sin: I shall cover will be those few with which I disagree. After reading Mr. Buschman's letter carefully. An audio transformer can usually be de- it seems we do not disagree on signed by solving only the any vital points in transformer design. low- and high - Under frequency ends. Let's start at the low end the heading "Frequency Re- (1 do). sponse" in my article, I gave substanti- The first decision to be made is the type ally the same analysis of the factors af- of steel. Characteristics to be desired are: fecting low- frequency performance that high permeability and high saturation Mr. Buschman gives in his letter. There is a point, however, level. High permeability (for a given size that I would like to take and design) determines the low- frequency this opportunity of adding: in both our response (only). The high saturation level statements, we speak of saturation level as determines determining the low- frequency power; the power rating at this low - while this is frequency end. This saturation level de- basically true, it should be termines the power rating in two ways: the qualified. first is by reducing the low- frequency re- In many modern designs, saturation sponse by lowering the steel's permeability level is not immediately responsible for at these high flux densities; overload effect or distortion at the low -fre- the second is quency by causing a change in permeability, which end. The abrupt rise in reactive causes distortion. This may magnetizing current that occurs with the seem like sim- onset of plification, but it is not in error. The one saturation does not always pro- best steel is Grain -Oriented Silicon. duce a measurable distortion component. The second choice to be made is between The distortion measured under test con- grain- oriented silicon laminations ditions often does not occur until the re- or grain - active oriented silicon "C" cores. Lame are current caused by saturation is large cheaper (much) and more flexible. enough to start distortion due to tube char - "C" acterislie overload. This cores are easier to laminate (negligibly so can be an impor- if you are trying to use this to compensate tant factor in modern output -transformer design, and is one for its high material cost) and about 20 to that further stresses the 30 percent better electrically. Other vari- importance of the liaison I suggested at ables may modify these characteristics, but the end of my article. the price of "C" cores is so much higher Mr. Buschman 's quantitative assess- than lams that unless the Hi -Fi goes into ments are based on a different comparison 3 new TRIAD rocket equipment the use of 30 per cent from mine. I was comparing grain -oriented more of the cheaper laminations is defin- strip -wound C -cores with high -grade, non - HI- FIDELITY itely called for. However, this discussion is oriented silicon alloy laminations. Here I between grain -oriented steels, and not beam afraid Mr. Buschman's use of the word tween grain -oriented "C" cores and lami- "cheap" is somewhat relative. A high - output nates of poorer grades of steels. Grain- grade non -oriented alloy is much more oriented "C" cores are a better choice costly than the really cheap materials, al- TRANSFORMERS than cheap steel laminations, as so much though it is much cheaper than C -core ma- more steel and turns of wire have to be terials. The grain -oriented laminations, used on which are relatively much newer than the cheaper lams that the high - frequency response is sacrificed. The an- either of the materials I mentioned, take HSM -192 list price $75.00. swer to our second choice is up a position approximately midway be- P.P. 6550 tubes to V.C. Pri. Impedance the best grade of grain -oriented steel laminations avail- tween the two materials I compared. They 4000 ohms C.T. (split pri.) Sec. also introduce a third possibility into the 16.8.4 ohms. Frequency response able. 65 Max. The low- frequency design is now "variable relative merit" discussion. I 7-50,000. Watts Williamson type a mat- cannot agree circuit. Proper taps on primary for ter of enough turns and steel to have the to any such sweeping state- required ment as Mr. Buschman makes. In many ap- screen operation. impedance, flux density, and wire - current density. Gaps should be kept to a plications his conclusions are correct, but HSM -193 list price $75.00. minimum; however, each application must be considered on its P.P. 6550 tubes to line. Pri. Impedance this is a function of the amplifier design, since gaps are a func- own requirements, and economic compari- 4000 C.T. (split pri.) Sec. 500-250-125. sons made. The conclusions reached will Frequency response 7- 50,000. tion of the unbalanced d.c. in the primary not always agree with Mr. Buschman's. 65 Watts Max. Proper taps on primary of the transformer. The more the d.c., the for screen operation. larger the gap. The larger the gap, the His letter next mentions the amplifier larger the transformer has to be to com- designer's problem. In pre -feedback days, S -152A list price $44.60. pensate for the lower the principal low -frequency factor was pos- P.P. to V.C. Prl. Impedance inductance caused by 6550 tubes the gap. This is the amplifier designer's sible out -of- balance d.c. But with a modern 4000 ohms C.T. Sec. 4.846 ohms. feedback amplifier, the stability of the Output 65 Watts. Williamson problem, as he has to pay for the larger type circuit. Proper taps on primary transformer caused by his unbalanced d.c. whole amplifier is dependent on the choice for screen operation. specifications. of critical rolloff parameters. In some de- As far as the high- frequency end is con- signs it may be necessary to exercise close cerned, my control of primary inductance-another Write for Catalog 111-58. only contribution to your rather complete analysis of the problem would be possible reason for requiring a gap. as follows: the high- frequency dropoff is In his last paragraph Mr. Buschman ex- due to only two things- leakage induc- presses a common fallacy: keeping other tance and winding capacitance. There is things constant, increase in turns raises only one variable that affects both factors leakage inductance but reduces capacitance. in the same direction- turns. I don't See Fig. 11 in the July issue of AUDIO stress anything as much as this point: (page 18) to confirm this. I believe this Swap steel for turns. Everything else be- fallacy arises from a different application. 4055 Redwood Ave.. Venice, Calif. ing equal, if you can get the same induc- (Continued on page 12)

8 AUDIO DECEMBER, 1956

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1102 DRIVER AND $11 HORN Power: 30 watts Range: 800.22,000 cycles Impedance: 16 ohms Distribution: Hor., 90` vert., 40` Dimensions: 8.5/8" H; 18-3/8- W; t6' D Price: 802C- 857.00, 8116 -$27.00 NJND NETWORK Impedance: 16 ohms HF attenuation: 0 -1 db steps Crossover: 800 cycles Dimensions: 8-1/2"H; 5-1/2- W; 3 -1 /2" D Price: $42.00 Ns SPEAKER Power: 30 watts Impedance: 16 ohms Range: 30 -1600 cycles Mag. Weight: 2.4 lbs. V.C. Diam.: 3" Cone Res.: 45 cycles Dimensions: Diam., 15. 5/16 "; Depth, 7' Price: $60.00 1NM MGR FREQUENCY SPEAKER Power: 20 watts Impedance: 8 ohms Range: 3000-22,000 cycles Dis- tribution: Hor., 90 vert., 40 Dimensions: 2.5/8" H; 2-7/8' W; 3' D Price: $36.00 N -1eNA NETWORK Impedance: 8 ohms HF atténuation: 2 -2 db steps Crossover: 3000 cycles Dimensions: 3.1 /8' H; 2/5 -8' Square Price: $18.00

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10 AUDIO DECEMBER, 1956

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340A POWER AMPLIFIER An audio engineer's dream, the 340A uses premium power tubes of 100 watt capacity rated at a conservative 35 watts in a simple class A -1 circuit for long -lived performance stability. Frequency response: within 1 db, 5 c.p.s. to 100,000 c.p.s. Price $159. me CONTROL PREAMPLIFIER Designed specifically for the home music system. With the door shut it will blend perfectly with home furnishings, open there are controls to satisfy the most particular. 5 inputs 25 crossover selections maximum flexibility. Price, less cabinet, $135. Blond or mahogany cabinet SIS. 73501 MELODIST AMPLIFIER A 10 watt amplifier and control preamplifier in one compact furniture unit for smaller systems, apartments and dormitories. There is a choice of 4 recording curves, facilities for microphone, and 2 inputs for tape or radio tuner. 20- 22,000 cycles loudness, level and tone controls price, less cabinet, $114. Blond or mahogany hardwood cabinet $15. - 01C MELODIST REPRODUCER For inexpensive high fidelity with the utmost simplicity. Contains a world-renowned Collaro three -speed record changer, a G.E. variable reluctance cartridge with separate sapphire needles for 78 and 33 1x3 or 45 rpm records, and the superb quality of the Altec 3398 Melodist amplifier and control preamplifier. Price, blond or mahogany, $237.

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AUDIO DECEMBER, 1956 11

www.americanradiohistory.com w101.04st w..e/4 oíw LETTERS (from page 6') In input transformers, for example, increasing secondary turns increases referred The amazing new Ferrograph "66" Series is the answer to the impedance by Tr. At the same time it re- demand of discriminating music- lovers and audiophiles who duces actual capacitance by TI /s. But since seek professional results from an instrument that can easily be this actual capacitance shunts a much housed in an existing piece of furniture, or which can form higher impedance, its effect is increased by Tt /t. But this argument does not apply in part of a custom Hi -Fi installation. all cases- certainly not where all impedances are laid down in the design specifica- This unique design includes a self- contained amplification tion. system, so that - without sacrificing even one of the many The last point Mr. Buschman stresses is outstanding features of the Ferrograph - sound can be fed insufficiently specific: if you "swap turns directly into your own speaker. Or, the playback portion of the for steel," what is the "everything else" built -in amplifier may be bypassed, and sound can be fed that stays equal -wire guage, lamination stack, window shape or size? At least one through your own high fidelity system. The Ferrograph "66" of these must change in making the "ex- will easily fit into a desk, a console, a bookcase, or any piece change." How it changes will affect the of contemporary or period furniture. All that is necessary is to accuracy of Mr. Buschman's statement, which, as a cut out an opening 156" x 161/2 "; if a drawer is used, it should generalization, is mostly true. Two more points Mr. Buschman appar- e drawers may be at least 10" deep, or a pair of shallower ently considers unimportant -I presume he converted for this purpose. delegates them as problems to the amplifier designer -but I think they also point up Most attractively finished in golden bronze with ivory knobs the need for liaison: and acessories, the entire ensemble will readily harmonize with (1) Efficiency : He says a transformer the most decorous or luxurious surroundings. can usually be designed by solving only the low- and high- frequency ends. I admit that the difference between 80 and 90 per cent efficiency is only 0.5 db, and as such should not he important. However, it is also the difference, when a pair of tubes will only deliver 55 watts undistorted with a certain B+ supply, etc., between 45 watts output and 50 watts output, which can be very important to a designer in these days when watts are to amplifiers what horse power is to automobiles! (2) High Frequency Parameters: In pre - feedback days, I would agree with Mr. Buschman's statement that high -frequency dropoff is due to only two things, leakage inductance and winding capacitance. But in these days of feedback amplifiers, the response with the feedback loop closed is more important than that without feed - hack, so much closer attention to the relative valises of these parameters is necessary. In conclusion, I would like to thank Mr. Buschman for writing, and giving me the Model 66N (3eí. & 7% ips) opportunity to insert these additional $399.50 audiophile net points. NORMAN H. CROWHURST, Model 66 (7% & 15 ips) Audio Consultant, $425.00 audiophile net 150-47 14th Road, Whitestone 57, N. Y. Other Ferrograph Professional Models Loudspeakers 4111,..sa 41" . SIR: In his article "A Semicircular Expo- wEll I nential Horn" in the October issue, Dr. Cares referres to my "Concrete Monster" (Aoolo, July, 1954) and asks the question, "But how about phase agreements between, say, a 22 -foot woofer -to -ear path and a 10 -foot tweeter -to -ear path of treble sound for a listener facing the system from a living -room chair?" In my case, the bass and treble speaker horn mouths (both are exponential -horn PORTABLE MODELS WEARITE TAPE DECKS loaded) are separated left and right by about 10 feet, and are about 28 feet Model SAIN, 3 % -7', ips. built -in speaker $379.50 ips; "A" 2 heads . . $195.00; from Model 3A/NH,7'fj -15 ips, built -in speaker $425.00 "B ", S heads ... $225.00; "C ", for the listening area. Phasing is of no more simultaneous dual track operation... $250.00. importance than it would he to phase the individual instruments of an orchestra. If your local dealer cannot supply you-orders accepted by mail - Phasing of speakers is not essential unless 10 (lay money hack guarantee. they are close together, and then it makes little difference except at or near the cross- ERCONA CORPORATION (Electronic Division) over frequency. 551 Fifth Ave., Dept. 37. New York 17, N. Y. JAMES FERGUSON, 11900 Westminster Road, Toronto IS. Place, In Canada, write Astral Electric Company Limited, bí Danforth Los Angeles 66, California.

12 Allnln DECEMBER 1954

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AUDIO DECEMBER, 1956 13

www.americanradiohistory.com EDITOR'S REPORT

FONO FALLACIES

FIRST AND FOREMOST DI the year's fono fallacies is or two per cent. So there is always the possibility that the idea that because a phonograph is labeled the record itself could be off by as much as 3 per cent, "Iii -Fi" on the front or called so in the advertis- shall we say. ing is no reason to assume that it actually is high We have mentioned before that an induction motor fidelity. And before anyone gets the idea that we are does not run at the same speed when hot as it does referring to audio components, let it be made clear at when cold -the variation being about one per cent, the beginning that no such implication is intended, since the "cold" speed is likely to be about 1725 rpm nor should it be inferred by anyone. But as the pioneer while when hot the typical four -pole motor runs at in high fidelity -and as a magazine which has con- about 1740. The speed of the playback turntable de- sistently believed that standards should be kept high pends on the load placed on it- bearing friction, stylus -Ammo often cringes, figuratively, at some of the drag, or what not -and, except in the case of the most liberties taken with the tern) "hi -fi." It should only expensive professional machines which employ syn- be necessary for anyone who had ever in his life heard chronous motors and which are gear driven through a live orchestra or soloist to listen to some of the mer- vibration dampers and flutter -reducing couplings, the chandise labeled hi -fi to make sure for himself. As turntable speed depends on the tension of the idlers mentioned once before several years ago, it is regret- to some extent. table that high quality equipment is rarely offered in However, a variation of two per cent froiii the exact the same showrooms as the shoddy so- called hi -fi stuff speed through the entire system is certainly not likely because the listener does not have much opportunity to be detectable by anyone but the well trained to compare the two side by side. And with that tirade musician by those relatively few people who have go -or off our editorial mind for the month, we to more absolute pitch. The difference between C and Ct#, for specific points which might justly be called "fono example, is almost six per cent, so the difference is fallacies." about one -third of a semi -tone. In other words, the One of the more common fallacies in the minds of whole subject becomes pretty trivial when the figures newcomers is that the speed of a phonograph turn- are compared. (For those who must have the exact table must be exactly 33% rpm. Questions often come speed, however, there are several turntables and in from readers regarding some turntable or changer changers had which have a vernier adjustment, even that been timed by said reader, either by observ- though we do not think they are an absolute necessity a stroboscope ing disc or by actually counting the for anyone who does not intend to play a musical revolutions over a period of, say 10 minutes. Upon instrument along with his records.) inquiring further, we are told that the measurements were made without actually playing a record. Con- And, just to enter the season of joy and happiness sequently, our advice is that the test be repeated while with no "beefs" on our mind, let us discuss briefly playing a record, which will usually account for about just one more fallacy -that record wear is minimized two revolutions per minute at the LP speed. by decreasing stylus force as much as possible. To a But there are many things to consider in this matter certain extent this is true, but the stylus must make of absolute speed. First, unless the original tape re- firm contact with the groove at all times, and must cording was made on an exceptionally fine machine, not be allowed to "bounce" around in the groove. Not it is possible that the tape itself was not at exactly 15 only will the bouncing cause greater wear to the rec- ips-even a tiny variation in capstan diameter could ord and the stylus, but it will also cause an increase easily cause the tape to be as much as 2 per cent off in intermodulation distortion from the pickup itself. in the speed. The thickness of tape will make a differ- We believe that the optimum stylus force is that at ence in some machines. Then too, there is the fact that which IM distortion is at a minimum, and we think a second machine, which might be of an entirely dif- that figure is the one that should be recommended. ferent make, may be used for the dubbing to the And thus, having purged ourself of these thoughts, master disc. And the disc machine may be off by one we can- without hypocrisy- extend the usual

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14 AUDIO DECEMBER, 1956

www.americanradiohistory.com When your authorized Pickering Dealer is demon- into the air at a low velocity -instead of at a high strating the revolutionary new ISOPHASE SPEAK- velocity as In ordinary speakers. In addition, the ER, please, don't look behind it for the orchestra. ISOPHASE generates sound in phase from the entire Take our word for it -these magnificently realistic surface of its large curved diaphragm-instead of sounds are coming from the.curved diaphragm it- from a point source as in conventional cone speak- self. "Unbelievable," "extraordinary," "breathtak- ers. Thus the sound reproduced by the ISOPHASE ing," and "window -on -the- studio quality" are some closely approximates the unit -area energy of the of the comments we've heard from dealers and cus- original sound entering the microphone in the tomers alike. But don't be persuaded by mere words studio or concert hall. alone. Hear it for yourself. Unlike ordinary speakers, the ISOPHASE does not The Pickering ISOPHASE SPEAKER uses the elec- "break up" at high frequencies. And because of the trostatic principle to recreate musical sounds with inherent linearity of the push-pull electrostatic de- a degree of realism unattainable in conventional sign, harmonic and intermodulation distortion are speakers. virtually nonexistent -a tremendous advantage over conventional speakers. For further details, please The ISOPHASE reintroduces the original sound write Department

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AUDIO DECEMBER, 1956 15

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www.americanradiohistory.com Heathkit Model FM -3A High Fidelity FM Tuner Kit HEATHKIT SPEAKER SYSTEM KITS Features A.G.C., and stabilized, temperature- compensated oscillator. Ten speaker systems are a very vocal demonstration uy sensitivity for 20 DB of quieting. Covers standard FM These band from 88 to 108 mc. Ratio detector for efficient hi -fi $2695* of what can be done with high -quality speakers in en- performance. Power supply built in. Illuminated slide rule (With Cabinet) closures that are designed especially to receive them. dial. Pre- aligned coils and front end tuning unit. Shpg. Wt. 7 Lbs. Notice, too, that these two enclosures are designed to Heathkit Model BC -1 Broadband AM Tuner Kit work together, as your high -fidelity system expands. Special AM tuner circuit features broad band width, high Heathkit Model SS -1 High Fidelity sensitivity and good selectivity. Employs special detector $2695' Speaker System Kit signal Covers 550 1600 kc. RF for mintmum distortion. to (With Cabinet) Employing two Jensen speakers, and pre- aligned. Power supply is built in. Shpg. WI. 8 Lbs. IF coils the Model SS -I covers 50 to Heathkit Model WA -P2 High Fidelity Preamplifier Kit 12,000 CPS within t 5 DB. It Provides 5 inputs, each eith individual level controls. Tone controls pro- can fulfill your present needs, vide 18 DB boost and 12 DB cut at 50 CPS and 15 DB boost and 20 DB and still provide for future ex- cut at 15,000 CPS. Features four -position turnover and pansion through use of the SS- roll -off controls. Derives operating power from the main $2175 I B. Cross -over frequency is 1600 CPS and the system is rated a -port amplifier, requiring only 6.3 VAC at 1 a. and 300 VDC (With Cabinet) at 25 watts. Impedance is 16 ohms. Cabinet is ducted at 10 ma. Shpg. WI. 7 Lbs. bass -reflex type, and is most attractively styled. Kit includes all components, pre -cut $3995 Heathkit Model W -5M Advanced -Design High Fidelity Amplifier Kit and pre-drilled, for assembly. Shpg. wt. 30 Lbs. This 25 -watt unit is our finest high -fidelity amplifier. Employs KT -66 output tubes and a Peerless output transformer. Frequency response t I DB Heathkit Model SS -1B Range Extending from 5 to 160,000 CPS at one watt. Harmonic distortion Speaker System Kit less than I% at 25 watts, and IM distortion less than $5975 This range extending unit uses 1 %a at 20 watts. Hum and noise are 99 DB below 25 watts. Shpg. WI. 37 Lbs. a 15' woofer and a super - Output impedance is 4, 8 or 16 ohms. Must be heard to Express Only tweeter to cover 35 to 600 CPS be fully appreciated. and 4000 to 16,000 CPS. Used MODEL W -S: Consists of Model W -SM above plus Model Shpg. Wt. 38 Lbs. with the Model SS -1, it com- WA -P2 preamplifier. $81.50' Express only pletes the audio spectrum for combined coverage of 35 to W Dual- Chassis High Fidelity Amplifier Kit Heathkit Model -3M 16,000 CPS within f 5 DB. This 20 -watt Williamson Type amplifier employs the famous Acrosound Made of top-quality furniture - Model TO -300 "ultra linear" output transformer and uses 5881 output grade plywood. All parts are tubes. Two-chassis construction provides additional flexi- pre -cut and pre-drilled, ready bility in mounting. Frequency response is I DB from for assembly and the finish of 6 CPS to 150 kc at 1 watt. Harmonic distortion only 1% $4975 your choice. Components for watts. at 21 watts, and I M distortion only 1.3% at 20 Out- Shpg. Wt. 29 Lbs. cross -over circuit included with put impedance is 4, 8 or 16 ohms. Hum and noise are 88 Express only kit. Power ra- DB below 20 watts. ting is 35 watts. $9995 MODEL W -3: Consists of Model W -3M above plus Model Shpg. Wt. 37 Lbs. impedance is 16 Wt. 80 Lbs. WA -P2 preamplifier. $71.50' Express only ohms. Shpg.

MODEL xO -1

Heathkit Model W -4AM Single- Chassis High Fidelity Amplifier Kit 'Price includes 10°!. Fed. Excise tax where applicable. The 20 -watt Model W-4AM Williamson type amplifier combines high performance with economy. Employs special- design output transformer HOW TO ORDER: by Chicago Standard, and 5881 output tubes. Frequency

1 It's simple -just identify the kit you desire by its model response is t DB from 10 CPS to 100 kc at 1 watt. Har- monic distortion only 1.5'; , and IM distortion only 2.7' $3975 number and send your order to the address listed below. at this same level. Output impedance 4, 8 or 16 ohms. Shpg. WI. 28 Lbs. Or, if you would rather budget your purchase, send for Hum and noise 95 DB below 20 watts. details of the HEATH TIME -PAYMENT PLAN! MODEL W -4A: Consists of Model W -4AM above plus Model Shpg. Wt. 35 Lbs. WA -P2 preamplifier. $61.50' Express only Heathkit Model A -9B 20 -Watt High Fidelity Amplifier Kit Features full 20 watt output using push -pull 6L6 tubes. Built -in pre- HEATH COMPANY amplifier provides four separate inputs. Separate bass and treble tone A Subsidiary of Daystrom, /nc. controls provided, and output transformer is tapped at 4, 8, 16 and 500 ohms. Designed for home use, but also fine for public $355° BENTON HARBOR 25 MICHIGAN address work. Response is 1 DB from 20 to 20,000 % CPS. Harmonic distortion less than 1 at 3 DB below Shpg. Wt. 23 Lbs. rated output. Write for Free Catalog Heathkit Model A -7D 7 -Watt High Fidelity Amplifier Kit Qualifies for high -fidelity even though more limited in power than other Heathkit models. Frequency response is $1865* 11/2 DB from 20 to 20,000 CPS. Push -pull output, and Shpg. Wt. 10 Lbs. separate bass and treble tone controls. HEATH COMPANY A Subsidiary of Daysrrwn, Inc. BENTON MODEL A -7E: Same, except that a 12517 permits preampli- $20.35* HARBOR 25 MICHIGAN ficotion, two inputs, RIAA compensation, and extra gain. Shpg. Wt. 10 Lbs. Please send Free HEATHKIT catalog. Heathkit Model XO -1 Electronic Cross -Over Kit Separates high and low frequencies electronically, so they may be fed to separate amplifiers and separate speakers. Selectable cross -over frequencies Name are 100, 200, 400, 700, 1200, 2000, and 35,000 CPS. Separate level control for high and low frequency channels. Minimizes inter - $1895 Address modulation distortion. Attenuation is 12 DB per octave. City & Zone State Handles unlimited power. Shpg. Wt. 6 Lbs.

AUDIO DECEMBER, 1956 17

www.americanradiohistory.com THE HOW AND WHY OF THE WORLD'S PUREST SILICON

The purification of silicon by Bell Laboratories metallurgists has been richly rewarding. Their original research in this field revealed the chemical factors that control semiconductors; it was a major advance leading to Bell Laboratories' invention and development of transistors and the Bell Solar Battery. Now they have devised a simple but highly effective way to remove boron -one of the most difficult impurities to extract from silicon. During refining, a stream of hydrogen and water vapor is kept flowing past the silicon. As the water vapor passes over the liquid silicon, it seizes boron atoms, forming boron oxide. The oxide is then pulled away to condense on the wall of the refining tube which is cooled by a water stream. Result of refining: boron and other harmful impurities are reduced to less than one part in 10,000,000,000. The new silicon is being used to develop still better transistors and rectifiers for telephony. It is another example of how Bell Laboratories metallurgists help open the way to improved telephony.

BELL TELEPHONE LABORATORIES

World center of communications research and development

Metallurgist Henry C. Theuerer, M.A. in Chemistry, Columbia, watches a molten zone in a silicon rod under purification. Mr. Theuerer's most recent achievement was development of water -vapor treatment for removal of boron.

www.americanradiohistory.com The Future of Loudspeaker Design

NORMAN H. CROWHURST

A brief discussion of some of the differences and the differing requirements of moving -coil and electrostatic loudspeakers. The author suggests a possible arrangement which might lead to an entirely new configuration for the electrostatic unit.

MODERN LOUDSPEAKERS Of the dy- ate a negative reaction in the minds of and to the magnetic field produced by namic or moving-coil type have a great many people who might other- the magnet system in the air gap. In the been developed to an extremely wise accept it, and thereby delay its gen- electrostatic loudspeaker the driving high standard of performance, but it is eral acceptance instead of expediting it. force is produced by the electric poten- evident from all the literature on the This seems to have happened in the elec- tial between the moving and fixed plates subject and the work which manufac- trostatic loudspeaker to some extent. for given potential, and is inversely turers are putting into it that there is For some years now, we have had small proportional to the square of the dis- still dissatisfaction with the perform- electrostatic tweeter units. While these tance between the plates. If the space ance of even the best loudspeakers, al- have enjoyed a measure of popularity between the plates is increased this though at least one manufacturer makes with a minority of high fidelity fans, who means that either the sensitivity is de- the claim of producing a perfect loud- like to hear all the surface noise as as- creased in proportion to the square of speaker. There are certain inherent de- surance that their system is reproducing this increased spacing, or else a corre- ficiencies in the moving coil loudspeaker high frequencies, a great many more spondingly higher driving potential must which make it impossible to entirely people have come to the conclusion, on be applied to maintain the same driving eliminate the electro-mechanical defects making listening tests with this new unit, force. from its performance, certain manufac- that all it enables you to hear is the As we want to avoid getting up to the turers' claims notwithstanding. extra surface noise. This is largely be- region of millions of volts -which can This is undoubtedly the reason for the cause these earlier units were all de- be dangerous -the only reasonable solu- interest in such developments as the signed to take over at a very high fre- tion seems to be to keep down the dia- electrostatic loudspeaker and the Iono- quency, well towards the high end of the phragm spacing, which in turn automati- phone. Although little has been heard spectrum, and thereby to extend the cally involves limiting the available dia- about the Ionophone since the first an- range of the moving coil or dynamic phragm movement. nouncements concerning experiments units, which were already quite good, in- The next question we encounter is the stead of being given a definite allocation with it, it seems that it does not hold out one of distortion. Inherently the electro- much immediate hope of being an effi- amounting to part of the spectrum con- static driving principle, when used as a cient transducer, whereas electrostatic taining characteristic intelligence -and single -ended device, possesses non -linear loudspeakers are in production by quite not just "highs." More of this anon. distortion. The deflecting force applied Now the trend seems to be becoming a number of companies already. The to the diaphragm over its area is pro- more sensible and the crossover from the portional to the electric field intensity question comes : What hopes do the electrostatic units hold out for achieving dynamic to the electrostatic type unit has squared. This means that if the voltage is better results than the dynamic units come down to frequencies as low as 800 doubled, the force on the diaphragm is have achieved in the past few decades, cps. This begins to give us the chance to quadrupled. Under these conditions the during which they have enjoyed popu- hear how electrostatic loudspeakers can only way to keep distortion to a reason- larity? perform on program material instead of ably low figure is to use a very large just surface noise. polarizing potential with a much smaller The big reason put forward by the audio signal superimposed on it, so the electrostatic protagonists for preferring Movement Must be Small audio signal is always only a fraction of the new type, is that the dynamic loud- The big problem with electrostatic the polarizing potential. speaker causes problems arising from the loudspeakers that delayed their applica- Supposing a polarizing potential is fact that the diaphragm is driven at one tion to lower frequencies is the fact that, used of ten times the magnitude of the point, the voice coil, whereas it is ex- however the movement of the diaphragm peak audio potential; to choose round pected to radiate throughout its entire is controlled, to have any degree of sen- figures; suppose the polarizing potential surface. The electrostatic loudspeaker, sitivity it can only be allowed to move is 1000 volts, while the peak audio is 100 in theory at least, has the driving force through a very small amplitude. The volts in alternate directions. This means applied throughout the entire surface of dynamic type can use relatively large the potential between the fixed and mov- the radiating element, which gives it a movement, allowing comparatively small ing portions of the speaker vary from better inherent chance of eliminating diaphragms to be used for the radiation 900 to 1100 volts from one peak to the from the performance of the unit the of the lower frequencies. Restriction of other. The force between these elements mechanical properties of the diaphragm. diaphragm movement means that a pro- will vary in proportion to the square of It is sometimes unfortunate that a new portionately larger diaphragm area must these voltages, which can be given the product gets on the market before it has be used to radiate the same amount of numerical values, 81, 100 and 121, the achieved a status of development to energy at the low frequencies. mean, or quiescent, value being the 100 make it worthwhile. This can often cre- In the case of the dynamic type the figure. But the midway point between driving force on the diaphragm is pro- 81 and 121 should be 101, so under this 150-47 14th Road, Whitestone 57, N.Y. portionate to the current in the voice coil condition we would have a displacement

AUDIO DECEMBER, 1956 19

www.americanradiohistory.com avoids any of the pendulum kind of c-7 effects associated with dynamic transdu- cers where the driving force is applied A at one end, i.e. the central periphery of the cone, while the load is applied uni- formally distributed over the cone. f I %ED PLATES

MOVING Large Physical Size IAPMAGM d, d, V«, v-, What usually makes a large reproducer unit inconvenient is its physical bulk. ,,P LV-.,>z If it is large .27 but fiat, so that it can be placed against the wall, it can easily be -7Vbd',d ,LV2.02lal7 disguised as a picture or some similar AUDIO di7 piece of furnishing, hence o INPUT POLAE¢ING INDIO and does not INPUT provide the problem encountered in using a unit that requires to have a (A) p) la (D1 volume of 8 or 12 cubic feet to give successful reproduction. From the electro- acoustic angle, the Fig. 1. The development of the distortionless push -pull electrostatic loudspeaker uni : design of a loudspeaker now appears to (A) the basic arrangement with its drive unit; (B) this produces a linear driving force reduce to a matter of how large a dia- on the diaphragm, provided the diaphragm does not move; (C) when the diaphragm phragm we need, to be able to produce moves, the driving force becomes non -linear; (D) preventing the charge flow, men- the required air displacement at the tioned in the text, by means of the resistor R, eliminates, or reduces, this non - lowest frequency in linearity of driving force. the audio spectrum, using the permissible diaphragm movement that can be allowed in an electro- of one part in forty from the true mean, contain higher harmonics, due to the re- static loudspeaker. which means that, using a driving volt- ciprocal law of charge held. The driving A certain amount of attention is neces- age equal to 1 /10 of the polarizing volt- force on the plate or diaphragm will sary to the design of the assembly so as age, there will be a second harmonic dis- have third and other odd -order harmon- to avoid acoustic resonances due to the tortion of 21/2 per cent. ics added to it as a result of these cur- cavities that are bound to be trapped The obvious way to improve this situa- rents. behind the diaphragm. However, with tion is to provide a push -pull arrange- This can be prevented by isolating the the push -pull design, it is a fairly sim- ment, as shown basically at Fig. 1. This diaphragm so that it has a fixed charge ple matter, acoustically, to design a means the that second harmonic in the relative to the stationary plates of the system that is critically damped and will driving force will be balanced out. How- speaker rather than a fixed potential. have a flat response over the audio spec- ever this does not get rid of our distor- Under these conditions the force is due trum. It is certainly a very much simpler tion completely: under this condition the at all times to the difference in potential problem than the design of a dynamic harmonic component of the driving force between the outer or fixed plates and transducer to achieve the same result. is only eliminated provided the dia- hence the inherent distortion figure has However, we are left with an electrical phragm spacing remains unchanged dur- disappeared. And how are we going to problem now, that of producing correct ing the cycle, which means that it must maintain a constant charge on the mov- matching of impedance which an elec- not move, and if the diaphragm does not ing diaphragm instead of a constant po- trostatic loudspeaker presents to the move, how is it going to radiate any tential? amplifier. In the case sound? of a dynamic This is relatively simple. We apply transducer the matching is relatively As soon as the diaphragm is allowed our polarizing voltage to a high resist- simple and we have become quite used to move, the different electric potentials ance such that the value of the resistance to thinking in terms of this particular are not applied across uniform spaces is higher at the lowest frequency we want problem. at every instant. The higher potential to reproduce than the reactance repre- The principal elements to the imped- gets applied across a smaller gap than sented by the plate of the capacitor ance of the dynamic unit are : the voice - the lower one because the diaphragm has made up by the speaker unit. This en- coil resistance; the radiation resistance, moved over toward the electrode that is ables harmonic distortion to be reduced which appears to be in series with the momentarily at higher potential. The to a very low figure. voice coil resistance; and various other same thing will happen during the oppo- So now we have gotten rid of some of reactances reflected into the electrical site excursion. This results in genera- the disadvantages of the electrostatic tion of third and higher odd -order har- loudspeaker principle : its inherent dis- monics. tortion and the large polarizing poten- Fortunately, as Mr. Peter Walker tial relative to the drive potential. pointed out in recent articles in Wire- The necessity for a large diaphragm less World, there is a fairly simple way still remains but the diaphragm is all of overcoming this. When the diaphragm we have to provide as a radiating sur- moves, the capacitance between the dia- face. There are no large appendages as phragm and the fixed plate changes, in the dynamic loudspeaker nor is a large which means that to maintain the same enclosure required. The requirement of potential difference a charge will have the large diaphragm is not necessarily so to flow into the diaphragm. The current detrimental. Of course there still is a flowing in the center lead will be twice possible problem of resonance between the fundamental frequency, because the the diaphragm mass and the controlling Fig. 2. The basic impedance elements in same thing will happen with each excur- force, but in this case it is much simpler an electrostatic loudspeaker unit. This is sion from the center position, regardless to control because the driving force is not complete, but shows the principal of backward or forward polarity. It will applied over the entire surface. This elements.

20 AUDIO DECEMBER, 1956

www.americanradiohistory.com circuit due to mechanical and acoustical characteristics; and the voice coil inductance. This latter does not present a reactance comparable with the other circuit values until a frequency toward the top end of the audio range is reached. In an electrostatic loudspeaker, if the FEED FROM - AMPLIFIER diaphragm does not move, its impedance NARROW ELECTROSTATIC UNITS is virtually that of a capacitor. As soon I FORMED INTO A HORN as the diaphragm moves (which of course it must to radiate sound) the -.r impedance reflected back into the elec- ECiRI trical circuit contains a component of E Cql , WIIH DE o LINE done in mov- CAPqCIT F resistance due to the work HY FORNEp ' ES OF BY IN ing the diaphragm. This resistance is, of ELECTROSTATICp ' course, the useful part of the loud- NIiSCES speaker's impedance, although the biggest proportion of the impedance is due to the reactance as a capacitor. The simplest equivalent electrical circuit to an electrostatic loudspeaker is shown at Fig. 4. The basis for a possible future development of a more efficient electrostatic Fig. 2, consisting of a resistance, capaci- horn type unit, proposed in the text. tance, and inductance in series. The capacitance is due to the plates of mean that the effective resistance of the slats of connecting the two virtually in the loudspeaker behaving as a simple unit is almost entirely due to the energy parallel by using the output transformer capacitor, with some slight modification radiated in the form of sound. to feed the moving-coil loudspeaker because of the fact that its value varies Otherwise expressed, if we can pro- while the electrostatic loudspeaker is fed when the diaphragm is allowed to move. duce a constant voltage with varying from the primary of the same trans- The inductance and resistance are due to frequency across the resistance compo- former. the motional impedance of the dia- nent of the equivalent circuit, most of The basic circuit is shown in Fig. 3. phragm. The mass of the diaphragm and this component of voltage will appear If the electrostatic loudspeaker is well the associated air in contact with it as radiated output, and the frequency designed for the purpose, even without produces the inductance component, response will be extremely flat. The prob- any further resistance in the form of while the energy radiated in the form of lem then consists of providing a driving amplifier damping, its impedance com- sound is responsible for the resistance power that gives constant voltage with position will provide a frequency re- component. varying frequency, across the resistance sponse of reasonable band width. The component. capacitance and inductance elements of This necessitates the reorientation of its effective impedance in conjunction Efficiency our thinking. What we need to drive an with the resistance element, will provide The electrostatic loudspeaker is gener- electrostatic speaker is a constant cur- low and high rolloff at predetermined ally viewed as being an inefficient device rent source, or a very low damping fac- design points. as compared to other kinds of transduc- tor, instead of a constant voltage source But some feed circuits, intentionally ers. This is because the reactance of the which is represented in the high damp- or unintentionally, incorporate some ex- capacitor element in Fig. 2 is large coming factor usually provided for dynamic tra series inductance, which offsets some pared to the resistance. However, the types. of the series capacitance due to the elec- true meaning of the word efficiency Thus it is not very convenient to use trostatic loudspeaker itself and improves means the proportion of the energy ap- the same driving force with some kind the efficiency with which energy is trans- plied to the circuit which comes out as of crossover to effect the transition be- ferred to the resistance component, output and in this sense an electrostatic tween a dynamic type unit and an elec- representing radiated sound, over an loudspeaker is more efficient than any trostatic type unit in a two unit system. extremely narrow band of frequencies. other kind of transducer. By this we For this reason a popular practice con- This means the electrostatic loudspeaker is resonated at some very high frequency. This has been a popular method of making it very apparent that the small electrostatic tweeter is actually working -the unit intended only to handle from frequencies such as 5000 cps up, or maybe even higher than that. By re- sonating it to 10,000 or 12,000 cps an extremely high efficiency is achieved at this resonant frequency. As a result the surface noise becomes severely colored at this frequency, also any components in the program material at this frequency. But it satisfies the kind of hi -fi enthusiast who is merely looking for something that sounds very "high" and doesn't bother about the fidelity to the entire range. The larger electrostatic loudspeakers, Fig. 3. Basic method of connecting a dynamic and an electrostatic unit to the same having a considerable surface area, give amplifier output as a two -unit system. (Continued on page 71)

AUDIO DECEMBER, 1956 21

www.americanradiohistory.com Graphical Solution of Electrical Network Impedances

L. U. HAMVAS'k

Anyone who has tried to solve some of the more complicated electrical networks knows how difficult they can become unless he is able to resort to some labor- saving device such as is described here.

COMPUTATIONS INVOLVING electrical (OA and OB respectively). The intersec- networks frequently become very tion of 1íB with 45 -deg. transformation complicated and laborious. Even 3 line is C, the projection relatively simple networks can be very of which is D on the ordinate. time -consuming and result in much "trial The R, is marked on the abscissa and error" work. E. The intersection of ED is F and its projection Take, for instance, the very simple G. The resistance R4 is then marked case of three resistances in parallel. on the ordinate H. The projection L of the The formula is intersection K marks the resulting resistance so that R,R,R, 11 R R,R,R,R, R,R, +R,R, +R2R, I 1 R R,R,R, + R,R,R4 + R,R,R4 + R,R,R, which is anything but simple. Compare I the labor of computing the R with the o 10 zo Reactances can be handled similarly graphical solution shown in Fig. 3. -inductances in parallel and capaci- In many cases a graphical method can Fig. 2. When values differ widely, the tances in series. be used with considerable saving in time. scales may be changed and the transfor- The graphical methods described in this mation line is therefore no longer at an Resistance and Reactance paper are faster than slide -rule solutions angle of 45 deg. Let us now investigate the cases where in many cases but give answers of com- a resistance is combined with a reactance. parable accuracy. the diagram of Fig. 1.' We shall use the conventional connota- The methods described depend on the Mark R, = OA on the abscissa and tions throughout as follows: particular combination in question. 14.0B on the ordinate. Connect A and There are three of them. resistance R B and get the intersection C on a straight 1. Combinations of resistances, or ca- line drawn at a 45 -deg. angle. The pro- capacitive reactance pacitances or inductances only. X, = 2. Combinations of a resistance and a jection of OC on either coordinate is reactance. the resulting resistance, i.e., R. OD. inductive reactance XL = wL 3. Combinations of a capacitance and is most an inductance. It convenient to use regular impedance Z=R+jx crossection paper for the purpose. The magnitude IZI = [Rs + accuracy is considerably better than the X]+ X Parallel Resistances tolerances of the values of commercially phase angle 4.= tan-' Let us take two resistances in parallel, available resistors. If one resistance is much larger than for which combination it is known that The graphical solution a resistance the other, it may be difficult to mark of R and a capacitance C in series is well R,R, the smaller one accurately. In such cases known and may be found in textbooks. R, + one may use dissimilar units on the R, It is done by treating the combination coordinates. When the units are dis- as a complex vector The graphical solution is shown in similar, the slope of the transformation in an Argand diagram as it is shown in Fig. 5. B. D. 3, Box 96, Schenectady, N. Y. line must be changed so as to equal the ratio of the units. In Fig. 2 the vertical unit is ten times that of the horizontal. / Therefore the slope of the transformation line is ten to one. \ If more than two resistances are in parallel, one constructs the result of any R2 2 two of them and then add the third, the fourth, etc. Figure 3 illustrates the construction for three resistances in parallel, while A o R D A in Fig. 4 there are four resistances. R1

RI In Fig. 4 we marked R, on the horizontal and R, on the vertical coordinate Fig. 1. Graphical solution for two resist The proofs of the validity of the de- Fig. 3. Construction for three resistances onces in parallel. scribed methods are given in the appendix. in parallel.

22 AUDIO DECEMBER, 1956

www.americanradiohistory.com LC Combinations B Series LC combinations do not cause

H trouble. The two reactances, XL and Xc, i are added algebraically as illustrated in cD Fig. 9. If the point A falls above 0, then iR4 the impedance is inductive; if it is below, then the impedance is capacitive. If A L coincides with O, then the circuit is R G ' E A tuned and its impedance is zero at the R _. o R3 frequency involved. L ./NM R1 The solution for the case of the paral- o-- --1 QÓÓ o lel LC combination is shown in Fig. 10. Fig. 4. Construction for four resistances Mark point C on the ordinate so that in parallel. OC = XL and D on the abscissa so that Fig. 7. Construction for resistance and inductance in series occupies different OD = Xe. Draw a 45 -deg. line through quadrant from that with capacitance. the origin. Extend DC until it intersects The impedance is represented by the the 45 -deg. line either in the first, or in vector OA when the resistive component the third quadrant. Project the point of In Fig. 14 we demonstrate the dia- is OB and the capacitive reactance OD. intersection B onto the abscissa E. Then gramming procedure : The phase angle is ß and the magnitude OE is the impedance sought. 1. Mark R, on the horizontal (OA) is the length OA. If the intersection occurred in the first and Xc3 on the vertical (OD). When solving such problems we proba- quadrant, then OE is positive and the bly shall need the reactances of several 2. Draw the diagonal AD and drop a capacitances and /or inductances. While perpendicular onto it from the origin. it is no hardship to compute them on the _-.__ R OF will represent Z. O r A slide rule, it will be advantageous to 3. Add R4 to Z, by marking from keep some chart handy for the purpose. point F a horizontal line of length equiv- Such prepared charts may be found in alent to Rh. many publications. Most of them are 4. Draw the diagonal OB. This repre- either direct reading (on log -log paper) sents the Zot. or nomographs. easy reference, c For such 5. Starting at B, mark R, = BE and a nomograph is attached as Fig. 11. t s' Graphing the parallel combination of Xc2 = BG. a resistance R and a capacitance C one 6. Erect the perpendicular BH onto may proceed as illustrated in Fig. 6. the diagonal EG. This BH represents Z,. After marking the resistance on the 7. Mark R, = HK and Xoi = KL as abscissa as R = OA and the capacitive Fig. 6. Construction for resistance and shown (these two are in series). capacitance in parallel. reactance on the ordinate as X0= OB, 8. The diagonal L represents Z,. connect the two points A and B. Draw a 9. Now all impedances to be added are impedance is inductive. If B is in the line from the origin 0 perpendicular to in proper position. Therefore, the diago- third quadrant, then OE is negative and AB. The intersection is C and vector OC nal OL is their sum and is Z. is the impedance sought. The phase the impedance is capacitive. If DC is 10. Divide Zot by Zt and get the angle is ß and the magnitude is the parallel with the 45 -deg. line then there attenuation. length OC. is no intersection. In other words, the By following this procedure, the nu- When the reactance is inductive rather impedance becomes infinite. Then, of merical example given may be solved. than capacitive, the BL combination course, the circuit is tuned to the reso- The circuit is the one shown in Fig. 12. nant frequency of the particular LC should be handled almost as described in The published data are : the RC cases, one difference being combination. the R, = 51,000 ohms that the inductive reactance is taken positive. The two cases (series and paral- Series -Parallel Combinations R,+ R5= 500,000 ohms (potentiometer) lel) are illustrated in Figs. 7 and 8, re- Finally, let us demonstrate the use of spectively. the described methods in a somewhat complicated circuit. The circuit is part of the tone control in the General Electric preamplifier R Model Al -200. The circuit is shown in Fig. 12, and is redrawn in Fig. 13 for the purpose of analysis. ti We are interested in the attenuation x, of the circuit at any particular position of the point B of the potentiometer. The :Ittenuation is the ratio of the output and input voltages Eo t /E{ which equals D A to the ratio of the two impedances, R C Zo r /Zs, working into an infinite load, where Zoo is the impedance between the two points B and C, while Zt is the Fig. 8. Resistance and inductance in Fig. 5. Diagram representing resistance total impedance (between the points A parallel network, which is handled simi- and capacitance in series. and C). larly to that of Fig. 6.

AUDIO DECEMBER, 1956 23

www.americanradiohistory.com and AO x BO R,R, OD= _ - AO +BO X C L which is known to be the total resistance xL 0--IF-/125ö\--0 of two resistances in parallel.

To Figure 5

1 - 1 Figure 5 is the direct application of o the concept that impedances may be expressed as complex numbers. Fig. 9. Inductance and capacitance in Z = a + jb where a represents the re- series involve only vertical straight lines. sistive component, while b represents the reactive component. According to the Fig. 12. Network of tone control as nor molly drawn.

C convention, if b is inductive, its sign will be plus; if it is capacitive, its sign is minus. Thus Z always can be written Z= a +jb =R +j% Two complex quantities are equal iB if E the vectors representing them have the same length and the same direction. Thus it will be necessary and sufficient c to show that the answer reached by the graphical methods has the same phase i angle and the same magnitude as the analytical solution. This is readily seen in Fig. 5 where

// 0=- tan-1- = - tan-1

Fig. 10. Construction for capacitance and inductance in parallel. (Continued on page 82)

R4 = 5,100 ohms C,= 0.1 pf

Cs= 0.006 pf CYCLES C, = 0.06 pf 20,000 100,000 The conditions selected are:

1 0.000 R, = 160,000 ohms R, = 340,000 ohms 5.000 - 10,000 f =100 cps With these values the construction yields 27,500 ohms Zout = 1000 loo Z4 = 197,000 ohms 1000 giving 14 per cent voltage attenuation. Numerical computation (with the aid of the slide rule) resulta in 13.8 per cent. 500 100 =10

APPENDIX

To Figure 1

The two triangles OAB and DAC are 100 10 similar. Therefore 100 CD:BO =AD:AO (1) But, by construction, 5

OD =CD 50 1000 and AD =AO -OD

Thus Eq. (1) may be written 20

OD:BO= (AO - OD) :AO 10,000 .1 or ODxAO= (AO - OD) xBO Fig. 11. Nomograph useful in determining values for complex network problems.

24 AUDIO DECEMBER, 1956

www.americanradiohistory.com Concrete for Loudspeaker Enclosures

PHIL J. WALUSEK

How to build an extremely solid loudspeaker enclosure with a minimum of effort. The author indicates how simple it must be by picturing his small fry in the various stages of the construction -although he doesn't say they did it all without his help.

ERE ARE NUMEROUS references to the from one spot to another, but in the To insure mobility it was decided to high- quality sound obtainable by the sense that it can be moved from one precast the enclosure in panels to weigh IIuse of loudspeakers mounted in con- apartment to another, from one home to not more than 50 pounds each in order crete enclosures. Although the consensus another with relatively little effort. that one person could easily make, han- favors concrete it precludes the use of Concrete is an extremely flexible dle, assemble, and disassemble the en- this type of construction because of the medium. It can be moulded into any closure. The panels were mortared to- supposed lack of portability of such en- shape desired, its strength can be varied gether with plastic caulking compound closures. This, to the average individual, to suit any individual need, and its so that the enclosure has the advantage accustomed as he is to associate the word weight can be controlled to an extremely of non -vibrating mass and yet can be concrete with tremendous building proj- fine degree. Concrete lends itself to any disassembled into light weight, easily ects, sounds quite logical. number of surface treatments, can be handled units for moving to other loca- Not believing that concrete necessarily cast smooth and painted or panelled tions. one of with wood veneers or one of the many makes an enclosure immovable, Design of Enclosure generous proportions was built to prove printed plastic adhesive finishes on the the practicability of this type of con- market. The surface can be wire brushed The design of the enclosure is such struction. The enclosure was relatively to expose rough, colored, pattern, or that it insures high -quality sound re- simple to construct, requiring no spe- ordinary gravel, or can be ground away production. An endless number of types cialized skills or tools. It is extremely slightly to obtain aggregate patterns as of enclosures was studied and one that rigid to preserve the advantages of con- in terrazzo. held the greatest promise chosen. An crete construction. Last, but by far not the least, con- infinite baffle enclosing approximately The enclosure is portable, not in the crete is a relatively inexpensive material nine cubic feet and housing four fifteen - sense that it can be lifted and carried to procure and to handle, and portland inch drivers was built in a corner of a cement, its prime ingredient, is avail- twelve -by- twenty -foot living room. The i1 Shabbona Drive, Park Forest, Ill. able in any locality. drivers are mounted close together to

Fig. 1 (right). Apparently -and actually -very solid, this enclosure is built with relatively little effort. Fig. 2 (below). Diagram showing how wall- section blocks form back of enclosure.

www.americanradiohistory.com take full advantage of the "bonus factor" the concrete, mainly because it was the that accrues,' and to avoid out of phase largest, most convenient container that effects that occur in the mid -frequency did not leak, an important consideration region when drivers are separated by a when mixing concrete in the living room. distance of three diameters or more. Using the 32-ounce graduate which had Freshly mixed concrete is a material originally been purchased for compound- of high plasticity and, although it can ing the baby's formula, three quarts of be mixed stiff enough to be readily cement and six quarts of sand were shaped by hand, it is generally placed placed in the cart and thoroughly mixed in forms made to predetermined shapes with a shovel that is sold as part of a and dimensions until it hardens in order child's set of garden tools. to insure similarity in repeated patterns. Three quarts of water were then added The base for the form was 3/4 -inch ply- and the batch mixed until a consistant wood. Side forms were sawn with the color was achieved. Six quarts of light- inside edge bevelled and screwed to the weight aggregate, in this instance ex- plywood base for ease in disassembling, panded slag, were added and the entire cleaning, and re- assembling for each use. batch mixed until every particle was End pieces were fastened to the side completely coated with cement paste. pieces and to the plywood base with When using light weight aggregates it wood screws. is important to add them last since they A circular mould piece to form the have a tendency to absorb the mixing speaker opening was made by cutting water. If added earlier, inconsistant circles of Celotex and covering with batches may result. aluminum foil. This mould was fastened The concrete was mixed for a minute in place on the plywood base with wood or so longer and then shovelled into the screws. 5/16 -inch holes were drilled in form. It was pushed into all the corners, the plywood base and 3 -inch dowels were patted with a wood float, and the form pegged in to form holes in the concrete jarred by tapping with a hammer to panels through which the speaker mount- dispel as many air bubbles as possible in ing board bolts would run. The interior order to obtain a smooth finish on the surfaces of the form were brushed with surface against the forni. When it was a form oil to break the bond between the found that not enough concrete had been form and the concrete, and to facilitate made up in the first batch, smaller removing the cast panel from the form. batches were mixed up using the same proportions but in smaller amounts until Portland Cement the form was full. At this time it may be well to say a 3/4-inch reinforcing rods were forced few words about portland cement, the into place, and after thorough compact- glue that binds the sand and the gravel ing, the excess concrete was struck off together to form concrete. Portland ce- with the edge of a board very much like ment, when water is added, forms an striking the excess cap off a glass of adhesive which sets in about four hours draft beer, though the consistency was a and continues to harden while kept bit different. Since the top surface faces damp until it attains usable strength in into the enclosure, no efforts were made seven days and its maximum average to finish it other than to level it off. strength in twenty eight days. It is for The cart and the tools were immedi- this reason that contractors keep the ately washed off to prevent the cement's forms on concrete for seven days after hardening on the surfaces while the con- placement, or, if stripping forms earlier, crete in the forms was left to set. After cover the concrete with straw, burlap, or about eight hours, wet burlap cloths vapor seal, and keep it damp for the were placed on the surface of the con- proper curing time. crete and the whole covered with sheet The amount of mixing water controls plastic to prevent evaporation until the the strength of the cement paste and concrete had attained its seven -day therefore controls the strength of the strength. It was possible to speed up the concrete. The greater the amount of casting operation by carefully removing mixing water the greater the dilution, each east panel on the third day and lay- and therefore the weaker the paste. It ing it aside, covered with damp cloths is important to use only as much mixing and plastic sheets while another panel water as will give the desired strength was being cast. Two panels were cast concrete. with one speaker mounting hole per A garden cart was used for mixing panel. One panel with two speaker mounting holes was cast in the same form 'Electrical Engineer's Handbook, Fourth using two forming circles instead of one. Edition 13 -04, "Multiple pistons." Wiley, 1950. While the three panels were curing, the top was formed and cast. Top to bottom: Fig. 3. Mixing the concrete in a garden cart. Fig. 4. Brushing the Back Wall Panels interior of the form with a form oil. Fig. The room where the enclosure was to 5. Dowels make holes for speaker mount- be used was dry wall construction and ing bolts. Fig. 6. Concrete being finished it was feared that the walls would vi- with a wood float. brate, so two back walls which ordinarily

www.americanradiohistory.com would not be necessary were constructed material to minimize internal reflections. of 2 x 8 x 16 inch lightweight concrete To prevent possible damage to the driv- masonry units. Instead of laying these ers by glass dusts, a cover of muslin was up as one would lay up a wall, the units taped over the hark of eneh loudspeaker. were positioned on a plastic covered ply- Mounting the Loudspeakers wood panel in such a manner that the outside edges of the blocks came to the For the speaker mounting panels desired dimensions. The blocks were 13% -inch diameter holes were made in dampened with a fine spray of water 1S -inch squares of 3/4 -inch plywood and from a garden sprayer and a cement 3/4-inch dowel rods 18 inches long were grout consisting of one part cement, two nailed two inches apart across the open- parts sand, and one part water, thor- ings to act as a protective grille. A 1/16 - oughly mixed, was pushed down between inch cork gasket was glued to the rear the blocks to mortar them together. The of each mounting board to insure air- grout set rapidly and it was possible to tight fit. 15 -inch loudspeakers were finish off the mortar at the edges of the fastened to the rear surface of the mount- panel very well. ing boards with wood screws and the Two layers of waterproof paper were assemblies bolted to the concrete panels. placed on top of the first layer of blocks Various combinations were tried with and the second back wall blocks posi- excellent results and after numerous tioned and grouted together right on top tests, one Jensen G -610 and three Jensen of the first set. The whole was covered P -15LL loudspeakers were decided on. with wet burlap cloths and a sheet of The G -610 gives a smooth response plastic to prevent evaporation, and al- throughout the useable range, and the lowed to cure seven days. After curing, reinforcement in the bass supplied by the panels were uncovered and allowed the three P -15LL loudspeakers gives a to dry out. cleanliness in the bass that is not evident The plywood under the block wall with enclosures utilizing loudspeaker panels served as a pallet to enable the hack radiations for bass reinforcement. wall sections to be tilted up and moved It has been the opinion of the author into position without undue stress being that the use of back emanations front placed on the mortar joints. The two loudspeakers to extend the lower range waterproof sheets of paper prevented of any unit results in poor reproduction the panels from sticking to each other. of complex musical signals because it is Three -inch long 1/4 x 20 threaded roda believed impossible to accurately phase were fastened in place through the holes the back signal with the front signal. formed in the front panels by the While it is true that a reinforcement dowels, leaving one inch of rod extend- and apparent increased reproduced hand - ing beyond the face of the panel. This width into the lower bass regions is was to allow the speaker mounting indicated by test using frequency genera- boards to be attached from the front of tors, this method does not insure faith- the enclosure. ful reproduction of complex musical To prevent the panels from bonding signals which requires not only a smooth- to the floor, strips of aluminum foil were ness in volume of reproduction but also positioned where the panels would rest, in keeping all audio frequencies in their and cords of caulking compound placed proper phase relationship. thereon. The back will panels were set It is believed that this enclosure, built up on the caulking compound, positioned in the living room with the understand- in the corner, and the corner joint ing encouragement of a sympathetic caulked tight. The front panels were wife opens an entirely new field for the then placed in their bed of caulking enterprising audio fan in his quest for compound on aluminum foil, and caulked more faithful sound reproduction. The to each other. Caulking compound was lack of sympathetically vibrating struc- run around the tops of all the panels, tural panels results in a smoother com- :Ind the top was seated thereon. pletely boom free bass. And the proper- There is considerable give to the com- ties of concrete lend this medium the pound, and the panels were pushed and advantage of being the most plastic, the pulled into the best position and allowed most practicable of all materials avail- to rest until the weight of the unit able for the construction of any type, settled them somewhat. The excess foil size, or shape of enclosure imaginable. and compound were trimmed away and the whole job generally tidied up. The Top to bottom: Fig. 7. Covering panels exposed concrete surfaces were painted with wet burlap cloths ensures maximum with a latex rubber base paint. Since 7 -day strength. Fig. 8. Back panels concrete retains moisture for some time, caulked to floor with protecting layer of the enclosure was allowed to dry out aluminum foil. Fig. 9. Mounting bolts thoroughly. An electric light bulb left being fitted in holes made by the dowels. lit in the enclosure helped shorten the Fig. 10. Musician Friend places stamp of drying time considerably. approval on the enclosure. No enclosure The entire enclosure was filled with is worth its weight without the approval dd size pieces of glass wool insulating of a Musician Friend.

AUDIO DECEMBER, 1956

www.americanradiohistory.com Design for a College Music Room

MERLE FLEMING and ELLIOTT FULL

A practical arrangement for providing music to a variety of rooms and for a variety of purposes-all built under the traditional limitations of budget under which educational institutions are known to operate.

THE MUSIC ROOM in the new wing of the University of Iowa Union is rapidly becoming one of the most popular places on the campus. Within a week after the room was in regular operation, consistently from four to five times as many people were using the facilities on a regular basis. The music room is an integral part of the Student Union at Iowa. The 36 by 46 -foot room is air conditioned; the walls are of curly maple paneling and glass. The ceiling is acoustical tile and the floor is carpeted. The loudspeaker in the northeast corner is the focal point of the room. A control room houses much of the accompanying equipment.

Control Room Equipment The control room equipment used to feed the loudspeaker is as follows: Students and staff at the University of Iowa are finding that one of the best places A. Program Sources to spend several hours is the new music room of the Student Union. When the con- 1. Rek -O -Kut B -12H turntable with Fairchild diamond cartridges trol room (right window) is manned by the hostess a typical hi -fi system plays 2. Garrard RC -90 record changer with through the loudspeaker at the far corner. Otherwise the students play music from Fairchild diamond cartridges the 100 -record Seeburg Select -O -Matit shown at the left. 3. Coneertone 20/20 tape recorder 4. Stephens microphone 5. Browning AM short wave tuner an 8 -inch monitoring speaker. This may away or busy elsewhere during the B. McIntosh 30 -watt amplifier be switched between the tape recorder, normal operating time of the control C. McIntosh C -8 preamplifier the preamplifier output and the radio, room. With very careful listening, the In addition to the above equipment, thereby furnishing a means of monitor- only difference noted between the trans- the control room contains a Radio ing program sources before being played cription table and the changer is the Craftsman C -400 amplifier connected to into the music room, as shown in Fig. 1. superior ability of the Rek-O -Kut to Custom Electronic Devices, Iowa City, The record changer is to be used pri- handle the powerful bass of some organ Iowa. marily when the hostesses are called recordings and the lack of rumble even when a good deal of bas- boost is used. On most recordings, there is no perceiv- able difference in results. A hostess is on duty in the Union music room during specific hours only. No one else is allowed to operate the control-room equipment. There was thus a need for a source of music outside the control room, and with a good corner loudspeaker available, it seemed desirable to channel all music through it. A Seeburg Select- O -Matic was installed in the music room so that University students and staff may have the pleasure of the music room all the time the Union itself is open. The Seeburg drives the speaker through a Radio Craftsman C -400 amplifier and a changeover relay whenever the control room is not in use. Since non- technical people with nu- Both changer and transcription turntable play through the amplifier system in this merous other concurrent duties are in control room. The tape recorder at the right makes it possible to record student charge, all of the control room equip- activities when desirable. ment is connected to the light switch.

28 AUDIO DECEMBER, 1956

www.americanradiohistory.com Recorder -Speaker Experiment

AM RADIO Prior to the opening of the music C 400 MON room, the equipment was used to record AMP AND SPEAKER and play back to a "packed house," the SPARE TAPE RECORDER first part of a combined University chorus and orchestra concert. The recording engineer was "off speaker" and CHANGER it was therefore difficult to adjust volume properly. If this experiment were performed on a frequent basis, a volume

TURNTABLE monitoring device in the audience would 30 . ATT AMP RELAY LOUDSPKR. be desirable. Immediately following the concert, a Mc INTOSH C B short portion of the tape was played.

C 400 AMP The comments, as could be expected, AND ranged from "superb" to "I was dis- SEEBURG C-8 RECORDER OUTPUT appointed." The average remark seemed to be "It was very good, but wasn't there too much volume?" What does this Fig. 1. Block diagram of the control room equipment used in the college music room. imply to the advocates of 50 -watt amplifiers? This switch, as well as the master equip- hum conduction. This arrangement en- The issue of too much volume was ment switch and the preamplifier on-off ables each unit to be unplugged and highly debatable. The effect may have removed minimum switch, makes the large loudspeaker for servicing with a been actual or it might have been re- available to the Seeburg, as seen in of trouble. This power control box has lated to the sound from the speaker 2. mounted length Fig. a switch on a short of coming from a small radius while the cord which is in mounted the During the planning stages, many turn on concert itself came from the board control console. suggestions were made by interested source of a chorus and orchestra. University people wanting the best All speaker wiring is four -conductor equipment installed. While a wide #18 with opposite pairs tied together. This experiment took place in the variety of equipment would have given One pair is grounded and connected to main lounge of the old section of the equal or nearly equal performance, in the grounding pole of the three -prong Iowa Union. The acoustics of this room this particular situation, there was a speaker outlets. The other pair is con- are extremely bad. The ceiling is very specific reason for the purchase of nected at the speaker plug. This type low for an auditorium. It is carpeted nearly every item in the system. of wiring, with two pairs available, aside throughout and has a large quantity of Dr. Earl E. Harper, the director of from increasing effective wire size upholstered furniture, not to mention the union, decided the recorder was and improving damping characteristics, the sound absorbing qualities of 2000 essential since tape is a superior medium makes possible the installation of a people. Satisfactory mike placement in and a fine system of this type would not stereophonic audio system at a later date this situation is practically impossible. be complete without a means of using without rewiring. The music room has All this adds up to a short time con- it. It followed naturally that a micro- an extra speaker outlet, as does the large stant and lack of direct treble from the phone was also a necessity. adjacent lounge, which is 59 x 112 feet ill size. (Continued on page 81) Recording Requirements The only conceivable use for a microphone in this set -up is for recording, so the microphone is connected to the tape MASTER SWITCH recording only. Policy has input not FUSE been established for use of the recording AM RADIO LOUDSPKR. facilities. The tape machine will probably be used primarily for playing tapes of University concerts and other re- TAPE corded tapes as they become available. RECORDER The size and other attributes of the music room would make a desirable it 400 MON studio for recording small chamber or C choral groups. The University of Iowa

C B PREAMP C is unusually short of auditoriums of any AC 3 PDT RELAY size. The microphone is used for University AUDIO C 400 AMP lectures in the main lounge of the Union TURNTABLE CHANGER & AC AND and for other university functions, par- SEERURG ticularly those connected with union activities. AC FROM 30 WATT AMP AUDIO OUTPUT WALL SOCKET The individual units all connect into an a.c. and speaker control box that also houses the changeover relay and fuse. The relay is mounted on a small piece of Fig. 2. Block diagram of the a.c. supply circuits and the speaker switching for the acoustical tile to minimize chances of entire system.

AUDIO DECEMBER, 1956 29

www.americanradiohistory.com Increasing Sensitivity and Lowering Distortion In FM Tuners

JOSEPH MARSHALL

Additional gain and extra bandwidth can be added to an FM tuner by this outboard double- detection i.f. amplifier. The result is complete saturation of the limiters for quiet signals, even in fringe areas, and optimum distortion reduction for the sound.

SEVERAL PROBLEMS ARISE in the use of the limiters; therefore, on weak signals gain when the conventional design is FM tuners for high -fidelity recep- the distortion due to a narrow bandpass used. With an i.f. of 10.7 me, three i.f. tion. One is lack of sensitivity or will not be suppressed. As a matter of amplifier stages with a total gain of gain with the result that on weak signals fact, it will not be suppressed completely about 90 db represent the practical limit the limiters are not completely saturated on strong signals either. It has been for stable operation, and even this is and reception is not sufficiently noise - pointed out that when the signal has to achieved only by keeping the band-pass free. Another is distortion. One form is operate on the curved portion of the re- narrow. Therefore, highly sensitive com- the residual detector distortion even ceiver response curve, there occurs not mercial receivers (such as the REL) em- when the circuit is properly aligned and only amplitude, but phase and therefore ploy double conversion with additional the signal properly tuned in. With dis- frequency distortion. Regardless of how amplification at a frequency of about criminator and ratio type detectors this thoroughly the limiters suppress the am- 5 mc. This is both costly and critical residual distortion in the average tuner plitude distortion, they have no effect on since the addition of further tuned cir- is commonly about 1% with good align- the phase and frequency distortion which cuits, especially at a lower frequency, ment of the i.f. amplifier, and increases is then evidenced in the audio output as not only makes symmetry and linearity to higher values as the response curve serious amplitude distortion. of the response curve more difficult to is deformed by the detuning caused by This was not seriously noticeable in achieve and maintain, but also because at changes in circuit capacitance with the the early days of FM because available lower frequencies it is even more diffi- passage of time. This is not noticeable audio amplifiers generated enough dis- cult to keep the band -width large enough in the ordinary commercial FM receivers tortion of their own to mask it; but it for distortionless reception. where it is masked by higher distortion has been noted in the past few years by Just after the War, W. W. Moe of in the audio amplifier; but when a tuner those using wide -range, low- distortion General Electric suggested the use of a is used with modern high -quality ampli- systems. The need for narrowing the second intermediate frequency of about fiers whose distortion is only a fraction bandpass comes from the need for sen- 200 kc with R -C tuning of the 200 kc of 1% it can be very annoying to golden sitivity; therefore, any device which channel. This would provide additional ears. would permit an increase in gain would gain without critical tuned circuits and More serious, however, is the distor- also permit a widening of the band -pass at low cost. Moreover it would permit - tion due to improper tuning, frequency with consequent elimination of phase dis- indeed require-the use of the frequency - drift, and too narrow a bandwidth. Both tortion. counting detector which possesses the the discriminator and ratio of detector All in all, it is ironic that FM recep- best distortion characteristics of all avail- depend on the linearity of the response tion, which originally promised an ap- able FM detectors. The author con- curves of the tuned circuits for proper proximation of the ideal in radio recep- structed a receiver using this circuit. He operation, and since the tolerance is very tion, is subject to distortion which can, found it excellent except for one thing. small drift or detuning of as little as 15 and commonly does, exceed that of AM With a second i.f. of 200 kc there is an or 25 kc is sufficient to produce non- reception. In other words, as we have image point only 400 kc off resonance. linear detection. High- quality reception improved the terminal devices of the This is well within the skirts of the selec- is therefore achieved only by great care chain -amplifiers and loudspeakers -we tivity curve of a 10.7 me amplifier with in tuning and by frequent retuning to have become aware that in FM we face a 150 -250 -kc bandwidth and produced compensate for drift, even if the receiver again the same old bugaboo of high two -spot tuning on very strong signals. is equipped with automatic frequency fidelity: as we increase the total system This was not a serious problem in the control. band -width the residual noise and dis- author's case since the strongest signal Finally, a bandwidth of 150 kc at 6 db tortion limit the quality and enjoyment had a field strength less than 100 micro- down has been accepted as the compro- more and more. Fortunately, there are volts; but it did appear to limit the mise standard and is characteristic of solutions, relatively simple and inexpen- wider application of the circuit. even the highest -grade FM tuners, al- sive ones, for both problems. As is usually the case, the solution was though theory calls for a total bandwidth a very simple one but unfortunately did of 240 kc for distortionless reception. Increasing Sensitivity not suggest itself for several years, per- The idea behind the compromise is that More complete quieting, assuming the haps because the problem was not serious distortion due to the narrow bandwidth use of a two -stage limiter, requires an enough to stimulate the required concen- will be suppressed by the limiters. We increase in receiver gain to produce satu- tration. It consists of the use of absorb - have already pointed out that on weak ration of the limiters at lower signal lev- tion traps in the 10.7 -mc channel to pro- signals the gain of the average FM tuner els. Although we have had improvements vide a dip in the response curve at the is not sufficient to produce saturation of in recent models of FM tuners in this re- image frequency of 11.1 mc. At first Ozone, Tenn. spect, there is a limitation to receiver thought this appears to lead to oompli-

30 AUDIO DECEMBER, 1956

www.americanradiohistory.com PROFESSIONAL HI-FI SPEAKERS FOR PROFESSIONAL PA SYSTEMS

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DESIGNED 2 AND 3 -WAY SPEAKERS FOR PROFESSIONAL HI -FI SOUND SYSTEMS

The "chips are down" when it comes to hi -fi sound coverage in industrial, commercial and institutional systems. Many a speaker that might "get by" in a music lovers living room just won't do the job in professional installations. Here you've just got to have full efficiency, ample power handling capacity and wide -angle distribution over the frequency range. Jensen has five 2 -way coaxial and 3 -way TRIAXIAL speakers to do this job for you. All are honest multi - way units with independently- driven horn -loaded compression -driver mid and high channels with full crossover networks. They are minus frills like fancy covers and pretty nameplates but are plus on dependability features like corrosion and moisture resistant treatments. For realistic sound quality, we know of nothing the equal of these fine high performance hi -fi speakers. They work excellently in very small enclosures on ceiling or wall or suspended overhead. And of course they may be used in larger cabinetry when ultimate reproduction of "lows" is needed. Higher quality interior sound distribution systems are the trend of the future. Jensen Professional Series High Fidelity Loudspeakers insure highest quality results.

The Jensen Professional Series also includes: Lifetime Driver Units; H -535C Hypex Projector Horns; Hypex Complete Projectors; Extended Range High 2 -way Fidelity Loudspeakers; Weather Master Speakers; Transformers; Controls; coaxial Cabinets and accessories. G-615C 3-way TRIAXIAL

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AUDIO DECEMBER, 1956 31

www.americanradiohistory.com sated and nonstandard i.f. transform- This endows the receiver employing it Although the diagrammed circuit uses ers; but actually it can be achieved very with a tremendous tuning tolerance. The metal tubes, it can be converted to minia- simply with standard transformers only results are (1) that the receiver can be ture tubes. Both the 6AC7 and 6AB7 slightly modified, and results in making tuned very simply and uncritically even now have miniature equivalents. Either possible a receiver of tremendous sensi- without a tuning indicator, and (2) that the 6AH7 or the 6AU6 can be used in tivity-1 microvolt or better with full it will provide reception of very low displace of the 6AC7, while the 6AB7 can quieting -at a cost of only a few dollars tortion even without a.f.c. over a consid- be replaced by the 6BA6. The 6SA7, of more than conventional receivers. erable range of frequency drift. In fact, course, can be replaced by the 6BE6, the given a reasonably stable first oscillator, 6116 by the 6AL5. The only changes Decreasing Distortion the over -all tuning stability is compar- would be in the bias resistors-68 ohms It is very seldom that increased fidel- able to that of a broadcast -band receiver, for the 6BE6 and 100 ohms for the ity and lower distortion are obtained even without a.f.c. Although the circuit 6AU6. through the same measures which yield seems to make the receiver tune very It will be noted that link coupling is high sensitivity; but that is the case in broadly, the effective selectivity can be specified at the input. This is necessary this instance. With a terminating i.f. of made fully as good as or better than that whether or not the i.f. amplifier is ad- 200 kc the frequency -counting detector of receivers employing the more conven- jacent to the r.f. front end; in fact, it is not only possible but mandatory since tional detectors. is the secret of the satisfactory operation it would be practically impossible to ob- Finally, given the increased gain made at low cost of the whole circuit. Stand- tain the linearity at this frequency neces- possible by a second i.f. channel, we no ard i.f. transformers are used. The links sary for discriminator or for any other longer require the narrow band -width in are 3 or 4 turns of hookup wire wound type of detection dependent on the tun- the 10.7-me channel. Therefore, where at the ground end of the grid winding ing slope. The frequency counting detec- adjacent -channel selectivity is not im- and the B -plus end of the plate winding, tor has been analyzed and discussed fre- portant, the receiver can be aligned for a respectively, of the two transformers. quently in the literature and there is no bandpass of 240 kc, which will eliminate The link can be passed through a hole point in going over the ground again. A the distortion due to narrow bandwidth in the can or the base to the other trans- few points, however, are noteworthy. Since the second i.f. channel, though former. If the link has to be longer In the first place, the frequency-count- lower in frequency, is very broadly than 2 inches, it should be shielded to ing detector is completely independent of tuned, this is easy to achieve without prevent pickup of interference in the the slope of the response curve and is a critical alignment. 10.5- to 11-me range. The unused wind- very linear device per se. For this reason ing in each transformer now becomes an it is employed in precision monitors for The Practical Circuit absorption trap tuned as described sub- checking the distortion characteristics of Fig. 1 gives the schematic diagram of sequently. It is these traps, which by transmitters and generators. Residual a practical i.f. amplifier employing these eliminating or at least minimizing two- distortion can be held down to a fraction ideas, now in use in the author's FM spot tuning, make the whole circuit prac- of 1% which makes it fully comparable tuner. It consists of two stages of ampli- tical. to our best audio amplifiers. Moreover, fication in the 10.7 -me channel followed To obtain maximum gain with stabil- because it does not depend on the slope by a second converter which provides ad- ity, the 10.7 -mc channel is stabilized by of the tuning curve, it minimizes the dis- ditional amplification and converts the bypassing the plates to the screen and tortion due to detuning, whether the de- signal to 200 kc. The 200 -kc channel con- by passing from there through tuning is caused by improper centering sists of one stage of R- C- coupled ampli- to ground of the signal or by frequency drift. In fication, followed by two limiters and the the .003 -µf capacitors. This forms a fact, it will produce reproduction with frequency -counting detector. On strong bridge circuit which neutralizes the plate - very little distortion even when the re- signals, the 200 -kc amplifier becomes grid capacitance. The .01-,,f plate, grid, ceiver is detuned as much as 100 or even saturated and becomes a third limiter and cathode bypass capacitors are 125 ke off resonance-or, in other words, with the result that the receiver pos- dressed with leads about I/2 inch long. when only one set of sidebands is passed. sesses extremely high quieting ability. This provides enough inductance to form

:11

Fig. 1. The circuit schematic for the outboard i.f. amplifier. The second i.f. is at 200 kc and the detector is a frequency counter. Some old hands at audio may feel timid about tackling r.f. circuits, but there is nothing hard about it.

AUDIO DECEMBER, 1956

www.americanradiohistory.com ELECTRONICS IN BRITAIN i

The British Electronics Industry is making giant strides with new developments in a variety of fields. Mullard tubes are an important contribution to this progress. The expert choice for medium power, high fidelity equipment EL84

Principal Ratings Heater .... 6.3V, 0.76A Max. plate voltage .... 300V Max. plate dissipation 12W Max. screen voltage .... 30CV Max. screen dissipation (max. signal) 4W British high fidelity experts know Max. cathode current .... 65mA that for medium powered equipment there is no finer tube than the Base EL84. A pair of these tubes provide a power output of toW at a Small button noval 9 -pin distortion level of less than t °;, while their transconductance value of I I,30o µmhos results in exceptional sensitivity. The EL84 may also from: be used for higher powers. For example, two tubes in push -pull will Supplies available - provide outputs of up to 17W at an overall distortion of 4%. In the U.S.A. International Electronics Corporation, Dept. Al2, A single EL84 has a maximum 81 Spring Street, N. Y. 12, New York, U.S.A. plate dissipation Of 12W. It provides an output of 5 -6W for an input In signal of less than 5V r.m.s. at plate and screen voltages of 250V. Canada Rogers Majestic Electronics Limited, Dept. HO, Supplies of the EL84 for replace- 11 -19 Brentclifte Road, Toronto 17, Ontario, ment in British equipments are available from the companies listed. Canada. ELECTRONIC TUBES

Mullard ffsedattt Wie

MULLARD OVERSEAS LTD., MULLARD HOUSE, TORRINGTON PLACE, LONDON, ENGLAND

.1Jllard is the Trade Mark of Mullord Ltd., and is registered in most of the principal countries of the world.

MEV 43 AUDIO DECEMBER, 1956 33

www.americanradiohistory.com follows, like most modern high -fidelity amplifiers, has a response beyond 30,000 cps, to filter out the r.f. which might otherwise cause trouble in the audio system. The filter can be left out, in which case the 47,000 -ohm detector load resistor should be bypassed with an 0.1 -µf capacitor. The detector output is about 1 volt. Unless the amplifier is supplied by a ripple -free power supply, it is better not to have an AF amplifier on this chassis, but to obtain the needed amplification on the audio chassis. Although a tuning indicator is not necessary, it is helpful. Since proper tuning involves only peaking the signal, a simple indicator will suffice. The meter indicator diagrammed is both simple and effective, but for ordinary purposes Fig. 2. This is the author's version of the i.f. amplifier. can be replaced with a 6E5 tuning eye. Fig. 2 shows the writer's finished out- a series resonant circuit tuned to approx- presence u1 this one harmonic within board amplifier. imately the 10.7 -mc range, thus provid- the tuning range is the only disadvan- ing more effective bypassing. tage of the circuit and it is a very small Alignment And Adjustment The amount of loading of the trans- price to pay for the otherwise greatly One of the great virtues of this circuit formers if any, will be determined by the improved performance. is the simplicity of alignment and ad- transformers themselves. The Stanwyck If it is desired to add the benefits of justment. An oscilloscope is helpful, transformers used in this model provide this circuit to a presently inadequate especially in adjusting the traps and ob- a bandwidth of 150 ke with grid loading FM receiver-which can be done quite taining the best possible selectivity for only. For maximum distortion -free simply -the first and possibly the second a given bandwidth. The tuning indicator fidelity, however, the circuit provides for amplifier stages of Fig. 1 should be left alone will suffice however. A signal loading resistors in the plate circuits as out. The addition of an outboard ampli- generator will produce the best results well. This gives a bandwidth which fier of this type can be accomplished but excellent results are obtainable by equals or at least approaches the theo- without seriously disturbing the present using a station signal. The procedure is retically ideal 240 kc. receiver. The only change is to provide as follows: It will be noted that a.v.c. is applied a link on the plate winding of the i.f. First, set the second oscillator to ap- to the second converter and the second transformer following the last i.f. ampli- proximately 10.9 me. This is most easily 10.7 amplifier through a 4- megohm po- fier (but not the discriminator trans- achieved by tuning a nearly shortwave tentiometer which determines the amount former). This can be done by removing receiver to 10.9 me and turning the slug applied. Ordinarily, to get complete the shield can and winding a 3 -turn link on the oscillator coil until the receiver saturation of the limiters the amplifiers as described previously. The other wind- detects the generated signal. However, if should operate at maximum gain. How- ing is not disturbed and neither is the no shortwave receiver is available and if ever, it is possible to obtain distorted rest of the present receiver. The follow- the i.f. transformers are presumed to be reception by overloading the converter ing tubes are simply removed and the set to approximately 10.7 me, the oscil- on very strong signals. The variable - grid winding of this transformer is lator slug can be adjusted until the signal a.v.c. method of controlling gain pro- tuned as an absorption trap. The re- is detected on the meter. Final adjust- vides good control with minimum risk of ceiver can be placed in original condition ment is made later and a slight error will instability and the least possible trouble simply by removing the link, replacing make no difference. due to mishandling of controls. the tubes, and re- trimming the trans- The 10.7-me channel is now peaked in The second converter is a standard former. the usual manner. If a scope is being pentagrid type. The oscillator coil can If the present receiver has an a.f.c. used, trim the second oscillator now for be one of the tapped permeability-tuned circuit and it is desired to retain this the most symmetrical response. If no types intended for shortwave receivers; feature, it can be done simply by leaving scope is used, tune in an actual signal or a 10.8 -mc i.f. transformer can be the tubes in. In this case we sacrifice the and adjust the oscillator for best quality modified by tapping one winding and trap, but except in local areas a single and lowest distortion. It will be found removing or shorting the other winding. trap will probably suffice anyhow; and that the oscillator peaks at three points: In any case., the whole oscillator circuit now, by taking the a.f.c. off the outboard at a point about 200 kc lower than 10.7 should be completely shielded and by- amplifier we can combine the new circuit mc, at 10.7 mc, and at a point about 200 passed as possible. If it can be placed with a.f.c. kc higher than 10.7 mc. The second posi- in a separate shielded compartment, tube The second i.f. channel produces no tion can be recognized by the beat note and all, it should be. Despite the most problems whatever either in construction with the signal. The proper position is valiant measures, however, it is alto- or adjustment. There are a lot of com- the one around 10.9 me since this is the gether likely that the 9th harmonic of ponents but if small resistors and cer- only one which will reduce the appear- this oscillator will be radiated and picked amic capacitors are used, room can be ance of harmonics in the r.f. range to up by the front end at about 98 mc. If found for them easily. The 1 -µf capaci- only one. this happens to fall in a spot occupied tor in the second limiter plate circuit The final step is to adjust the absorp- by a desired station, the oscillator can cannot be made smaller without loss of tion traps. Tune the signal generator to be moved upward or downward slightly low- frequency response. about 11.1 me and adjust one trap for -but not too much, or the 8th or 10th It will be noted that the detector out- minimum response. If this reduces the harmonic will appear at either the upper put is followed by a low -pass filter. This response to a point so low that it will or lower end of the tuning range. The filter is desirable if the amplifier which (Continued on page 84)

34 AUDIO DECEMBER, 1956

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G -E GOLDEN CO -AX 12 -inch Dual Coaxial Loudspeaker fj Loveliest of all -the gift of great music through the ears. Awakened for you now in new splendor by the magic wand of Combine a I _' inch woofer. a General Electric Hi -Fi. Here are components for a lifetime of superb inch tweeter. and musical enjoyment. Ideal for anyone who appreciates the finest. built -in electrical - The incomparable General Electric cartridge puts new brilliance in mechanical ero-- -,n, r -vstem. Handles 25 watts of power. Di-tortion free it your favorite recordings at modest cost. Ranging upward, you -II find response -40 to 15.000 cycles... General Electric speakers, the sensational 20 -watt Amplifier and Pre - Amp, and other superb components each adding in its unsurpassed way to a quality of reproduction famous in professional circles. Fortunately, all General Electric components are sensibly priced. Examine them at your local dealers, or write today for our free booklet of new Hi -Fi ideas. General Electric Company, Special Products Department, Section 844126, Electronics Park, Syracuse, New York.

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www.americanradiohistory.com Multiple Tape Copying

R. E. BAIRD

With the aid of a few simple chassis designed for a specific purpose, this station succeeded in reducing the time required in making multiple copies of tape recordings at a minimum of cost.

AFEW RADIO STATIONS and many in- Likewise 50 copying machines would be stitutions of higher learning have equally unreasonable. Depending on the inaugurated tape transcription individual requirements the number of 6.3V.o.c,. ERASE ERASE REC PLAY services for the purpose of disseminat- copying machines will lie somewhere AND B- BIAS QQ4 ing radio programs to be broadcast over between these two extremes. Ose a number of stations. Sometimes the The most obvious answer to the copy- B. ing problem is to buy as many tape CI distribution may be only a half dozen transport mechanisms and associated AUDIO stations but most generally the number amplifiers as needed. At the State Col- much gets higher. The problem of taking lege of Washington, KWSC, we did not a "master" tape and copying it many take kindly to the idea of buying so times becomes one of economics and many tape copying amplifiers when it time. If you need 50 copies of a 15- appeared that one amplifier might do minute program it would be ludicrous the whole job. to use one play -back machine and one The purpose of this article will be to copying machine for the whole process. describe two different setups that achieve , the above end, using specific equipment. The first system involves the use of Chief Engineer KWSC, Washington 3 State College, Pullman, Wash. six Magnecorder, PT -6 series, mechanisms. In our actual case we built the L entire amplifier including the equalizer J circuits. This was before the PT -7C am- r plifier came out. It would be advisable I at the present time to buy a PT -7C and i ó connect on a "home brew" final amplifier.

I I The solution is quite simple. You just _J build six push pull amplifiers with a t--- common input. Each amplifier terminates with a hi -fi output transformer feeding a recording head, as shown in Fig. 1.

1-71101 3 AUDIO Bias Oscillator Heterodynes INPUT L J The reader might think on first ob- o servation that all the heads could be r o driven from a single, more powerful amplifier. In the case of Magnecorders FROM this is not possible because each mecha- I 6 I PT -7C nism has its bias and erase oscillator self - 4 1 1 contained. Since more than one is being L J used the bias frequency varies slightly from machine to machine and hetero- Fig. 2. Block diagram of connections to dynes would be produced if record heads play heads of six recorders to permit were paralleled. audition of any one of them at will. Using separate final amplifiers did not completely solve the heterodyne situa- The output from the third head was tion. Using a common power supply for then fed through a six -way selector all of the oscillators created heterodynes switch to an audition amplifier so that Le about 20 db below zero level. To remedy spot checks might be made on each tape this, 50 -kc wave traps were inserted in in the process of copying. If a console each B+ lead. Each of these is composed with audition facilities is to be used in of a 10 -mh r.f. choke and a .001 -0 mica conjunction with the equipment the third Fig. 1. Six separate output stages fed capacitor (L, and C, in Fig. 2). heads can be sent through the selector by the same input transformer eliminate Some time after this system went into to a spare mike channel. This will re- the problem of interaction between bias operation, conversion kits changing the sult in loss of bass but still will suffice circuits. mechanisms to three heads were obtained. (Continued on page 78)

36 AUDIO DECEMBER, 1956

www.americanradiohistory.com now gives you .. . component convenience plus Beacon Tuning

FM-AM Tuner- Phono and Tape Preamp -20 -Watt Amplifier On One Chassis ... In One Handsome Enclosure

slightly higher 19 9 s'O Went of Rockies How welcome this will be to those of you who have been seeking an easier path to gen- and a 20 -watt amplifier ... plus the added uine high fidelity. For it is true, that many of accuracy and ease of Beacon Tuning. you have actually denied yourselves the thrilling performance of components - simply And then, Pilot designers styled an enclosure because of a disinclination to 'do it yourself'. for the modern home and set it off in deep burgundy and brushed brass. The result is Recognizing this, Pilot developed the fabu- so attractive that you'll want to show it off on lous HF -42. With one bold stroke, Pilot elimi- an open shelf or table top. nated the inconvenience of wiring and the chore of special installation. In the HF -42, To complete this truly fine high fidelity sys- Pilot embodied all the necessary high fidelity tem, you need only add a Pilot Companion or components - integrated on one chassis and other high quality speaker system. And with ready for use: a superb FM -AM tuner -a the inclusion of a changer or turntable, you versatile phono- preamp with full record and can enjoy record reproduction that tape equalization - dual tone controls - approaches the realism of the concert hall.

See your high fidelity dealer or write: Dept. CM-1

the P1o1 RADIO CORPORATION 37 -06 36th STREET, LONG ISLAND CITY 1, N. Y. IN CANADA: Atlas Radio Corp., 50 Wingold Avenue, Toronto 10, Ontario

A IDIO DECEMBER, 1956 37

www.americanradiohistory.com Jans /en

1 -.30 electrostatic tweeter AK-1 acoustic suspension woofer

On )larch 2, 1956, at St. Nark's Church, Nt. Kisco, The Audio League staged a musical de straution in which the recorded sound of an eolian- Skinner pipe organ was instantaneouslyously alternated with that of the Iice instrument.

The reproducing equipment .selected included four AR -1's and two JansZen's. Titis is snore of the press comment on the ('Petit: `Ille SatllnigÿReUreul (Druid Hebb) "Competent listeners, with trained professional ears. were fooled into thinking that the lise portions were recorded. and vice %ersa. ... The extreme low notes were fell. rather than heard. without any 'loudspeaker' sound. and the high notes drifted out naturally. without gising the impression of being forced."

AUDIO (Julian D. Irrsch) "Even where differences were detectable at changeover, it was usually not possible to determine which sound was Ike and which was recorded. without assistance from the signal lights. ... facsimile recording and reproduction of the pipe organ in its original environment has been accomplished.' a udlacraft "It was such a negligible difference (between lire and recorded sound) that. even when it was discerned. it was impossible to tell whether the organ or the sound system was playing!" . AR and Jans%eu speakers hare thatching grille cloths and wood finishes. No external crossover network is required for the two-the woofer and tweeter are simply connected in parallel. The JansZen contains its own crossover elements and level control, and the treble response of the :.R -l\\' fails oil. rapidly and uniformly, by itself. /'rice for the complete system, in mahogany. is x329, (Oilier hardwoods or utility !i,r;.li mailable.) Descriptive literature on request. Jans Zen AP" NESHAMINY ELECTRONIC CORP. ACOUSTIC RESEARCH, INC. Easton Road, Neshaminy, Pennsylvania 24 Thorndike St., Cambridge 41. Mass.

38 AUDIO DECEMBER, 1956

www.americanradiohistory.com Semi -Solid Corner Enclosure

H. P. FOERSTER"

Having once lived with a slate loudspeaker baffle, this reader has gone onward toward a more practical material, and in doing so he comes up with a cabinet which combines some of the tried and proven principles of several other designs.

SOME AUDIO READERS will recall my appeared to favor the larger aperture. solid enclosure described editorially Considerable experimenting was done in March '53 issue. As a result of with damping of duets, damping of that experience I devised the following holes, variation of number of holes, etc., enclosure for fitting my 18 -inch Baker but the configuration as finalized was speaker into a corner of my living room. decided the best by listening tests and Basically, it consists of a "modified -RJ- frequency runs with audio oscillator. distributed port -bass reflex" built in a From Fig. 3, it will be seen that the corner as shown in Figs. 1 and 2. The twenty -eight half -inch holes are concen- semi -solid feature is obtained by bolting tric through the front panel and mount- the front panel and mounting board ing board -thus the back emission of the (both cut from half -inch asbestos cement speaker has multiple exits of varying board) to birch hardwood corner posts path lengths -two RJ -type ducts of un- cut from 3 x 4" stock as per Fig. 4. The equal length, two distributed port areas, two back panels, the top, and the bottom and combinations of both. (cut from 4 -in. plywood) are then at- A good woodworker would no doubt tached as a necessary evil in order to fit the plywood into rabbited corner form an enclosure. Note that this con- posts but I used butt joints, casein -glued struction allows only two parallel faces and liberally put together with 11/2 -in. -top and bottom -which are reinforced wood screws. The asbestos -board panels by 4 -inch strips of 3/4 -in. plywood to are bolted to corner posts with ten 1/4 -in. form lips for the front panel to fit into. flathead stovebolts with lock washers Also, the top and bottom as well as the under the nuts. hack panels are liberally padded inside For mounting feet I sawed two three - with under -rug cocoa- matting. This re- Fig. 1. The completed enclosure, with the inch sponge rubber halls in half and baffle itself covered with a suitable grille cloth. glued the halves to the bottom panel. I 111.;1 Dr Marieauri SI., Montreal also glued two strips of 34 -in. square T.Q., Canada. sults in a negligible vibration as com- felt to the lid just behind the corner pared to none with the previous concrete posts to hold the enclosure away from job. walls and clear baseboards -thus the First, the cut -out in the front panel weight of unit holds it into the corner. was made approximately 70 sq. in. in Half -inch asbestos cement board is area and gradually increased to a final available in 4 x 4 ft. sheets. These weigh 160 sq. in. area shown as listening tests (Continued on page 80)

O 0 o o o

O 0 o o

Fig. 3. Dimensions of the asbestos - cement board which comprises \ the baffle.

- I/2" DIAM. Ó Io

e f - I L Fig. 2. With the "furniture" front panel MOUNTING 32" X 23" X %2 removed, the arrangement of baffle, BOARD distributed ports, and loudspeaker pro- FRONT PANEL 36 X 23" X ^t" tective screen can be seen clearly.

AUDIO DECEMBER, 1956 39

www.americanradiohistory.com A Folded Horn Design

RICHARD A. GREINER

The ways of folding horns are myriad -but there is always room for one more. This one gives excellent horn loading to two low- frequency drivers, and provides space for midrange cones and tweeters.

I 'Y BACK IN 1950 the author decided to look into the problem of designing a speaker system which would be superior to those then in common use. The object of any of the enclosures is to get the electrical power output of the amplifier into the room as acoustical power, and at the same time keep the over -all distortion of the system very low. The corner horn, which was then coming into use, seemed to be superior to any other type of speaker enclosure. A properly designed corner horn is able to meet the requirements of high Fig. 1. Front view efficiency and low distortion quite well. of the completed However, one additional requirement corner loud- which many corner horns do not meet is speaker cabinet. that of ease of construction. The reason for the complexity of construction is largely due to the length of the horn needed to couple a small throat area to the necessarily large mouth area with a smooth gradual taper. It seemed that it might be possible to simplify the construction of the horn by making it shorter, thus eliminating many of the tortuous turns and discontinuities usually present. These discontinuities are a source of unwanted resonance and give some horns a characteristic sound which colors the music being reproduced in an undesired and uncontrollable way. In order to meet the requirements of low - to be rated in a suitable enclosure and available in several speakers, while not frequency cutoff, the mouth of the horn then increase the audio power delivered always used, does provide for much more must be large regardless of the length. to it from a sweep generator until the linear operation of the speakers. The other factor controlling the cutoff speaker fails mechanically. The power is the taper of the horn. For a given rating is then set at that value of power mouth area and taper the short horn at which the speaker is destroyed. The Description must have a larger throat than the whole problem of speaker power han- longer horn. This means that possibly dling capacity and speaker distortion is For the horn to be described, Fig. 1, several speakers would have to be used a very difficult one since there are so it was decided to use two high -quality to drive the shorter horn. This fact is many parameters to control. One can 15 -inch speakers for the bass section. not necessarily a disadvantage as will be only hope that the speaker manufactur- These speakers have a power handling seen directly. ers will give the audiofan as much actual capacity totaling 70 watts and enable Even the best speakers are very non- test data as possible for individual eval- one to use a throat area of about 160 linear devices. If a speaker can be used uation. At best, an intermodulation dis- square inches. at a small fraction of its rated power, tortion of 1 to 2 per cent at a level of 1f the mouth area and the taper are the speaker cone will move very little 1 watt is attainable with a speaker rated both selected to give a 35 -cps cutoff it and that motion which does occur will at 20 watts. The average power that a is possible to make the horn only 52 be over the most linear part of its possi- system in a large living room may be inches long. It is easy to provide for ble range. There is no standard method called upon to deliver is only a fraction this length by using only one fold at the of rating speakers used by manufac- of a watt. However, there is no longer corner of the room. As can be seen in turers that is known to this author at much argument that peak powers of tens the diagram, the plan view of the horn present. One method which has been of watts are reached in peak level pas- is quite simple. All of the panels shown commonly used is to place the speaker sages. The necessity for using several are the same length -50 inches. This speakers to drive a short horn may now alone simplifies the construction. The College of Engineering, University of be seen to be an actual advantage in taper of the horn is approximated by Wisconsin, Madison 6, Wig. that, the large power -handling capacity suai_ lit

40 AUDIO DECEMBER, 1956

www.americanradiohistory.com Make this a Christmas long remembered- with full fidelity listening pleasure for the entire family

'LI /-IL

ire /co crcke speakers are available \ 5 ", 8" or 12" sizes in standard impedances. Priced from $6.75 to $59.98 Blue prints are available for the doityourself enclosure builder.

You will hear a remarkable difference in the clarity of voice coil impedance constant over the whole frequency Norelco *Full Resonance Speakers. In a single speaker. range: this avoids incorrect matching. High flux den- twin -cones reproduce low frequencies, middle range, as sities are obtained through the use of "Ticonal" mag- well as the higher frequencies extending beyond the net steel. audible range -without distortion. Norelco speaker- matched enclosures are scientifically designed acoustical boxes which enhance the excep- WHY ARE NORELCO FRS SPEAKERS tional tone qualities of FRS speakers; bringing out their SO EXCEPTIONAL? true performance values. Norelco FRS Speaker Enclosures are available in They have incorporated a number of technical refine- three sizes to match the characteristics of the speaker ments which are evident the moment you listen. The air in use. Supplied in either mahogany or blond, these en- gap has been made long so that the coil is completely closures incorporate a removable base permitting the enclosed in an even magnetic field at all times. A cop- enclosures to be placed horizontally or vertically to per ring has been fitted into the deep air gap to keep the suit any room arrangement or decor.

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UDIO DECEMBER, 1956 41

www.americanradiohistory.com distortion is low. The system described coasts most of the time and there is no listening fatigue. That this design is versatile is witnessed by the fact that a scaled up model of this horn using two 18 -inch speakers was built by a friend of the author and gives astounding response and realism. It is hoped that the description of this simple and rugged system will lend encouragement to others to build a reliable and adequate sound system and then to listen to and enjoy the music of their choice.

Jan. 23 -25, 1957-Very Low Frequency Propagation Symposium, National Bu- Fig. 2. Plan view of the horn -loaded cabinet, showing the two mid -range cones in reau of Standards' Boulder Laboratories, the return sides, two tweeters on two front panels, and the position of the 15 -in. Boulder, Colorado. Sponsored by NBS woofers. Boulder Laboratories and the IRE Pro- fessional Group on Antennas and Propa- gation. folded horns. Though the actual dimen- feedback amplifiers designed by the Feb. 4 -8 -West Coast Convention of the sions of the horn are not at all critical, author deliver 40, 20 and 10 watts to the some features of the construction are. bass, mid, and treble ranges respectively. Audio Engineering Society, Ambassador The structure must be solid. The main Crossover points of 350 and 4000 cps Hotel, Los Angeles. Annual banquet on exterior of the horn should be made of are used. evening of Feb. 4 in Cocoanut Grove; 1 inch laminated or other heavy wood. papers presented on Feb. 7 -8. Grant The internal partitions may be made of Performance Graham, Triad Transformer Co., Venice, inch panels. It is essential that the Calif., section chairman. 3/4 listening volume behind the speaker be tightly After to this system for a long time, it was found that there is sealed off in order to provide the proper Feb. 6 -9-Los Angeles High Fidelity and almost no point at which the music is too loading to the backs of the speaker Music Show, presented loud. This frequently heard phrase is by the Institute cones. of High Fidelity Manufacturers. Am- The usually directed at systems which are finishing of the front of the horn bassador Hotel, Los Angeles. is largely a matter of personal taste. In the horn a made 2 shown, panel of -inch Feb. 15 -18 -Sam Francisco High Fidelity mahagony planks glued together and and Music Show, presented by the In- finished into a curved shape for an stitute of High Fidelity Manufacturers. earlier speaker enclosure was used. Then. are two triangular shaped regions whirl: Iiotel Whitcomb, San Francisco. are used to house the midrange speaker.,. These speakers bounce their sound oft March 18 -21 -IRE Annual Convention and of the wall. The tweeters used must be Radio Engineering Show. The Coliseum, of the completely enclosed type, either New York City. horns or cone type with enclosed shields over the back, and may be mounted in Apr. 9- 11- Fourteenth Annual British the front panel of the horn. In the horn Radio Component Show, Great Hall, pictured, two Jensen tweeters are Grosvenor House, Park Lane, London, mounted behind the grill cloth at an 37 W. 1, England. Admission by ticket only, angle to one another to provide wide - obtainable from the Radio and Electronic angle high -frequency coverage. The bass Component Manufacturers' Federation, speakers are Jensen P15-LL types. It is 21, Tothill Street, London, S.W. 1. desirable to use amplifiers with low in- Fig. 3. Section through A -A cf Fig. 3 to show flare at top and bottom of main ternal impedance to drive a horn. In horn. Apr. 12-15 -The London Audio Fair, 1957. order to accomplish this there are no Hotel, W. speaker crossover networks used with Waldorf Aldwveb, London, C. this system. Instead, three amplifiers are being played at much lower than realistic used to drive the three ranges. An elec- intensities, not because of the loudness tronic crossover with level controls for but rather because of the distortion in April 28-May 3 -81st Convention of the the individual sections in order to adjust the system. To a point, music sounds Society of Motion Picture and Television for the different efficiencies of the speak- fuller and better when it is played at Engineers. Shoreham Hotel, Washington, ers is used. Quite conventional triode close to concert hall intensities, if the D. C.

42 AUDIO DECEMBER, 1956

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microvolts for 20 db of quieting. Less than 1 For microvolt sensitivity for AM. Separate front ends Pride and for FM and AM. Adjustable selectivity for AM and variable AFC for FM. Inputs for 72 ohm and 300 ohm balanced antenna. Super- smooth flywheel tuning. Shielded and shockmounted. Practicality ... Multiplex and cathode follower outputs. Less Cabinet, $169.50 Specify THE FISHER FM -AM Tuner Model 80 -T Unequaled, the 80 -T is the most advanced FM- AM Tuner with complete professional audio control facilities. Employs identical FM-AM circuits as the S 80 -R. The first tuner -control chassis with a sepa- dR rate tape head playback preamplifier (with NARTB equalization.) Preamplifier equalizer can be used with lowest level magnetic cartridges. Six record :c equalization settings. Separate Bass and Treble Controls. Four inputs. Cathode follower outputs to recorder and amplifier. t Less Cabinet, $199.50 Usually ... when a music lover purchases a FISHER high fidelity product, he does so for pride, for quality, for personal satisfaction. On the other hand, it is gratifying to know that if he preferred - FISHER he could have chosen FISHER, the THE - FM FM leader in the field, purely on the basis Tuner Model -90 of economy. For it has been proven time The Finest FM tuner Made! The FM -90 definitely and again, that FISHER, with the best sets the standards for the tuner of tomorrow ... and in technological advancement and beauty outperforms any existing FM tuner! Micro - accurate tuning combined with extreme of style, is most practical to own. sensitivity and flexibility. Two meters indicate signal strength

and center -of- channel. Extra -wide 1 megacycle FISHER Modules afford the most bandwidth. Full limiting on signals os low as 1 complete versatility for practical, microvolt. 72 and 300 ohm antenna inputs. In- step -by -step assembly of a high terchannel muting control. Completely shielded fidelity music system! and shock mounted. Outputs for amplifiers, tape and Multiplex. Cathode FISHER functional concept of unit - follower permits leads up design offers the user the most economical to 200 feet. Less Cabinet, $149.50 means of achieving the ultimate in sound reproduction! Start Now With

THE FISHER FISHER FM Tuner Model FM -40 For Discriminating Listeners! A remarkable instrument, beautifully designed, yet modest in cost. Stable circuitry and simplified controls make the FM -40 exceptionally easy to use. Meter for micro - accurate, center -of- channel tuning. 72 and 300 Depending on individual requirements - ohm antenna inputs. Sensitivity is 3 microvolts whether you are just beginning your high for 20 db quieting. Outputs for amplifier, tape fidelity hobby, or whether you seek and Multiplex. Cathode follower output permits to improve an existing system - plan leads up to 200 feet. the first step with a practical view toward Less Cabinet, $99.50 the future. Devote your budget to basic components. In that way, you can realize immediate listening satisfaction ... with quality FISHER equipment. Moreover THE FISHER you can add to it later, with the same high AM Tuner Model AM -80 level of quality. A Precision AM Tuner! The AM -80 combines the If you start with phono - choose from the pulling power of a professional communications wide selection of FISHER quality amplifier receiver with the broad tuning necessary for high models ... later, add a tuner for FM, fidelity reception. Meter for micro- accurate tun- AM or both. Or ... ing. Less than one microvolt sensitivity for maximum output. Three -position adjustable band- If you start with radio - choose a profes- width. Dual antenna inputs Three inputs, cath- sional tuner and amplifier from the ode follower output. Ideal for all areas including wide range of FISHER models later, those beyond FM station range. ... add phono facilities, buying the best Less Cabinet, $119.50 quality manual or automatic player your budget permits.

For the Best Present . . . Attractive wood cabinet in Blond and Future . . . Plan with FISHER or Mahogany is available. www.americanradiohistory.com FISHER Exclusives That Make a World of Difference !

Exclusive FISHER Features provide that added measure of control to satisfy all f - listening requirements. Here is flexibility that obsoletes old fashioned hi -fi. Here is * Ö FISHER FIDELITY ... it makes a TN; rkNA I.IE 1=1 11111 r'orld of difference. y J l Progressive Engineering At Its Superlative Best...

THE FISHER Model 90 -A THE FISHER Model 80 -AZ THE FISHER Model 55 -A 90 Watt Audio Amplifier 30 Watt Audio Amplifier 55 Watt Audio Amplifier A full 90 watts of gentle power ... capa- Incomparable FISHER amplifier with Pow- Plenty of power for your present - and ble of reproduction characteristic only in er Scope, a visual Peak Power Indicator. any possible future needs. The world's THE FISHER. With less than 1/2% distortion More clean watts per dollar than any ampli- foremost oll- triode amplifier - a laboratory at full output, the 90 -A performs with breath- fier in its class. Less instrument functionally in than 1/2 / distortion designed for use taking, life -like clarity. Two power sup- at 30 watts. Uniform response within 1 db the home. Full 55 watts at less than 1 plies. Exclusive FISHER Performance Moni- from 10 to 50,000 cycles. Exclusive Z -Matit distortion. Exclusive FISHER il:uminated tor for exacting operating conditions. Re- and Power Scope Indicator conveniently Power Monitor indicates average audio

sponse within 0.1 db from 20 to 20,000 mounted on panel. Hum level better than power. Uniform response within 1 db from cycles. Power take -off for unpowered 95 db below full output. Damping factor 5 to 100,000 cycles. New Z -Matit variable auxiliary equipment. Exclusive Z-Motic. of 26. Outputs for 4, 8 and 16 ohms. damping control provides three times the Output for 8 and 16 ohm speakers. S99.50 range. Damping factor of 31. Outputs Damping factor in excess of 16. for 8 and 16 ohms. S229.50 S169.50

l :

THE FISHER Model CA -40 THE FISHER Model 80 -C THE FISHER Model 20 -A Master Control -Amplifier Master Audio Control 15 Watt Audio Amplifier Complete in every respect - the remarkable Model CA -40 Master Control Amplifier Containing features found only in profes- A laboratory standard amplifier of tradi- with ToneScope I A 25-watt amplifier with sional studio consoles - the Master Audio tional FISHER quality, designed to meet the complete Audio Controls - you actually see Control matches any power amplifier. Pro- requirements of the most exacting user. all of the control settings, Less than 1% vides professional phono and tape -head Low in cost, high in quality, the 20 -A boasts distortion at full output. ToneScope panel equalization. Full mixing and fading faci- advanced design throughout. Less than lights up for ready reference. Direct tape- lities for from two to five channels. Seven 0.7Y., distortion at full output. Uniform re- head playback and microphone preampli-

Inputs. Two cathode follower outputs sponse within 0.1 db from 20 to 20,000 fier. Uniform response within 1/2 db from Preamplification and equalization directly cycles. Power takeoff for auxiliary equip- 10 to 90,000 cycles. Cathode follower re- from tape playback head. DC filaments for ment. Damping factor of 16. Outputs for corder output. Outputs for 4, 8 and 16 non -measurable hum level. Self -powered. 4, 8 and 16 ohms. ohms. Complete with cage. Less Cabinet, $99.50 $59.50 S139.50 /Mr FISHER RADIO CORPORATION 21 - 29 44 DRIVE LONG ISLAND CITY 1, NEW YORK

www.americanradiohistory.com FISHER `FIRSTS' - Milestones in Audio History 1937 FIRST High fidelity sound systems featuring a beam -power amplifier, 1953 FIRST Universal Horn -Type Speaker Enclosure for any room location inverse feedback, acoustic speaker compartments (infinite baffle and any speaker system. and bass reflex) and magnetic cartridges. 1954 FIRST Low-cost electronic Mixer- Fader. 1937 FIRST Exclusively high fidelity tuner, featuring broad-tuning 20,000 FIRST Moderately- cycle fidelity TRF. 1954 priced, professional FM Tuner with TWO meters. 1937 FIRST Two-unit high fidelity system with separate speaker enclosure. 1955 FIRST Peak lower Indicator in a high fidelity amplifier. 1938 FIRST Coaxial speaker system. 1955 FIRST Commercial CotltrulChassis with mixing facilities. 1938 FIRST High fidelity tuner with amplified AVC. 1955 FIRST Correctly equalized direct tale -head playback preamplifier in 1939 FIRST Dynamic Range Expander. tuners and master controls as well as a separate preamplifier. 1934 FIRST Three -Way Speaker in a high fidelity system. 1956 FIRST To incorporate Power Monitor in a home amplifier. 1939 FIRST Center -of- Channel Taming Indicator. 1956 FIRST Alf Trmssitorized Pre -Amplifier. FIRST Preamplifier -Equalizer with selective phonograph equalization. 1945 1956 FIRST Dynamic limiters in an FM tuner for horse use. 1948 FIRST Dynamic Range Expander with feedback circuitry. FIRST Performance Monitor in a high quality amplifier for 1949 FIRST FM -AM Tuner with variable AFC. 1956 home use. 1952 FIRST 50 -Watt, all-triode amplifier. 1956 FIRST FMAM tuner with two meters. 1952 FIRST Self -powered Master Audio Control. 1956 FIRST 90-watt amplifier especially designed for home use. 1953 FIRST Self -powered, electronic sharp cut -off filter system for high 1956 FIRST Complete visual indicator for bass, treble, filter controls and fidelity use. record equaliz:.t' .

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THE FISHER Transistor Preamplifier TR -1 The first all -transistor high fidelity product! Absolutely zero hum and zero microphon- ism. Powered by battery or AC power supply. Consumes 0.0217 watt. Choice of four inputs. Handles lowest level magnetic cartridges. RIAA phono equalization. Flat response for mike ± 0.5 db, 20 to 20,000 cycles. Maximum gain, 48 db. Three trans- POWER istors, printed circuit wiring. Four controls. TAPE RECORDER AMPLIFIER $27.50

THE FISHER Mixer -Fader Model 50 -M Mixes two signal sources of equal or varying amplitudes. Permits smooth, noiseless fading from channel to channel. No insertion loss, extremely low hum and noise level. High impedance input, cathode follower output. High signal -to -noise ratio, negligible distortion. Self- powered, with AC switch. Completely shielded. Beautiful plastic cabinet, brushed -brass control panel. TAPE RECORDER 519.95

PHONO THE FISHER MASTER AUDIO Hi -Lo Filter - Model 50 -F CONTROL Electronic, sharp cut -off filter system for TUNER suppression of turntable rumble, record scratch and high frequency distortion -with an absolute minimum loss of tonal range. Low frequency cut -off points (Flat, 37, 70, 120 cycles) at a slope of 10 db per octave. High frequency cut -off (20, 10 and 3 Kc) at POWER MODEL o slope of 20 db per octave. Self- powered, AMPLIFIER 50 -F jewel pilot light. S24.95

MAGNETIC CARTRIDGE THE FISHER

Preamplifier - Model PR -6 TAPE A self -powered unit of excellent quality, PLAYBACK MODEL moderate cost. For use with any low -level PR-6 magnetic cartridge, tape deck or microphone. Two triode stages, high gain. Exclusive feed -back circuit permits long output leads. Fully shielded. Uniform response, 20 to 20,000 cycles within 2 db. RIAA equalization for phono. NARTB for POWER tape. Hum level 60 db below I volt. AMPLIFIER 510.95

AUDIO ACCESSORIES FOR EVERY APPLICATION Individual Technical Bulletins are Available on All Models - Write Today FISHER RADIO CORPORATION 21 -29 44 DRIVE LONG ISLAND CITY 1, NEW YORK www.americanradiohistory.com Stabilizing Transistor Amplifiers

RICHARD H. SMALL

Another approach to the problem of stabilizing transistors so that they will continue to perform predictably over a long period of time. The author shows how the typical stabilizing circuits are developed.

SINCE THEIR INTRODUCTION some years such a circuit around a CK722 transis- ago, have been transistors applied TABLE I tor. For this transistor, a typical value to many fields of electronics. At- of ß is 15. If we select V =10 volts, and i, , ma. v.., volts tempts to replace vacuum -tube circuits 5 i,.= 0..5 ma, we can calculate with circuits utilizing transistors have 10 0.34 6.6 met with frustration for several reasons. 13 0.41 5.9 N =V 5 volts, 15 0.51 4.9 1. The transistor, unlike the tube, is a 18 0.62 3.8 current amplifying device. 24 0.93 0.6 2. Transistors, as yet, cannot be pro- 31 0.98 0.2 R2 = 10,000, duced with uniform properties. 3. Transistor properties vary with tem- R, = 20112 =300,000. perature. The grounded emitter current gain is The measured values of collector current One of the worst blows dealt by well and collector voltage for this circuit are meaning people to the popular accept- shown in Table I for several transistors ance of transistors is the publication of b with different values of ß. For the last circuits which tend to accentuate the Thus the collector current will be two transistors, the collector voltage is shortcomings of transistors. Actually, so low that operation as an amplifier transistors are capable of excellent, de- =ßib=ß1l' will be seriously impaired. pendable performance when used with , It is easy to see the analogy between proper circuitry. In this article, a very The collector voltage will be this circuit using fixed base current bias- popular transistor amplifier circuit will ing, and the vacuum -tube circuit using be shown to be basically undependable 1-- i,.R,= i' t,= \1 -ß :) fixed grid voltage biasing. This vacuum - because it does not allow for normal tube circuit is well known to be unstable transistor variations. An improved cir- For maximum swing each side of the with respect to changes in tube trans - cuit will then be presented. operating point, the collector voltage conductance. First, let us consider the popular should be one half of the supply voltage, Since we have thus far found an anal- grounded -emitter amplifier circuit shown or ogy between the transistor circuit of in Fig. 1. The poor dependability of this Fig. 1 and the vacuum -tube circuit with circuit has led many experimenters and 1- fixed grid bias, perhaps we can develop manufacturers to believe that transistors r, = . a better transistor circuit by analogy are perverse little devices that are far with an improved tube circuit which is inferior to vacuum tubes. Therefore already well -known. Such a tube circuit The transistor is biased as follows: R, 1 contains a resistor in series with the ^ , Since the base to emitter voltage is R_, cathode, of such a value that the voltage negligible in a transistor, R, determines and the value of R, must be developed across it by the passage of the base current it,: the plate current is equal to the required 1 R (Contin,uvl on page ;ti) tb=l{ , Now we can see that for the. fixed base 11SO Rubio St., _9ltadena, California. current provided by this circuit, the collector current and collector voltage are dependent on ß. This property. the grounded -emitter current gain, will vary eonsiderahly among any group of identi- cally labeled transistors, often as much as a factor of two to one. Also, the value 01' ß is temperature dependent. The result is that the operating point will vary with temperature, and replacement of the transistor may cause the circuit to become completely inoperative.

Fig.l. Typical circuit for a low -powe Fig. 2. By the addition of the voltage transistor as shown in many of the ex divider R, -R2, the potential of the bass Example perimental applications. No provision is is held fairly constant even though the made for stabilization. To illustrate this effect, let us design emitter current may change appreciably.

AUDIO DECEMBER, 1956 47

www.americanradiohistory.com Features of Patent -Licensing Agreements

ALBERT WOODRUFF GRAY

The interest in patents and in court decisions affecting the validity and effectiveness of them is particularly important to the inventer, especially considering the most recent decisions. The author gives a resume of some of the earlier law on the subject.

Snit by the Zenith Radio Corporation these patent pooling agreements, in hold- become essential to his alienees for the against the Radio Corporation of ing that these other companies were assertion and vindication of their ex- America, Western Electric Com- licensees not owners and hence, not in- clusive rights. If he transfers the un- pany, and General Electric Company terested parties. divided portion of the entire interest in asked a court decree that thousands of "Each party to the agreements, in- the invention he thereby confers upon radio patents pooled by these companies cluding American Telephone and Tele- his transferees rights equal to his own be held unenforceable against Zenith. graph Company and Westinghouse Elec- in all respects in the invention and re- In answer, Radio Corporation of Amer- trie Company, shares \dtln the nominal ceives them into copartnership with ica and the others charged Zenith with owner and independently exercises in its himself in the monopoly which is now the infringement of these patents. fields the vital right to grant or withhold as essential to their protection as it was To this Zenith maintained this patent licenses and the concomitant right to to his." pool was "part of a plan or conspiracy collect and retain under such licenses, In the formation of this patent pool to dominate and monopolize in violation as well as to control and share, any rein this litigation however, the agree- of the anti -trust laws." As a consequence coveries in infringement litigation and ments between the parties were not as- of these acts, it contended, the owners to grant releases for past infringements signments of patents but "non -exclu - of these patents were abusing the privi- with respect to all the patents in the sive licenses." leges of the Federal patent system and pool."2 had forefeited any right they otherwise Then resting its determination of this Non-exclusive Licenses might have had to the protection of contention of Zenith on that century old Of this feature of this controversy these patents by the courts from in- decision of the Supreme Court, the Fed- the court said, "The term `non -exclusive' fringement. This it followed with an ap- eral District Court said of the distinc- is a key description of the extent of the plication that brings into sharp outline tion between the licensees and the as- patentee's conveyance, be it applied to a the distinction between the licensing of signees of a patent, vital right such as sublicensing or a a patent and its assignment. "Two constituent property elements lesser fringe benefit under a patent. It Two other companies, the American of distinct source, nature and divisible spells the difference between the pat- Telephone and Telegraph Company and content inhere in every patented inven- entee abandoning the field or any part Westinghouse Company, contended tion. One is the property in the inven- of it in favor of his alienee or retaining Zenith, were co- owners of these pooled tion itself -the right to make, use or the paramount rights to his monopoly patents and that. as they were interested sell the patented article personally or to which his patent entitles him. To my parties in the claim of infringement and through others -the second is property mind it cannot be a door through which had not been made parties to the suit, in the monoply-the right effectively to one can enter into co- ownership. A the claim for infringement should be prohibit others from practicing the in- true non -exclusive conveyance is incon- .dismissed. vention or profiting therefrom without sistent with co- ownership status in pat- In a decision of the United States the owner's consent. ents. rendered over a century ago it was "Means of transferring these two "If it were., any bare license would held that those parties are essential to property rights have pertinence here qualify for ownership. A non -exclusive a lawsuit "who not only have an interest and vary greatly. Rights in the inven- grant, in fact, demonstrates the op- in the controversy but an interest of tion itself may he transferred either posite. By it a patentee expressly such a nature that a final decree cannot separately or together, upon one person negates the exclusion of both himself be made without either affecting that or many, and each may, independently and all others to whom he may later interest or leaving the controversy in of the others, use the rights received. choose to grant rights of the same or such a condition that its final determina- The monopoly is indivisible except as to (Well greater calibre. Having conveyed tion may be held inconsistent with locality. although several assignees may only non -exclusive rights, the patentee equity and good conscience. "' jointly hold the undivided interest in the retains all others and through them con- On the authority of this old ruling patent. tinues his dominion over the monoply." Zenith pointed to the omission of these "When the patentee conveys the ex- Recently another patent licensing other interested companies and de- clusive right to make, use and sell the agreement. of which there are legion in manded a dismissal of the infringement invention he has no longer any occasion the industrie s of this country, came be- charge on this ground of a failure to for the exercise of the prohibitory fore the Supreme Court for considera- include all those interested in the con- powers created by the patent, while they tion in a suit to recover unpaid royalties. troversy. This non -exclusive license agreement, The court said of the provisions of 1 Shields v. Barrow, 58 U. S. 129, page covering 570 patents and 200 applica- 139 (1854) of 11' -20 Seventy Second Drive, Forest 2 Zenith Radio Corp. v. Radio Corp of tions the Hazeltine Research, granted Hills, New York Am., 121 F.S. 803 May 20, 1954 (Continued on page 56)

48 AUDIO DECEMBER, 1956

www.americanradiohistory.com Engineering Artistry Craftsmanship

Systems Concept New three-way speaker system with 15 inch resistance damped enclosure

Response from 40 to 18,000 cps Electrical crossovers of 300 and 5,000 cps, Power 30 watts Net Price $249.00

New three speaker system incorporating a resistance controlled enclosure Response from 50 to 15,000 cps, Power 20 watts Net Price $129.50 eT

/ New corner system utilizing three speakers and a resistance controlled enclosure Response 50 to 15,000 cps, Power 20 watts Net Price $119.95 The famous :atenoid now offered by its originators with new improved speakers Response from below 30 to beyond 18,000 cps Three -way sy item with full bass horn FROM THE AUDIO LEAGUE -"We have never heard o and electrical crossovers of smoother overall sound. The balance of lows, middles, 300 and 5,000 cps and highs, was well -nigh perfect." Power 30 watts, dimensions 371/2" H :: 29" along wnll from corner Net Price $395.00 '/uÁ,PIZP Two -way bookshelf speaker utilizing an isothermal backvolume All LEE speakers available in mahogany, blonde and Response from 70 to 15,000 cps, walnut pressure laminate finishes Power 'i 5 watts Net Price $69.95 L.E.E. INCORPORATED The laboratory of electronic engineering

NEW YORK AVENUE, N.W., WASHINGTON 1, D. C. NA. 8 -3225 www.americanradiohistory.com woofer roue and a super -tweeter-the former extending the range downward and the latter extending it upward. The tweeter Equipment Report is installed against the front baffle with an air -tight gasket so the high pressures normally generated in a bass -reflex enclosure Heathkit Speaker System (SS -1 I and Range Extending Sys- do not damage it -as they would be sure to do if the delicate diaphragm tem 1 SS -1 B )- Tannoy "Variluctance" phonograph pickup of the super -tweeter were open in back. cartridge- Stentorian line of loudspeakers and accessories The range extending system, shown in Fig. - is sanie I, the width as the basic unit, and Additional information on the AMI model R -1250 amplifier. is 29 ill. high. It is designed to serve as a base for the smaller unit, and when the two are connected together the dividing IN Tills -1Gt: of "do- it -vinlrself :nt it itv, the builder acquires a four-way system networks (two of them) in the range ex- there does not seem to be any end to that performs remarkably well, and he sloes tending system divide the frequency range what the ambitious and enterprising it with surprisingly little effort-except into three parts -the lowest being fed to (mksIs i,lual may put together, either from the finishing. Lucky is he whose furniture the woofer and the highest to the super- scratch wherein he actually does all the is of the painted type, for he can avoid tweeter, while the midrange band is fed work himself-as AUDIO renders have done notch of the work of rubbing ;uul polishing. to the smaller cabinet. Thus the woofer with amplifiers and speaker enclosures for works from 33 to 6110 cps, the 8 -in. cone trom 600 to 1600 cps, the compression years -or with the aid of a prepared kit The SS -1 "Basic" System which has much of the more difficult work driver and horn from 16011 to 4000 cps, done already. In the normal Bourse of building the and the super -tweeter handles all the fre- The assembly of pre -cut wood parts into complete Ileathkit speaker system, it is 'Iwmcie. above 41111) cps. various types of furniture makes it con- likely that a person would begin with the siderably easier for the average individual basic system (the term `basic" is ours, Construction -auol toy- that eve mean one who is not since Ileath offers no such simplification) \ I t he wood pieces are eut to size and equipped with power saw, router, ,joiner, which consists of a ducted -port bass -reflex I.. veled or grooved as required. It should planer, and the many other items which enclosure measuring 111._. in. high, 23 in. be possible to put the smaller unit together grace the hobby shops and wide and in. deep. Its ap- mail order cata- 1Ili external easily in less than two hours, and the big complete a desired pearance is shown in 2. em- logs-to unit with the Fig. This unit filly goes together in about four speaker -both of assurance that it will not look "home- ploys two mechanisms-an 8 -in. these figures exclusive of sanding and fin- made" when is put in cone :11111 a compression it the parlor along- driver with an ishing, of course. The two front frames side the products exponential both of Grmml Rapids. For- Imru, of special design, are completely assembled and require only tunately, there are many speaker systems and both built by ,lessen. By the use of final sandpapering which to be ready for the fin- are available in kit form, and by a series capacitor, the high- frequency unit ishing operation. The internal construction and large they work out to be -lust as satis- does not function 1600 until approximately of the basic system is shown in Fig. 4. factory as their " store- itoughten " coun- cps. When complete, the system will cover terparts. 511 ±5 the range from to 12,000 cps within Electrical Circuitry Not all, however, have all of the addi., according to specifications, and there vantages of the Ileatbkit speaker system- is certainly audible output over titis range. Fign'n 3 is a schematic of the two units that of starting with a comparatively in- ill working form, with the smaller system expensive unit lvhieli gives good quality of Range Extending System shown enclosed in dotted lines. The divid- sound in itself, and then adding to it the ing networks are of the constant- resistance means for reproducing perhaps an octave The larger section of the entire systemm type, with the parallel configuration. A at the top end and probably more than consists of another ducted-port bass -reflex switch (not shown in the schematic) per- that on the bottom. The final result is that enclosure which houses a heavy -duty 15 -in. mits testing of the separate sections, and

Fig. 1 (left). The Range Extending system occupies a sturdy and solid ducted -port bass -reflex enclosure which houses a 15 -inch woofer and the little super- tweeter, as well as two dividing networks with crossovers at 600 and 4000 cps. Both employ air -core coils and paper capacitors. Not intended to serve as a complete speaker system by itself, this unit is designed to work with the basic speaker system, Fig. 2 (below) which consists of an 8 -in. cone and a compression driver with a short exponential horn. The smaller unit may be used by itself, however, to cover the entire range.

50 AUDIO DECEMBER, 1956

www.americanradiohistory.com P. In my country I'm the top hound, but is my master's pet for sound.

If you have a tape recorder, or hope to acquire one for Christmas, improve its performance by purchasing

a CAPPS Condenser Microphone. Highest quality at the lowest prices. Models available in low or high impedance.

Model illustrated is Studio CM 2250A, with chrome swivel.

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4UDIO DECEMBER, 1956 51

www.americanradiohistory.com Without question, the performance of 10 db- before the final dropoff, and the LEVEL this system belies the simplicity of its con- listening teats show this by a ringing tend- ADJUSTING struction. Some slight experimentation ency at the higher frequencies. This is L -PADS with the small system leads us to the be- called by some a "peaky" response. None SUPER lief that the cabinet needs some internal of that is noted in the Tannoy, however. TWEETER dumping, since it seems to sound better The Tannoy should be considered a low - (in our environment) with about four level pickup, since its output is 21 mv for square feet of Ozite for padding, making a stylus velocity of 10 cm /sec. This means sure to avoid getting any padding adjacent that the maximum output from this pick- 4000, to the duct. Lacking the Ozite, it is prob- up will practically never exceed 40 mv, NE"WORK r- "BASIC" UNIT able that the Kimsul used in packing the even on the loudest records. Certain pre- kit would serve equally well if tacked care- amplifiers will overload when the pickup fully on the inside of the cabinet. output is too high, and if this condition is HORN It is difficult to evaluate the need for suspected, the Tannoy would be a good UNIT padding in the large cabinet, but it seems choice. likely that it might help to reduce any The cartridge is a turnover model, fitted vibration of the cabinet walls. Actually, with two easily replaceable diamond styli, 8" very little such vibration is noticed because one for microgroove and one for standard. CONE of the self- bracing construction, but we Response on both sides is practically iden- luIve a preference for some damping in tical both in shape and level. The unit is O L_ COM any speaker enclosure. However, without designed to work with a load of 47,000 any padding whatsoever, the complete sys- ohms, and of itself has a d.c. resistance tem will certainly be considered an im- of 775 ohms and an inductance of 300 mh, INPUT provement over the vast majority of sys- resulting in a source impedance of 2050 I5" tems now in use-as might be expected ohms at 1000 cps-a figure which is of no CONE from the lineup of speaker mechanisms importance with conventional input cir- and the design of the cabinets. D -18 cuits to the preamplifier. Optimum track- o ing force, as far as intermodulation is IN concerned, is 6 grams, so that the unit may 600, NETWORK THE TANNOY be used with changers without having to "VARILUCTANCE" CARTRIDGE work at a stylus force above the optimum, which we consider the point at which the Fig. 3. Simplified schematic of the com- One of the older standbys among the intermodulation distortion is minimized, many phonograph plete system. Section enclosed in dotted pickups on the market and it is well known that changers rarely is the Tannoy "Variluctance" cartridge, give thoroughly satisfactory operation with lines is the system in the small cabinet. which has always seemed to perform with stylus forces of less than 6 grams. D -19 individual level- adjusting controls make audible smoothness whenever it has been it possible to balance the system quite ac- demonstrated at the audio shows. The tests THE STENTORIAN LINE OF curately, although the balance between the show why it "sounds good," since there is LOUDSPEAKERS 15 -in. woofer and the lower-midrange 8 -in. almost no peak in the performance curve AND cone depends upon the built -in sensitivity throughout the entire range, and the slight ACCESSORIES of the two mechanisms. boost at the top is rounded off so that there One of the largest of the imported lines Performance is no noticeable coloration. of loudspeakers is the Stentorian, which Measurement of pickups is likely to re- ranges all the way from a duplex 15 -in. While no attempt was made to make sult in a portrayal of the response of the model down to a simple and inexpensive absolute measurements on the system, it particular record under test. In the first 6 -in. cone, with excursions into the area was compared with another of accepted place, most good magnetic pickups will of super -tweeters, crossover units, and con- high quality on an A -B test basis and the turn in n smooth curve up to about 10,000 stant impedance controls. Heathkit system is judged to compare fa- cps, since practically none of them has We have had an opportunity of testing vorably. Our simple teat for the lowest any resonance below that frequency. There- four of the speakers 12 if -a -in. full -range frequency that a speaker system will re- fore, one record is used for a series of unit, Fig. 6, and 10- and 8 -in. cones, and produce as a loudspeaker (that is, not like testa, the resulting curves will all have the the 8 -inch high -frequency model housed in a sail flapping in the wind) is to play the same general characteristics. In our test- an attractive wooden box which would scale portion of side 2 of "The King of ing of pickups, the Cook Series 10 disc is serve well as a tweeter in conjunction with Instruments" organ record, Vol. 1. The used -the one designed for 78 rpm. This an existing speaker deficient in highs. scale, which appears about the center of brings up the question of Vinylite reson- The 12 -inch model, HF1214, has a rather the side, commences at 16 cps and pro- ance, since all measurements are made at deep cone which is laminated (as all the gresses upward in the scale of C. In using 78 rpm and yet the pickups are used at Stentorian cones we have seen) from a this test, one observes the first note at 33%. However, as with many other "semi - conventional paper cone and a treated cam- which the tone has a definite musical pitch rigorous" tests, if the same equipment bric which gives a certain degree of stiff- and ceases to be just noise. By counting and methods are used for all, the tests may ness that is desirable to prevent breakup. up from C, this note may be located very be considered directly comparable. The cambric extends beyond the paper sec- easily, and the frequency of the lowest note The curve of Fig. 5 shows the response tion of the cone and serves as the sur- which has a musical tone may be said to measured from a new Cook record, which round, while the treatment makes the outer be the lowest frequency that the speaker shows a difference in response of 3 db at edge airtight as well as retarding reflec- will reproduce. Using this method, the note 10,000 cps over one that had been in use tions from the rim. One feature of the at which the system became musical was for some time, but both resulted in smooth cones in all of the full -range speakers con- B. which is approximately 30 cps. The curves. By direct comparison, some pick- sists of cutting a number of 1 % -in. holes lowest we have ever heard on any system ups will be found to have a definite reson- in the cambric before it is laminated with is G, or 24 cps. ant peak -in many cases of as much as Fig 5. Response curve for the Tannoy car ridge, run from the Cook Series 10 test record. Output at 1000 cps is 21 mv for a s ylus velocity of 10 cm /sec.

111111111M1111111MSIII 1111II=IIIIII=11111111II Fig. 4. Internal IIIIII111111INI111III construction of the Io 111111111111=111111

tl small system. SS1 IIIIIIIIII1IIIIII o 11111111111 Rr::. 1111111III11=Inin1111111111111Ì111110 la R111111111Míi1111IIMIIIIIIIM u IIIII!111111III 1!:d1IIIM11111111111111I11II 11111111M11111111111111111111111=

1,0000C VC 1.01 OE CON0

52 AUDIO DECEMBER, 1956

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The Coodmans Axiom 80 is a 10- tion is clean and articulate and the inch, twin -cone, full range loud- 'highs' smooth to 20,000 cycles. All speaker, whose performance, in a of this is accomplished without the proper enclosure, is as astounding use of special `tweeters' and elabo- as its unique design. rate crossover networks. The most revolutionary advance Power handling capacity of the embodied in the Axiom 80 is its single Axiom 80 /ARU system is achievement of free cone suspen- entirely suitable for use in most sion -the theoretical ideal that per- home systems (8-12 watts, contin- AXIOM 80 LOUDSPEAKERS mits the cone to move as a true uous program material; 4 -6 watts, piston at low frequencies, without rms sine wave). Where greater each $68" restriction and without distortion. power handling is desired, two ARU ENCLOSURES Another direct result is that the Axiom 80 loudspeakers may be fundamental resonance of the used together in the Model B -2800 Model C -1800 24 "h x 18 "w 'x 16 "d ( for 1 Axiom 80) Axiom 80 is only 20 cycles -lower ARU Enclosure or four may be than that of any other commer- used in the Model A-4800. 5925 cially available loudspeaker. No multi channel system, however Alodel B -2800 26 "h x 20 "w x 20 "d The new ARU Friction Loaded elaborate or costly, can surpass in ( for 2 Axiom 80s ) Enclosure represents the perfect performance these dual and quad- 6685 ruple Axiom 80 /ARU systems. solution to the enclosure require- Model A -4800 30 "h x 24 "w x 20 "d ments of this superb reproducer. ARU Enclosures are now available (for 4 Axiom 80s) Axiom mounted in a in easy -to- assemble kits, supplied The 80, Mod- 7 0 el C -1800 ARU Enclosure, will re- complete with the necessary pre- 49 produce true bass fundamentals cut lumber, grille cloth, padding, slightly higher west of Rockies down to 20 cycles -with no 'hang- glue, hardware, instructions and For complete details, see your hi -fi over' and without peaks above that the all -important ARU Acoustical dealer or write to Dept. WM -1 frequency. Mid -range reproduc- Resistance Unit.

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AUDIO DECEMBER, 1956 53

www.americanradiohistory.com the paper cone, thus reducing the stiffness high- frequency speaker mounted in a pol- sistor, and the output power was measured in parts of the cone so that there is little ished mahogany enclosure measuring 13 in. for the distortion test on the basis of this chance of any undesired local vibration in wide, 10% in. high, and 7% in. deep. This load. the cone itself throughout the midrange. model would serve well to enhance the AMI engineers claim, however, that These cutouts are known as "midrange high- frequency- response of an existing since the terminals may feed into a max- stabilizers." loudspeaker without the need for modify- imum impedance of 20 ohms, the amplifier The 111'1214 has a wider excursion range ing the present enclosure. It would only - should be measured under these conditions, than most models of this size, being nearly be necessary to add one of the crossover and the power calculated accordingly. 1/2 inch, :nd it is apparent that the voice waits available to result in a complete two - While we do not agree altogether with this coil does not get out of the magnetic field way system. The range of this unit is idea -since it is not likely that the ampli- throughout the entire travel. The ampli- claimed to be from 1500 to 17,000 cps, and fier will be used with 20 -ohm speakers - tude of the resonance peaks of all the output is measurable above that range, we must admit that there is some merit in Stentorian models tested seem to be rela- with the response smooth to the ear; no their position, and in those cases where tively high, which night indicate that en- pronounced peaks were noticed. closure design would be rather critical. Two horn -loaded tweeters are included The frequency of the resonant peak of the in the line, with model T -12 being shown HF1214 was measured at 30 cps, which is in Fig. 7. This model employs a 9 -lb. mag- low for a 12 -in. speaker unit. The output net, and offers considerable efficiency to i3 of normal loudness for a given sound the range from 3000 to 20,000 cps. The input, indicating an average efficiency. '1' -10 is much less expensive, and is only Inn a listening test with the speaker claimed to extend to 16,000 cps. mounted in an infinite baffle -in a wall Crossover writs are :mailable for im- between two large rooms-duality- was pedances of 15 ohms :and crossover fre- good, and the low resonant frequency quencies of 5110, 15110, and 3000 cps. No worked to give an apparent boost to the level controls are incorporated in the net- very low frequencies. The high end was works, but constant- impedance balance smooth and pleasant to the ear. controls are separately- available, not only for 16 ohms, but also for 4 and 8 ohms. HF 1012 One of these units is shown in Fig. 8. Each consists of a wire -wound T This is a 10 -in, model of similar design -pad with ten steps of approximately 1 db per to the 12, but equipped with a voice -coil step and an additional position. arrangement which may be used at 4, 8, "off'' The or 16 ohms depending on the connections. switch proper is attached to a recessed Four terminals are brought out, the two plastic housing which mounts in a 21/ß -in. sections of the voice coil being paralleled for 4 ohms, either one used alone for 8 ohms, and the two sections connected in series for 16 ohms. The comments regarding this model on listening tests would be essentially the sane as those for the 12 -inch speaker, with Fig. 8. Constant -impedance T -pad used the 35 -cps resonant frequency aiding in for balancing levels between speakers, or for remote speakers in a complete home installation. the speakers are more closely matched to the amplifier the available power output could surely be calculated by the manner suggested. In an case, the amplifier was tested again with a 20 -ohm load, and the power output calculated on this basis, with the result shown in Fig. 9. While the original Fig. 7. Model T -12 Super Tweeter -a measurement with the amplifier feeding heavy -duty horn leaded tweeter for the into a 16 -ohm resistive load indicated a range from 3000 to 20,000 cps. power output of approximately 12 watts at 2 per cent IM distortion, the new measurement shows an output of 19 watts at the hole, leaving the surface essentially flush. same amount of distortion. A studv of the entire Stentorian line In the of will indicate any interests accuracy of presenta- Fig. 6. Stentorian model HF1214, a 12- that practically desired tion of this type of information, it is felt combination of speakers only- Ile' selected, that the optinnim conditions may well be inch extended range speaker with a together with the necessary dividing net- resonant frequency of 30 cps. considered as standard for test purposes, works and level controls to provide a wide whether or not the amplifier is to be used and varied range of speaker systems, in the low -frequency response. Over -all per- under those exact conditions. We trust the addition to the duplex concentric models presentation of the new distortion curve formance is such as to indicate that the designed to cover the range from 20 to unit would work satisfactorily in con- will indicate a desire to be fair in the test- 20,000 cps with the convenience of mounting procedure, and that it will give a stricted space, provided it was matched ing only a single mechanism. D -20 to the enclosure carefully. truer picture of the performance of what is unquestionably an excellent unit. HF -812 FURTHER INFORMATION ON This S -inch speaker is similar in design AMI R -1250 AMPLIFIER to the 10 and 12, and shows a resonant frequency of 50 cps. It is also equipped Audio engineers at AMI differed front AMI 1 -1730 with the two -section voice coil that will its in the measurement of the R -1250 am- AMPLIFIER match 4 -, 8 -, or 16 -ohm outputs. plifier, reported in this section in the Sep- A similar model in appearance is the tember issue, and as a result we made a HF816, which employs a 31/2-Ih. Alconax reeheck in the manner which might be magnet in contrast to the 2 -1b. magnet said to be more correct. This amplifier is used in the 812 and 1012 models. This equipped with an unusual output trans- model was not tested, though it would be former because it is designed for use with expected to offer some advantages over multispeaker systems in addition to the more the lighter model -as it should, since its common single -speaker installation. SO cost is more than twice as great. The secondary of the transformer has five porn EWFrt terminals, and the load range from 12 to The Cabinet -Model Tweeter 20 ohms is covered by one pair of termin- Fig. 9. Output vs. IM distortion curves als. In our normal method of measurement, for AMI R -1250 amplifier measured into Model T -8160 consists of an 8 -inch this pair was fed to a 16 -ohm load re- a 20 -ohm load.

54 AUDIO DECEMBER, 1956

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www.americanradiohistory.com Now! A hi -fi manual so complete it is used by PATENT LICENSING technicians, yet so practi- Travel the cal that every layman will LIro,n page want it! complete Sound die licensee permission to use these pat - -tits its the manufacture of its "home CHARLES FOW- products" and in return the licensee spectrum with LER, publisher of agreed to pay Hazeltine Research a High Fidelity mag- minimum annual royalty of $10,000 on azine and Audio- its sales of radio broadcast receivers. TANDBERG ... the craft, is recognized In its defense this licensee contended as one of the world's outstand- that this agreement was illegal and un- world's finest ing hi -fi authori- enforceable as a patent monopoly. ties. Now, in his "The mere accumulation of patents, new book, he tells no matter how many, is not of itself tape recorder! everything there is illegal," said the court. "This record to know about hi- does not the fidelity. In clear, support incendiary yet easy-to -follow lan- vague charges that the patentee uses its guage, he gives detailed explanations of accumulation of patents `for the ex- such subjects as "transient response" action of tribute' and collects royalties and "intermodulation distortion," and by means of the overpowering threat also answers more elementary questions about loudspeakers, binaural sound, and of disastrous litigation.' even selecting the right draperies for "This licensee cannot complain be- better acoustics. With more than 300 cause it taust pay royalties whether it pages, an 8 page index, and 113 illus- uses Hazeltine patents or not. What it trations and diagrams, it is a book that no hi -fi enthusiast should be without! acquired by the agreement into which it entered was the privilege to use any or HIGH FIDELITY all of the patents and developments as A Practical Guide by Charles Fowler it desired to use them. If it chooses to use rione of them it has nevertheless con- $4.95 tracted to pay for the privilege of using THERE are specific, step -by -step direc- existing patents plus any developments t Lions for selecting loudspeakers and resulting from the patentee's continuous choosing a cabinet for finest results. Am- search. We hold that in the licensing of plifiers, control units and preamplifiers, the use of patents to one engaged in a tuners, phonograph pickups, record changers, and turntables are all thor- related enterprise, it is not of itself a oughly covered, too. For the advanced misuse of patents to measure the con- enthusiast who'd rather build than buy, sideration by a percentage of the licen- 3 SPEEDS 1 78, 334, 71/2 I.P.S. this book provides instructions and data see's sales."' for making your own speaker enclosure, STYLED TO FIT ANY DECOR dividing networks, and coils. You learn Another feature of these patent li- how to get the most out of manufactur- censing agreements became the subject BALANCED PLAYBACK, AMPLI- ers' specifications -and what to look for of an infringement action brought sev- FIER AND SPEAKER when buying. eral years ago by the Western Electric ABSOLUTELY NO WOW OR The book clearly shows you: Company. In this instance a notice on FLUTTER AT ANY SPEED -how to test components before buying the carton containing an amplifying de- -how, and what, to buy on your budget vice was in part "The sale of this device You too can experience the wonder of -how to assemble them for smoothesi carries a license only for (1) talking complete sound dimension with the world operation machine use, (2) radio amateur use, famous Tandberg recorder. Off the air -how to control them for truest sound (3) radio experimental use and (4) recordings mode ... "just fooling around -how to eliminate mysterious hums and radio broadcast reception and only at home," ore truly mirrored by the won- other noises where no business features are involved." der of electronic faithfulness, built to get new from your pres- -how thrills Use of these amplifiers in theaters in right into this amazing tope recorder. ent equipment violation of this license restriction had been held by 10 DAYS' FREE EXAMINATION the lower courts to be an The versatile 3 speed Tandberg infringement of the amplifier patents. McGraw -Hill Book Co., Inc., Dept. AUD -11 will more than pay for itself in 327 W. 41st St., New York 36, N. Y. When that determination was sustained tape savings as you discover the Send me Fowler's HIGH FIDELITY for 10 by the Supreme Court of the United days' examination on approval. In 10 days, I this re- will remit $4.95 plus few cents for delivery States, it was said of such restrictions superior performance of rosis, or return book postpaid. (We pay on the use of patented articles, its lower speeds. delivery costs if you remit with this coupon; corder at 'ante return privilege.) "That a restrictive license is legal PRINT seems clear. The patentee may grant a Ask Your Dealer For A Demonstration Name license upon any condition, the perfor- Write For Full Information To: address mance of which is reasonable, within the reward which the patentee by the City Zone .... State grant of the patent is entitled to secure. Company TANDBERG The practice of granting licenses for a 10 East 52nd Street Position (Continued on page 66) New York 22, N. Y. l'or prive and terms outside U. S :Trite McCraw -Hill Int'l., N. Y. C PLaza 9-7190 AUD-11 3 Automatic Radio Mfg. Co. v. Hazel- tine Research, 339 U. S. 894, June 5, 1950

56 AUDIO DECEMBER, 1956

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BOX 966 DARIEN CONNECTICUT EXPORTS: ELECTRONICS MANUFACTURERS' EXPORT COMPANY. PLAINVIEW. NEW YORK

AU 9I0 DECEMBER, 1956 57

www.americanradiohistory.com aid those who have not doue much con- structing of equipment, the placement of the major components will be described. AUDIOCLINIC ? ? The power transformer, T,, is mounted at the upper left corner of the chassis; below it is the rectifier tube, V,, with the JOSEPH GIOVANELLI filter capacitor, C4, to its immediate right. The front edge, then, is taken up by the Mixer channels and rectifier, filter capacitor, and the three de- adjust this for minimum hum. coupling capacitors, The impedance at the input of each micro- such as C,, C,,, in the Q. I am interested in first stage. obtaining a mixer phone channel is 5 megohms, Behind each dual decoupling tvhich will suitable for capacitor enable me to mix the outputs of crystal or dynamic microphones. Matching is mounted a shielded noval tube two or three microphones - socket. On the and some high transformers should be used if low-imped- left edge of the front apron level sources such as crystal pickups and ance microphones are is mounted the on -off switch, with the pilot tape recorders. Most the called for. The im- lamp of units available pedance at the high -level inputs is 100,000 directly above it. The remaining space for this purpose, capable of giving gain ohms. A is taken up with the three potentiometers enough voltage divider would therefore be to feed a standard tape recorder needed if the 500,000 impedance such as R corresponding to their respective input, arc too expensive. Do required vacuum tubes. Proceeding you know of for most crystal or ceramic cartridges is to from the trans- any circuit which will satisfy my needs? be arrived former end of the rear apron, there are Roy Jacobs, at. mounted Bronx, N. Y. Mixing action is accomplished the line cord grommet, fuse post, in the hum- balancing potentiometer, A. Figure 1 shows a schematic of such a plate circuits of the three amplifiers by R then the mixer. It has three separate channels, and virtue of their being connected through jacks for the third stage, and second stage, each one can be used with either micro- separate isolating resistors, as indicated and first stage (J, and J,) one above the other. All jacks are insulated from the chas- phone or high -level input. J J, and J, by R,, to a common coupling capacitor, C,. are the microphone inputs, while J, is the It is possible to incorporate sis, as are the filter and decoupling capaci- more than tors. A ground phono input for the first stage. J, is the three channels, though there will be a bus is grounded to the output jack. When a high -level source is shunting load chassis at J and this bus runs through effect of resistance, plus the all ground connected to any of the three inputs de- capacitances of the tubes which will have terminals on the jacks and filter signed for it, the mike input corresponding an adverse effect upon the frequency re- capacitors. When wiring all other circuit to that channel is disabled by the switching sponse, as more and more channels are components, make all ground connections action of the jacks used. This was done in added. to the bus, never to the chassis. This type order to prevent the shunting action of the The of wiring was done to minimize hum unit is built on a 5 x 10 x 3 inch pickup. mike stage from adversely affecting the aluminum chassis. If the unit is to be frequency response. R, is a hum balancing portable, a foundation chassis may be used, Aside from the method shown in the potentiometer. Turn the volume up on all eliminating the need for any further hous- schematic in Fig. 1, there are two alter- ing. native means for connecting the filaments Layout: There is a considerable num- of the three tubes. By connecting these 3d:0 Newkirk Ave., Brooklyn J, N. Y. ber of components to be mounted and, to filaments to a five -volt source rather than a six -volt source, noise output from the mixer is lowered, with some sacrifice in gain. The filaments could also be connected to a d.c. source rather than to alternating R6 current, which would result in a considerable reduction 22,000 in hum, although the hum CIA is quite low anyway. -0/450 The unit may 0.1 J4 be constructed at a cost of ff RIO between forty and fifty dollars, depending R9 22,000 upon components 12AX7 6 the used. V2B V2A 47,000 .. CIB JI 2 7 - 40/450 Linear Speed Recording ODA RII .02 CM1©l IF-o-v1J Q. Ii-hat i.- linear spc,d recording? Allen 0.22 Meg. Jensen, Lakeland, Florida. A. Inn order to explain what linear speed C6 o recording is, it will be necessary to point 25, 25 25,25 out some of the properties of conventional disc recording. Assume that a recording is being made on a 12 -inch blank, at 33í/s rpm. At the start, the circumference of the disc is IDENTICAL WITH V2 CIRCUIT approximately 38 inches. Thus, it follows that at this point, the disc material passes under the recording needle at the rate of 20 inches per second. This is, of course, an instantaneous value, since the circumference is constantly growing smaller as the IDENTICAL needle moves toward the center. As the rate WITH V2 CIRCUIT at which the material passes under the needle decreases, the high- frequency response is gradually attenuated. This hap- 11I I C45 pens for the following reason: Suppose the frequency is 15,000 cps. One cycle, there- 20 450 FI 51 Itr- fore, takes 1 /15,000 of a second. Assume now that the circumference is such that 15 ó C4A inches per second is passing under the cut- VI 3 ting stylus. During one cycle, 1 /1,000 of 6X1 . . -f""20/450 8 an inch has passed under the needle. The ( size of the stylus for microgroove work is one mil (1 /1,000 of an inch). Note that the size of the needle is equal to the C5 .05 4 amount of material comprising one cycle at 15,000 cps. As the circumference becomes still smaller, the needle size becomes greater than that of a single cycle, with the result that this frequency and those above it can no longer be recorded. The Fig. 1. Simplified schematic of three -channel mixer -amplifier which is flexible in application. (Continued on page 81)

58 AUDIO DECEMBER, 1956

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Al DIO DECEMBER, 1956 59

www.americanradiohistory.com EDWARD TATNALL CANBY FOUR B'S AND AN H part from the opening of several new and to practice. There's no need to play staccato Beethoven: Piano Sonatas Ops. 109, ultra- modern buildings on the M.I.T. campus, on such an instrument when the registration 110, in which these recordings have been made. is well chosen. 111. Glen Gould. Columbia ML 5130. The question comes up, of course, how Moreover, the recording organist must never Having teed much advantage does Unicorn derive from forget that his mike is close, hears all, and off his recording career, hardly the very can minimize any blur that may present itself. out of his teens, with Bach's tremendous specially designed acoustics of these "Goldberg buildings, a church and an auditorium that You don't play long -distance style to a close - Variations," Glen Gould moves mike. youthfully on to the very will knock your eyes out, as the pictures and up ultimate in piano description hacks All of which means the recording Baroque music. with the brash modesty of a really on the of these recordings indicate. The series is consciously focussed on organist must do a bit of adapting, to a new gifted, but very young musical talent. The situation. three greatest giants of the classic sonata this architecture, the publicity and the record I don't think this one did enough literature! The finest notes alike feature it heavily. thinking on these lines, before the tapes thing that can he said Well, I've always started to roll. here is that there is no failure. On the con- looked askance nt "mod- trary, Gould's playing ern" architecture as a medium for better re- Still in all -it's a nice record. I'm Just is interesting from cording acoustics, at least music. splitting a few hairs. start to finish, his approach both remarkably in (Speech knowing and is another thing.) The modern style is all pleasantly naive. against success. What music Beethoven: With all the genius imaginable, these son- needs, generally. Symphonies #4, #8. Minne- atas, is a well- broken -up, mellow, live acoustical apolis Symphony, Dorati. the last mature works in a life -time of situation. Older European buildings of num- creative experience, music of an elder- states- erous styles are ideal. The more hideous Mercury MG 50100. man sort, are not likely to be fully penetrated of our own Victorian monstrosities in a few short years are just I heartily recommend these two perform- of youth. No criticism fine for recorded sound. Gew-gaws, decora- ances as the most satisfactory in a long time, of Gould at all ; he makes a remarkable beginning. worth tions, much carving in wood or plaster or in spite of some relatively unplastic playing, anybody's attention. But the stone (good or had, it makes no difference), a lack of feeling for the longer phrases and long years of work by older pianists a maximum of irrelevancy and /or complication Schnabel, Kempf, - rhythms that seems to be characteristic of Myra Hess -can't help but in the reflecting surface, that's what record- Dorati's work. show in their varied performances of these ing likes best for music, and the modern styles same The Fourth and Eighth, the two "prob- sonatas. Eventually, Gould may well just don't provide it. even with the fancy ad- lem symphonies," have caused the join then[, after n greatest couple of million playings. justable liveness panels now often used. conductors no end of anguish. Somehow. these 'Columbia's rather brilliant piano blends The trouble is that architecturally we in- oddly, at close works tend not to "come off," and you don't range, with Gould's irrepres- sist today on (a) simplicity and (b) sym- bear them too often in concert compared to sible humming. At least, unlike some famous metry. We like flats, curves, sweeping lines. the others. pianists and conductors, be hums in tune! And when we come to roughnesses, for break- Yet this doesn't mean that the music is ing up of sound, we still tend to let them less than first rate -far from it. Somehow Music at M.I.T.: Beethoven: fall into regularity. We can't bring ourselves here, perhaps simply by being uncomplicated Piano Sonatas to create the marvellous irregularity, the dy- Op. 109, Op. 110. Ernst Levy. and direct and natural, Dorati has bit the namic shape -rhythms, of the Gothic cathedrals bullseye in both works. Phrasing or no, Unicorn UNLP 1033 or the wood- carved interiors of the past. And subtleties or no, the over -all feeling for each so our sound, in modern buildings, tends to he Here's a real piano Blunderer, is so convincing that, in these performances, of the old not only over-dry but, worse, over -simple in there's every reason for the two works to school, a miracle man with Beethoven in a its reflection pattern. style that is strangely of another become favorites among record collectors. time, of, It's a compliment to Unicorn to be able to The recording Is superb, matching Dorati's say. the very early 20th century. I've heard say that the sound of the music recorded in Ernst Levy play Beethoven forthright, vigorous approach with its brilliant, before, in person, these ultra- modern halls is well up to normal close -up sound. hut I think these are his first LP records. recording standards. That, to my mind, is an He does the thing in the grand style and he's accomplishment in the face of unusual diffi- Brahms: Symphony #1. Pittsburgh Sym- a big interpreter any way you look at it, culties. (And the earliest recordings made though he'll also be somewhat "controversial" here were acoustically phony, Wm. Steinberg. Capitol P8340. as far as not so good.) But as listeners and critics are concerned. to there being any marked advantage in all You always expect something interest- These playings are a far cry from the can steely, this modernity, I'd say No. Not In the hearing front Steinberg. whatever he tackles. He's powerhouse performances now the ing. an enterprising and very musical conductor. general rule. They are romantic, large, florid, The Handel Organ even Concertos? Lovely music This one, the umpty -umpth Brahms First, is eccentric; everything is first of all felt, and a nicely balanced, rich hi -fi sound, as I different with a vengeance, but consistently even when the sense of the music is oddly in- noticed with pleasure in several demonstration and musically so. I'm not sure whether I want terpreted, even when the Levy pedal seems to rooms at the Hi -Fi show last fall, where this to swallow the differences or not -but there's add a bit too much of a grand blur to the record had been passed around for trial. An no doubt I'm going to have to play this again, Beethoven shape. (How seldom do the new outstanding job. acoustically. and maybe still again. Good. pianists use pedal, these days!) But on more leisurely listening I have a The most striking difference here is one of No, not all the experts will be pleased. But few reservations. The performance seems to tempo. Brahms, for instance, didn't write the nobody could deny these records a big. swash- me only so -so, rather stiff and unpinstic, con- high -speed scherzi common in symphonies buckling place in the pianistic ranks, and sidering since Beethoven except in his earlier, pre - those who aren't so familiar with the exuberance of the material. A bit the music on the academic side- though Handel is Irre- symphony music. Instead he turned to slow - will particularly enjoy their expressiveness, pressible and the life of the music will not be ish, lyric song movements often labelled their utter lack of mechanistic technique - denied; It gets through. "grazioso " -graciously. There's one of these projection. I wonder, too. about the organist's staccato in this symphony and Steinberg has whomped playing on the fancy new Baroque -style organ up the speed on it. Very odd at first, but then Music at M.I.T.: Handel: Organ Concerti. with the ultra- modern pipes. (See picture). again, he might, he just might have some- That is a trick easily learned by organists who thing. Is It just habit, what we are accus- Lawrence Moe, organ; Unicorn Concert must cope with soggy organs that simply do tomed to. that makes us react with a quick Orch., Klaus Liepman. not cut through the big reverberations of No? So It goes in other respects with this Unicorn UNLP 1032 church buildings. Play staccato, then, shorten stimulating reading of an old -time warhorse. the notes, separate them, and beat the echo. It's always good to have what is usually "Music at M.i.T." is a good title for this But the whole point of the Baroque organ called "new light" thrown on a familiar piece series and a fine idea; the inspiration came in is that it does cut through reverberation by like this and it always stirs many to wrath. virtue of its special tone colors -the great This one will do just that -but I Ilke it, pro- 780 Greenwich St., New York 14, N. Y. secret of the old organ builders, now restored visionally.

60 AUDIO DECEMBER, 1956

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AU 10 DECEMBER, 1956 61

www.americanradiohistory.com Bach Organ Works, Vol. 2: Vars. on "Sei nicely. We're catching up-all of us, not just MORE Gegrüsset, Jesu Gutig "; Prel. and Fugue the aesthetes. This one is a specialty, a ballet score based in C; Passacaglia in C Minor. Anton on ideas from Tchaikowsky. It's a superb Heiller. Epic LC 3261. combination. The Tchaikowsky element in it makes for easier listening There are three recordings of the Complete for the person who isn't yet on sure ground in modern music, but Organ Works now current ; 11'estmtnster's is well aware that maybe it has something. On NEW with I 'tit 11'einrich is also appearing in sag - men', whereas the other hand, the Stravinsky "beat," the IDEAS... that by Helmut Walcha in modernly brassy orchestration here from ibe AnI.ive Series ( and there, Decca) carne out com- the jazzy fragmentation of ideas, add a stream- plete in one enormous release (but is avail- lining to Tchaikowsky that to many another General Electric able in separate discs). Bach being Bach, ear will be wonderfully welcome. then, it would surely be possible for a reviewer Whatever your viewpoint, the chances are to spend the rest of his life comfortably that this long score will come to be a favorite studying Bach on the organ ! The material after you've let it sink in a bit. A big work, justifies it, but time and space don't allow. and superbly recorded with the composer at I'm not overly excited by this set, so far. the controls. Perhaps organ playing on records, especially -FI at such lengths, poses HI its own standards of variety and inner treatment of organ music Stravinsky: Concerto for Piano I'm inclined to think so. I feel, simply, that- and this organist's work tends to become monoton. Winds; Capriccio for Piano and Orches- ous in the listening. to sound rather orgeny" tra. Nikita Magaloff; L'Orch. de la Suisse and a trace academic. Not by any means much. Romande, Ansermet. London LI. 1392 The playing is intelligent and reasonable as to tempos, without eccentricities, not chilly and Stravinsky-'s piano writing is thoroughly soulless a bit. (Some organists are that.) modern. He uses the instrument deliberately It's just that, in the long run, the listener's for percussive effects, rather than the old attention may wander afield. It takes positive song -like music; he arranges to have his piano hard work in Bach to keep the listener listen- hanged hard, just as do jazz pianists. That ing, as we all know -the old man (lid very is the Twentieth Century approach, in a very little in the way of superficial attractiveness. wide variety of piano music, popular as well Let's not exclude the organ itself and the as "classical." recording from our consideration. This is The Concerto for Piano and Winds is a a good organ, but again, not particularly bril- real humdinger of an Early -Twenties opus. In TRANSIS -TUBE liant or startling, as here recorded. The sound two seconds flat you could date it yourself, is conservative and so is the microphoning: whoever you are. 1924! It's amazing how, at a PRE -AMP... at a safe distance, so to speak. distance, everything now begins to telescope I like the variations on the tune "Sel together, Cershwin and Stravinsky sound transistor power circuit Gegrusset" best. The well- known Passacaglia alike and are obviously of the same epoch. It's is good but not overly exciting. n pleasant accident that this brassy, noisy The new General Electric 'l'Ii:kNSIS- 1920s music is extremely good for hi -fl pur- TUBE pre poses and makes marvellous recording mate- -amplifier is distinguished for Bartok: Sonata for Two Piancs and Per- rial, as of today. Try it and you'll see. super- sensitive preamplification -lower cussion. Music for strings, Percussion and The Capriccio, a sort of piano concerto, Is a bit later, hum and noise with no microphonics- Celeste. Soloists, 1929. It's atore serious, more Pro Musica Chamber "classic," less raucous but still with the hard, uses no battery. Built around one NPN Orch., Stuttgart, Rolf Reinhardt. tvlgy contours of the Twenties. This piece has been quite non -junction transistor and one high - Vox PL 9600 widely played and was recorded years ago on 78 by the Boston Symphony and gain double- triode 12AX7. Handles just These iivo pieces neatly brought together that perennial Boston pianist, Jesus -Maria about every magnetic cartridge known. ny Vox, are related in their extraordinary use Sanroma. That's where I first got to know it. of permission in "chamber" style small en- An interesting facet of this recording is sembles of TRANSIS -TUBE pre -amp contains terrific hitting power. The "Music the peppy 1920s treatment from that long - for Strings, Percussion and Celeste" is already bearded built -in RIAA curve to deliver flat fre- conductor, Ernest Ansermet. Ills familiar to hi -fi record collectors in other ver- earlier Stravinsky, "Petrouchka' and the like, quency response from sions, notably that on Capitol that came out tended to be a bit slow -paced, almost old fash- some years ago ioned. modern LP recordings. Only and made a good name for But there's none of that here; the music $2195 itself. comes out as snazzily as you could imagine. The Sonata, a far more furious work -un- Recording is ffrr's very best and excellent for believably furious and very exciting -bas the music, big liveness and close -up coloration. pretty h resisted attempts to record it Superb, big -bussed piano tone. until now Vox once issued a memorable radio air -check of this work as played, 'way back, by Bartok himself and (I think) his Stravinsky: Apollon Musagètes. Renard. wife. It was pathetically feeble -and a net- Solo voices, L'Orch. de la work recording at that. The pianos sounded Suisse Ro- like bells, the percussion was almost inaudible, mande, Ansermet. London LI. 1401 so completely did the recording mechanism Here are two more works in the London- "break up" at the appalling noise. There Ansermet serles. "Apollon" is another ballet probably has never been composed a more of the Twenties, 1928, but again a very special fiendishly demanding test of recording tech- kind of music, entirely for string orchestra. nique than this work ! It is the ultimate in It makes a wonderful companion piece to sheer transient music. "Baiser de la Fee" (above), which because TWEETER ... In view of this, you'll find \'ox's recording of the Tchaikowsky element in it also has quite astonishing. indeed, the fact that this much lyric writing for strings. and cross -over network assembly record can be played from beginning to end full - If you want string range, to know how a orchestra without noticeable blasting or break- should sound at its very best, let the team of Here's a new Tweeter and matching up is a fine tribute to the totality of today's Stravinsky- Ansermet-London show you, here. record -reproduction technique, from mikes cross -over network for hooking into pres- and The music is gorgeously composed for strings, tape right through to the loudspeaker at home. the playing is done with the utmost in ex- ent systems. converting single speakers Leave it at that -I won't attempt an pansiveness evaluation and careful ensemble, the record- to dual jobs, of the music except to say that it ing is one of the finest of string sound I have etc. High -quality, versatile will simply blow you out of the room with unit for yet to hear. If you want to try two Stra- independent tweeter needs. its fantastic frenzy whether you like it or not. vinsky middle -period discs, take this one .\ real masterpiece. -fi Iii or no. in ease you are and the "Raiser" disc, above. You won't do interested, and I find it marvellous t i'-tem ing. Tweeter $1795 Network better. $1395 The part of one side left over is devoted to the oddly comic semi -ballet of 1917, "Renard," a piece about Renard fox See these new General Electric MIDDLE STRAVINSKY the and the silly developments cooster who is tempted to fly down off his Stravinsky: The Fairy's Kiss ( "Le Baiser de at your dealer's. or write for free copy of our perch by the fox's wily flatterings. A new new Hi -Fi booklet. General Electric Co., la Fee "); Complete Ballet. Cleveland kind of singing, this. and at first you may Special Products Department, Se, lion Orch., Stravinsky. Columbia ML 5102 think it's all just yelling-but there's a fine, steady rhythm and a cockeyed witless quality R44126, Electronics Park. Srraruxe. \. Y. We're now re- discovering St raviusky- of the to it that suggests the grotesqueness of ani- middle period, of the Twenties and Thirties, mals masquerading as humans -talking. and it's a pleasure. Re- discovery for Rogress /s Our As/ /nporldnl Produc/ me, any- Only trouble here is that London doesn't In- how, but .something new for a lot of people clude a text for you to follow. Silly every- who will now find, to their surprise, that this thing depends on what's going on at the mo- GENERAL ELECTRIC slightly raucous, slightly jazzy in- between ment. There are several other records (in Stravinsky stilts today's ears remarkably various languages) which do include texts.

62 AUDIO DECEMBER, 1956

www.americanradiohistory.com Stravinsky: Chamber Works 1911 -1954. Soloists, Conducted by the Composer. Columbia ML 5107

This one straddles the middle period of Stravinsky's life, but I'll toss it into the pot here, even so. The title is slightly misleading; all the music but one piece is for voice with instruments. One side goes to early music, around the time of World War I, the other side to quite recent work, from the 1950s. You'll need some background idea of Stra- vinsky's very consistent and unique use of the human voice before you can plunge whole- heartedly into this. As he uses the piano in a new fashion, percussively, so he treats the voice instrumentally, setting the word -syllables in an instrumental fashion, rather than according to their spoken accent and shape. This makes for an oddly sing -song effect on first hearing (as in "Renard," too) but in the end you will come to respect it mightily for its musical logic and expressiveness. The songs are genes. mostly very short, sung by voices that are markedly unlike the usual concert and opera singers. and nearer to the "popular" singer. The earlier works have been newly instrumented by Stravinsky and these are in effect their first performance. Note particularly the moving "In Memorian Dylan Thomas" (195.1), set for trombones. string quartet and tenor to a poem by Thomas, who was to have worked with Stravinsky on n joint project at the time of his death. Incidentally, the late works here, several songs and the instrumental Septet, show Stravinsky experimenting in the higher mathematics of the "Twelve-Tone" school of thought, as will he apparent if you read Rob- ert Craft's detailed notes- Inversion, retro- grade and the other mathematical transposi- tions are everywhere-hut if you don't hear them in a literal way, don't be worried. These devices are Intended to add to the versatility of musical expression. Exactly as in other musical devices, they can have an effect directly upon you without your being conscious of the precise mathematics Involved- You don't need to bother. You can make Beethoven and Bach sound dreadfully mathematical if you want to analyze them on paper, and Grieg. Tchaikowaky and Schumann, too, not to mention Gershwin! Bet- ter just to listen and let nature take Its course, by ear.

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Vivaldi: The Seasons. I Musici; Felix Ayo, vl. Epic LC 3216. A very exciting performance of the four connected concertos -Spring. Summer, Au- tumn, Winter-that make up this now very popular work. I have never heard so much real musical drama made of it. There is no exaggeration. no lack of taste. just simply superb playing and a real, electric, super - Italian rendering of that freshness and almost revolutionary daring of harmony that the the ultimate achievement in music systems piece surely land for its first listeners, back In the 18th century. It's an odd commentary on our perceptions The new Ampex Console Music System offers the startling experience that we really can to a considerable extent of stereophonic sound on tape ... a complete two -speed, half-track hear music as it was once heard, we can ex- AM -speed record changer and perience the meaning of it in its original tape recorder ... -FM tuner ... three ... terms, in spite of the centuries of later devel- two amplifier -speaker systems - each the finest component of its kind, opment that are part of our experience now. superbly integrated in the most complete sound system obtainable. \1't. can, that is, if the performance helps us. -t dull, unsympathetic performance merely Separately, the stereophonic player -tape recorder is available in handsome makes music like this sound antiquated and feeble. It is antiquated, In such u situation. table -top or portable cases with matching amplifier-speaker systems. Hear an (Just try the Columbia recording with the Ampex Stereo System today ... you'll never be satisfied with less. Philadelphia Orchestra!) But an aware, alive playing can project the original high intensity, as though there had been no long centuries of "progress" since that day. That's what happens here. I might suggest, incidentally, that the shift from Angel to Epic seems to have done "I Musics" good. Don't ask me how; maybe it's a different recording technique. Whatever the reason, I like this group of a dozen -odd strings very much here and so will you.

AUDIO DECEMBER, 1956 Ampex Corporation 934 Charter Street, Redwood City, California Monaural Recorder from $379.50. For complete A series brochure write Dept. B -3033 www.americanradiohistory.com SPECIALTIES

Mozart: Fantasia in C Minor, K. 475; Sonatas =10, K. 330, -14, K. 457; 7 Rondo, K. 511. Wilhelm Backhaus, piano. London LL 1399

IIere is the solo aspect of London's contin- uing serles with this leading German pianist. I'm all for It. except in the case of the extraordinary C Minor Fantasia ; there, it seems to me, Backhnns lamentably misses the sense and the architectural lines of the memorable slow opening (and closing) section, one of the strangest, most revolutionary tonal prog- ressions in all Mozart. linking the distant, dissonant keys of C and F -sharp together. Backhaus is not the one to play his Mozart in n flippant or show-off fashion. It is serious. dedicated, respectful, on the whole a bit stiff, not so much in the technique (he has all of that) but in the conception. Still, you'll find it good listening and good Mozart, and the piano is London's usual full -toned best.

Folklore of the United States: Jack Tales. Told by Mrs. Maud Lang, Hot Springs, N. C. Libr. of Congr. AAFS L47 This Is not exactly a hi -fl record, but I wouldn't let that bother you. The tales on it are quite hair -rasing. Jack, in case you didn't know, Is the U.S. counterpart of that famous Jack who climbed up to Heaven (or somewhere) on a beanstalk. The American Jack does all sorts of things. and in some of the Jack Tales (lots of people tell them, and the tradition allows you free rein to add your own modern details. for realism -like Ford pickup trucks and the like) the hero is so humptuously American you'd hardly know he had British ancestry. Mrs. Long tells the more old- fash'oned versions, minus Ford. But her's are the real thing, from her own Ma and not out of any book. Makes a huge difference. These are potent, up- dated legends and if you're n psychiatrist you'll goggle at the easy -going symbolisms A that pop up at every phrase-the age -old theme of all humanity in folksy, local -yokel disguise. She's a good tale teller, Mrs. L., and you'd know in a moment that her stuff comes straight down the generations. It's ...Head of its class that good. The Golden Treasury of Irish Verse. Read by Padraic Cclum. Spoken Ats 706 This is one of the large new series one in every group that stands is literally launched There's out...that ny R'evlminster in this field. I'll be touching at the head of its class. Among moderate priced 3 -way sys- on more of them Inter. As you listen to this you'll renl'ze a solid tems, the SENIOR is the outstanding example of what superb truth -that the "stage Irish" and "stage Scot- audio engineering can achieve. tish" accents we know from a million and one Each component of the SENIOR has passed the most rigid jokes and ploys and films, aren't quite the real thing: they're doctored, both to exaggerate tests and has earned its right to be part of this outstanding and at the sanie time to make them more system. The result is a thrilling sensation of sound which easily understood. Mr. Colum's Irish is the real thing. and his speech is a bit different from seems to surround you ... amazing in a system of this size. the kind you expect. Interesting. and it's a Treat yourself to the full -bodied lows of the powerful lovely language. the Irish -English. Colum rends many poems here, speaking in 12" woofer, the undistorted mid -range of the "reciprocating the old time way with a long. sing -song flare" horn speaker and the brilliant highs of the super - phrasing. Good for Irish verse, no doubt about tweeter, all kept in perfect balance by the Acoustic Baton V it. though it isn't the thing that's popular now- 4408 adays on radio and TV. The poetry lends itself network with its "Presence" and "Brilliance" controls. T to it. There's new and old poetry and many of The SENIOR enclosure is a beautiful piece of furniture the poets' names are unfamiliar to most of us. but we can afford to take Mr. ('plum's word that will enhance any room. Rigid, completely braced con- on his own selection: his written introduction, struction and the finest acoustic principles of phase inver- on the album liner, helps a lot. Also note one complete spoken story. by and rear horn loading result in a 04.3 sion, direct radiation Colum himself, about a fellow named Mae - music and speech. itaaghlin you hear him pronounce smooth, natural reproduction of PowerCapacity: 30 Watts (wait'll that) who goes to the local Irish fair and ask to see and hear the sensational SENIOR Integrated Program Don't wait ... loses all his money, but fast. at your Hi -Fi center. A delightful experience is in store Dimensions: Recording is excellent, from modern tape. for you! 30"Hx21 yz "Wx15,4 "D Shipping Weight: 95 lbs. The Art of Ruth Draper, Vol. 1. Price: Mahogany $185.00 RCA Victor LM 1959. LOUDSPEAKERS, Inc., 80 So. Kensico Ave., White Plains, N. Y. Blond 188.50 UNIVERSITY If you want to be mesmerized, as the old phrase goes, just put this on your machine and let it play. Perhaps some old -timers will remember LISTEN sPIGlGCÌS Ruth Draper. the one -lady theatre, In her hey- akii/a4 e1, IstEttui day. Maybe others will have heard her recent shows in New York and elsewhere. Early or

64 AUDIO DECEMBER, 1956

www.americanradiohistory.com late, the Ruth Draper touch is that of genius. She is surely the greatest dramatic mono money loguist of this century, at least. or have fun. ..save The lady just talks. She writes her own plays, for herself, and the thing that amazes The SENIOR speaker system is the outstanding example of what is that they are full of people -dozens of superb audio engineering ran achieve ... it stands Out at the head them. By the most wonderfully timed breaks, of Its class. producing a thrilling sensation of sound that's amazing pauses, juggling of ideas, she simply creates in a system of this size. It uses the powerful 1,12W no-der for full - to the point bodied bays. the 4108 "reciprocating flare" horn speaker for un- the other people in your mind, distorted midrange. the 11F2m; Super- nceeter for brilliant highs where you forget entirely that this is merely and the N3 Acoustic Baton :t -nay nernnrk to keep then in perfect one person speaking. Fantastic! balance. Enclosure Is a beautiful piece of furniture embracing the Take her acidly humorous sketch, here, of finest principles of phase Inters inn. direct radiation and rear horn the high -society lady trying to do an Italian loading. Mahogany $1s -..uo. Blond $188.50. lesson in the midst of house -hold management and the telephone. After a half -hour of this, you are positively exhausted with the strain of that woman's hectic life and the dozens of people surrounding her -from husband to chil- dren, manicurist to portrait painter to social secretary. Enough. If you don't try this on your friends and relatives, not to mention yourself, you're nut=.

The Art of Paderewski. RCA Victor Camden CAL -310. Poor old l'aderewski, relegated to the low- priced line! A passing thought, for this once most famous of world pianists is treated BUILD THIS technically just as well on Camden as he might have been on RCA Victor Iced Seal as of old, and he can be had for less cash. Reflects no AMAZING more than the passage of tine, which robs every man of his fame, sooner or later. Anyone who remembers the great days of this artist will want to try him out here. But SPEAKER you must make sensible reservations. First, the recordings are hardly thundering hi -fl, though in places they have plenty of power. SYSTEM... Second, it's a fact that many of Pade- rewski's records were made late in life when his powers were already slipping. Do you remember the great debacle, when this gentle It's so simple! old man was hauled out for a nation -wide broadcast on the fanciest top -drawer scale, and could scarcely play at all, his old fingers missing notes pathetically? And the anti- The Se11 for climax when shortly afterwards a mammoth Madison Square larden Paderewski recital was called off, mercifully, because of Doctors' orders? He died soon afterwards, as I remember. Same of these recordings reflect the begin- senility, though I must say nings of that THE PSE STORY hastily that it's not more than n trace. "DO -IT- YOURSELF" KWIKITS - All you need is a free Thirdly, remember that l'aderewski is of evening, a "KwiKit," a screwdriver and you can assem- PSE- Progressive Speaker out of Expansion Plan (a concept an earlier generation of pianists, right KEN-I 2 the 19th century. His playing is utterly unlike ble your own version of the famous SENIOR. The first introduced by University) the steely power -stuff of today's younger men. kit is the best of its kind on the market today ... a truly is the most revolutionary de- At first you may think it sentimental and velopment in speaker history. meandering. It's not. really. And you'll notice fine piece of workmanship. a standard trick of many pianists of old, the Except for a simplified front frame design, the KEN -12 University speaker compo- habit of playing the bass notes n bit ahead is identical in acoustic design to the SENIOR speaker sys- nents, enclosures and networks of the melody on each beat, for a kind of tear - have been so uniquely designed tem. Finest grade 3/4" Birch used for all finishing sur- jerking effect. Old- fashioned. that it is possible to start an Ile was the world's greatest pianist, for a faces, 3/4" cabinet plywood used throughout. Kit con- low good while, and don't think that some of it excellent basic system at isn't to be heard on this record, which includes tains: all pre- machined and pre- shaped wood sections; cost, and add to it later -while a whole gamut of concert favorites, from glue; hardware; plastic wood; sandpaper; easy -to- follow enjoying immediate listening Beethoven to Couperin, plus even that arch- you like to build your own and save satisfaction. modern, Debussy. And Chopin, as a matter of instructions. If course. money then the KwiKit is made to order for you. PS -E makes it possible tobuild up to the MASTER (or any other KEN -12 KwiKit ;39.95 net. fine system) in successive, in- Saint- Soens: Le Carnival des Animaux. THE EN -12 ENCLOSURE is the same enclosure used in expensive steps, using the KEN - Franck: Psyché Symphonic Poem. 15 KwiKit and EN -15. - the famous SENIOR speaker system without the speaker L'Orch. Symph. de la Radiodiffusion components. This enclosure is perfect for those who For the complete, Belge, Andre. Telefunken LOX 66028 either have speakers or who intend to build toward the fascinating story of This Telefunken LP offers a juicy piece PSE please send by Cesar Franck and the original version of SENIOR in successive steps, via P -SE. for FREE illo.c- the familiar "Carnival of the Animals," for Mahogany $75.00 net. Blond $78.50 net. Unfinished $64.50 net. trated brochure. two pianos and small instrumental ensemble. The Franck piece is competently played and recorded but somehow it lacks the romantic University offers the largest selection of speakers and components to meet every size and budget requirement punch that can make this one of the loveliest works of the late -Romantic school. Sounds sort of hum -drum and old -fashioned here, and the dead acoustics, radio studio style, do not help. The "Animals" fare very well, however, after a so -so start. and this in spite of some relatively inept playing by the two pianists. 40 who conte perilously near to derailment in a TWEE MPS DIFIAXIALS NETWO.R couple of places. (But you and I had better be UNIVERS T i OuDSPEAKERS. INC , 80 SOUTH KENICO AVENUE. WHITE PLAINS. glad we don't have to play the fiendish scale passages, etc.!) The original scoring is nice- - the ,Ingle string bass, for instance, is a lot more elephantinely humorous by itself than LISTEN the whole battery of basses in the usual full - testiPee4 sols orch.stra version of the piece. 6

AU 10 DECEMBER, 1956 65

www.americanradiohistory.com The magic word in spea/rers! PATENT LICENSING ELECTROSTATIC rc. r,I.r :i -: is an old one. So far as it .,orodact of9 gars a lr in,a legality has never been ques- tioned. As the restriction was legal and the ampliti,r- were made and sold out- of JaAsZe/7 side the scope of the license the effect is precisely the same as if no license research whatever had been granted. "' Frequently however, the licensing of patents has been prostituted to practices in violation of the anti -trust laws. Such an instance occurred in the marketing am' hacked oft aa,orecedeated of "dry ice," where each invoiee of this product carried an endorsement, "The merchandise herein described is shipped upon the following conditions: that dry ice shall not be used except in dry ice cabinets or other containers or appara- tn, provided or approved by the llryIce rhoration of America and that dry ice cabinets or other containers or apparatus, provided or approved by the Dry Ice Corporation of America, shall he refrigerated or used only with Dry- Ice." III the decision of au infringement suit by the owner of these dry ice patents the Supreme Court said of such titmlations. -To permit the patent owner to derive its profit. not from the invention on which the law gives its monopoly, The JansZen Electrostatic speaker brings laboratory- perfect but sound into from your living room! Unlike paper -cone speakers, the Electrostatic transforms tmpatented supplies with which it electrical energy directly into sound, through four electrostatic radiators is used. is wholly without the scope of arranged to give 500- 30.000 cps. response at 120 degree dispersion. the patent monopoly. Each of these four radiators is actually a condenser -type unit with a virtually "1f a monopoly could be so expanded massless diaphragm stretched between the plates ...driven over its the owner of a patent for a product entire surface by variations in the electrostatic field. This diaphragm is so might conceivably monopolize the com- light, it acts like just a layer of air ... thereby giving a perfectly flat response, mrce in a Inte part of the unrelated free from breakup and resonances in the audible range. An additional materials used in its manufacture. The advantage of the JansZen Electrostatic is that its radiators remain unaffected owner of a patent for a machine might by changes in humidity and temperature , .. so stable and dependable secure are these radiators that we guarantee them for two full years! thereby a partial monopoly on the unpatented supplies consumed in its operation. The owner rrf a patent for n process might secure a partial monopoly on the unrelated material employed *Radiators guaranteed 2 years; Mahogany. in Balance of speaker guaranteed 1 Birch. Walnut it. The owner of a patent in suit might year. Based on a remarkable new and Utility conceivably secure an unlimited monop- principle in the transmission finishes available of sound. on request. oly for the supplies not only of solid carbon dioxide but also of the ice cream and other foods, as well as the cartons in which they were shipped. "The attempt to limit the licensee to JUnSZORØECMO$MflC the use of nupatented materials purchased front the licensor is comparable to the attempt of a patentee to fix the loadspe0e1 price at which the patented article may he resold. In both classes of cases courts Send for complete literature on the JansZen 1 -30 Electrostatic deny relief against those who disregard O' as well as the name of your nearest dealer! the limitations sought to be imposed Product of NESHAMINY ELECTRONIC CORP. Neshaminy, Pa. by the patentee beyond the legitimate Export Division: 25 Warren St., New York 7, N. Y. Cable: Simontrice, N. Y. scope of its monopoly. "'

66 AUDIO DECEMBER, 1956

www.americanradiohistory.com L cense vs. Assignment

Tn the decision long ago of an appeal I. the Federal Supreme Court, was sit forth clearly the distinction between the license and the assignment of a patent and this distinction has been scrupulously followed by the courts of the country since that time. "The patentee may assign his whole interest or any undivided part of it. But if he assigns a part, it must be an undivided portion of the entire interest of the patent, placing the assignee upon art equal footing with himself for the part assigned. Upon such an assignment the patentee and his assignees become joint owners of the whole interest secured by the patent according to the respective portions which the assignment creates. "The patentee may assign his exclu- Which pickup is best? The ESL, reports The sive rights within and throughout a After impartially testing nine- specified part of the United States and Audio League. upon such an assignment the assignee teen leading cartridges, this authoritative report may sue in his own name for an infringe- concludes: ment of his rights. But in order to enable him to sue the assignment must "...The ESL Professional and Concert Series cartridges are by undoubtedly convey to him an entire and far the finest phonograph reproducing instruments we have heard." unqualified monopoly which the patentee held in the territory specified-ex - "In A -B comparisons with its closest competitors, even persons who cluding the patentee as well as others. had never previously been exposed to high fidelity reproduction were struck "For it was obviously not the inten- by the superior definition of the ESL." tion of the legislature to permit sev- "For sheer naturalness and undistorted ease, the ESL has no peer."* eral monopolies to be made out of one and divided among several different Give the best for Christmas: give the ESL. Your own ears and persons within the same limits. records deserve this superlative electrodynamic cartridge, too. "Such a division would inevitably lead Join the professionals- switch to ESL. Free information to fraudulent impositions upon persons upon request. who desired to purchase the use of the improvements and would subject a party who, under a mistake as to his rights, FOR L I S T E N I N G AT I T S BEST used the invention without authority, to be harassed by a multiplicity of suits instead of one and to successive recoveries Electro -Sonic Laboratories, Inc. of damages by different persons of the Dept. A ; 5 -5 4 Thirty -sixth Street Long Island City 6, N.Y. patent right in the same place. "Unquestionably a contract for the purchase of any portion of a patent right may be good between the Report. parties *Authorized quotation No. ç4. Please consult The Audio League as a license and enforced as such in the Vol. t, No. 6 -7 (March -April 195 5) for the complete technical and courts of justice. But the legal right subjective report. Additional information In Vol. i. Nos. to tr 12. Y. Subscription: t a issues $4, front P. 0. Boo 262, Mr. Vernon. N. in t he monopoly remains in the patentee and he alone can maintain an action against a third party who commits an infringement upon it. "s

4 General Talking Picture Corp. v. Western Electric Co., 305 U. S. 124, November 21, 1938 5 t'arbice Corporation v. American Pat- ents Development Corp., 283 U. S. 27, March 9, 1931 s Gayler v. Wilder, 51 U. S. 477, page 494. December, 1850

AUDIO DECEMBER, 1956 67

www.americanradiohistory.com NEW PRODUCTS

British -Made Tape Splicer. Suitable for movable front cover for protection of the Improved Leader Tape. A special anti- both mending broken tapes and for editing front panel. Noise measurements of dif- static coating and greatly increased purposes, the new BIB splicer comes ferent frequencies are measured in terms strength are among the features of the mounted on a flocked base, or it can be of their interfering effects on speech as new Scotch brand plastic leader and tim- mounted directly on any tape deck. The heard by the human ear. The dynamic ing tape No. 43 -P, recently introduced by body of the splicer, which is made of characteristics of the meter are such that Minnesota Mining and Manufacturing Co., nickel -plated brass, has two pivoted its response approximates the speed of ap- 900 Fauquier St., St. Paul 6, Minn. The clamps which lock into position to hold preciation of sounds by the ear. Weight- anti -static coating is said to reduce noise tape sections firmly in the splicing chan- ing circuits which simulate the action of the ear are also incorporated between the "Noise Input" and the indicating meter. Three weighting circuits are available for measurement of acoustic sound levels. Additional data can be obtained from The Raven Co., 530 West Mt. Pleasant Ave., Livingston, N. .1. D -3

Tape Storage Container. Stor-A -Tape is an integrated storage and shipping container for recorded tape, recently introduced by Concertapes, Inc., 522 Green Bay Road, Winnetka, Ill. Made of tough, high - impact plastic material, Stor-A -Tape is equipped with a center pin which sus- pends the tape inside the container. An- other patented feature prevents the con- nel. Both vertical and diagonal mitres are provided for either editing or mending. Horizontal mitres are also provided for use in trimming off surplus mending tape. A razor -type cutter is provided, which fits conveniently under the splicer body. Com- as the tape passes over the playback head. plete information may be obtained from while the increased strength -50 per cent Brcona Corporation, 551 Fifth Ave., New greater than the company's previous paper York 17, N. Y. D -1 leader tape- reduces possibility of break- age. A new marking system also has been Spillproof Tape Reel. The Irish "No- provided for more convenient use in tim- Spill" reel recently announced by ORRadlo ing. For use by professionals there are Industries, Inc., Opelika, Ala., is a new indicator arrows every 15 inches, while convenience for tape recorder users which for pros and amateurs alike there are eliminates the messy tangle of tape that "Scotch" plaid markers at 7% -inch inter- frequently plagues the average fan. The vals. The tape can be labeled with either reel utilizes two notches molded into each pencil or ball -point pen. D-8 of its flanges. As shown in the illustra- Ronette Microphone. Called the Rono- mike, a new semi -directional microphone now being delivered by Ronette Acousti- cal Corp., 135 Front St.. New York City, N. Y., is a high -impedance instrument with output of -55.4 db. Response is vir- tamper from rolling and permits neat tually peak -free from 30 to 10,000 cps, placement side -by -side on a library shelf. according to the manufacturer. The Rono- One large self- adhesive front label and mike is cased in a slim die -cast housing two edge labels, with spaces for tilting which is chrome plated. Modern, conveni- and cataloging, are provided with each ent shape and excellent performing char- Stor -A -Tape. Replacement labels are avail- acteristics make it ideal for use with tape able at nominal cost. Of special interest recorders, public- address systems, and in to tape correspondents is the fact that ham shacks. tapes can be shipped easily in Store -A- D -7 Tape containers without additional packing. D-4 Stereo Record -Playback Head. Devel- oped to meet the need for a low -cost high - quality stereo magnetic head. the TLD in -line unit can be compensated for flat Printed Circuit Hit. Intended for accur- response between 30 and 10,000 cps at 7.5 ate and simplified production of engineer- ins. It is compact and will provide long ing models or prototypes of printed -cir- wear with negligible oxide accumulation, cuit parts, this model maker's kit features provides excellent rejection of surround- tion, a rubber band is slipped over the a newly- developed drawing pen which ob- notches, holding the tape securely in place viates the use of paints, tape, photo- sensi- on the reel. The No -Spill reel also offers live coatings, negatives, etc. A completely easier access to the threading eye. An ad- etched circuit, ready for assembly, may be ditional feature is 28 square inches of indexing space on the four large flange areas. All Irish brand recording tape on 7 -in. reels is now being delivered on the No -Spill reel without extra cost. D-2 Noise Measuring Set. Designed primarily to measure noise over telephone circuits, the Daven Type 34 -B Noise Meas- uring Set can also measure acoustic sound levels, function as a transmission measuring set, and as a high -gain calibrated amplifier for audio frequency measurements. It is a portable, battery- operated instrument entirely self -contained in a metal carrying case provided with a re-

had in about 30 minutes. The kit is composed of the drawing pen and etchant resist ink, etching powder, a drawing guide, ing fields, and is highly uniform in fre- 10 copper -laminated Bakelite sheets, 10 quency and amplitude response. The head popular tube sockets and detailed instruc- features precision ground and lapped gap, tions for use. The entire kit is self -con- balanced electric and magnetic structure, tained in its etching tray and cover. Ma- high output, and precise colmnear align- terials supplied are sufficient for producing ment. Detailed dimensional drawings, at least a dozen circuits. Full information specifications, and prices will be furn- is obtainable from Photocircults Corpora- ished to manufacturers, distributors, and tion, Glen Cove, N. Y. D -5 dealers upon request. D-S

68 AUDIO DECEMBER, 1956

www.americanradiohistory.com Zlipsch Corner Speaker System. Known as the Shorthorn Model T, the newest eaker enclosure designed by Paul W. ltlplipech is built to dimensions which permits its use as a base for a table model television receiver. Frequency range of the Model T is slightly greater than that There's a prestige and thrill in of the Shorthorn Model S. Extending from below 40 cps, its range extends to above owning a Rondine! But remember too - you purchase a Rondine with peace of mind .. . assured the one shipped to you performs like the one at your dealer ... assured it will be quiet for keeps! Admire its colorful styling ... then look it over closely. Lift the turntable free of the well, and listen for the "pop" that tells you here is the ultimate in machining and self -lubrication for lifelong balanced rotation. 22,000 cps, with substantial efficiency from 45 to 16,000 cps. While it achieves Its Underneath is a motor so smooth maximum range when used in room corners, the Model T has a built -in corner soundless not find which permits it to be used in any part .. ... you'll of the room with slight sacrifice In the bass response. It is equipped with casters its equal in other turntables ! as a convenience for those who may wish move it from one location to another. Fort further information, write Kllpsch and Associates, Hope, Ark. D -9 Improved Reotifler Tube. Latest to be released in the new series of Amperes 'preferred' tubes for audio applications is the GZ34 rectifier, a heater -type tube designed to replace, without circuit changes, such rectifiers as the 5U4, 5V4, etc. It is equipped with a standard octal base and a 5 -volt heater which draws 1.9 amps. TURNTABLE

best of al! ... 'here's a Fondine for cr g bvedget.'

Rondine Ir. -2 -Speed ..$59.95

Rondine -3 -Speed .. . $84.95 Rondine Deluxe -J -Speed hysteresis synchronous motor $129.95 141,04 higher ;cast of Roe /ace

See your dealer. Write for Catalog and FREE strobe disc Output capacity is 250 ma, characterized R -O -KUT COMPANY, INC. by low output impedance. Other features of the GZ34 include excellent voltage 38 -01 Queens Blvd., Long Island City 1, N. Y. regulation, exceptional linearity in non - EXPORT: Morhan Exporting Corp.. 458 Broadway. N. Y. 13, N. Y. class -A power stages due . to lowered power supply impedance, and reduced CANADA: Atlas Radio Corp., 50 Wingold Ave., Toronto 10. Ontario ripple. Detailed data sheets are obtainable from Special Purpose Tube Division, Am- perex Electronic Corp., 230 Duffy Ave., background walnut Weldwood Hicksville, N. Y. D -10

AU NO DECEMBER, 1956 69

www.americanradiohistory.com Detachable -Flange Reels. To meet the ment, Stancil- Hoffman Corporation, 921 N. demand for a quick loading film reel for llighland Ave., Hollywood 38, Calif., has magnetic recorders, projectors, laboratory announced detachable -flange reels for 16 -, processing equipment and editing equip- 17.5- and 35 -mm film. The 1200 -ft. reel has a removable flange which allows the raw stock to slip over the reel, after which the flange is secured in place by a half turn to a locking position. The reel is made of aluminum so that magnetic film can be handled safely. Further information will be mailed on request. D -11 Knight Enclosures and Enclosure Sits. The new Knight speaker enclosures, in kit and completed form, have been announced as additions to the Knight line of high - fidelity equipment by Allied Radio Corpo- ration, 100 N. Western Ave., Chicago 80, Ill. Designed essentially for the low -cost Iti -fi system, the units introduced include one for corner placement to afford extended bass response, and another of conventional bass -reflex design. Each enclosure is highly flexible and can be used with a 12- or 15 -in. speaker for single, two -way or three -way systems. Both cabinets are constructed of % -in. plywood

with mahogany veneer. Highly attractive woven maroon plastic grille cloth is included. Builders' kits include all parts, YOUR INVITATION screw's, glue and step -by -step instructions for quick, easy assembly. Unfinished kits are smoothly sanded, ready for finishing. TO JOIN THE Full details will be mailed on request. D -1R STEREOPHONIC MUSIC SOCIETY NEW LITERATURE

Heath Company, 305 Territorial Road, Benton Harbor, Mich., now has available Here's the most exciting news since the "Heathkits for 1957" catalog, a 55- page hook which lists a complete line of HERE ARE A FEW you first discovered the listening pleasures high fidelity equipment, amateur radio gear, and service test instruments in kit MEMBERSHIP BENEFITS of recorded tape) form. Among kits listed for the first time is the new Heath "Legato" speaker sys- 20% SAVINGS ON tem which uses Altec Lansing drivers. AT LAST ... you can stop wearisome shopping STEREOPHONIC TAPE Other new items include an oscilloscope, RCA. HMV. Omega, Hi. Fidelity, Li tours hunting for the recorded tapes you want. a voltage calibrator, voltmeter, vibrator ingston, AV, Concert Hall. power supply, and CW transmitter. Copy The Stereophonic Music Society has been of the catalog will be mailed free upon 20% SAVINGS request. D -13 ON MONAURAL TAPE created to serve the needs of every music lover Complete listings in "Harrison Cata- ORRadio Industries, Inc., Opelika, Ala., logue of Recorded Tapes" or "Tape who appreciates the true fidelity and deserves high commendation for the ef- Reel." You receive a copy of one upon fectiveness of a small pocket -size booklet receipt of membership application.) convenience of this ultimate music medium. recently introduced under the title, "The 7 Old -Fashioned Villains of Tape Record- UP TO 50% SAVINGS This unique plan offers you one central source ing and How They Were Foiled." Cartoon ON RECORDING TAPE for every fine recorded tape on the market, illustrations are combined with interest- All lint grade, professional quality, ing text to stress the excellence of the recording tape' añd- through its large volume purchases cotnpany's Irish brand Ferro -Sheen recording tape. The back cover is devoted to FREE HI -FI MUSIC -passes on tremendous savings to you! a chart which shows the playing time for MAGAZINE SUBSCRIPTION various tape lengths and recording speeds.

You get 1 year subscnplmn (regular This booklet is both enjoyable and in- salue 33.00) contains complete cover- MEMBERSHIP RATES formative. (let a copy. D -14 age of tape, records and FM, reviews, Your entire cost for participation in the Society Purchase articles, etc. Plan and all the privileges described for a period of Amplifier Corp. of America, 398 Broad- FREE CATALOGUE 6 Months $6.00 1 Full Year 59.00 way, New York 13, N. Y., describes and OF RECORDED TAPES illustrates the Magnemite serles of port- The Stereophonic Music Society opens the door to you able battery -operated spring -motor tape Complete -up -to -date tally distributed to the finest recorded tapes in the world -offered to you quarterly. recorders in a new 4 -page folder which as soon as it is made available by all labels -at prices will be mailed without charge. The bro- you can't beat anywhere. Send in this application blank NO MINIMUM PURCHASE chure describes features of 15 models, all today, and enjoy the benefits of membership immediately! REQUIREMENT of which were especially designed for Order as few or as many tapes you MEMBERSHIP APPLICATION FORM------field applications. A complete listing of wish. TO: STEREOPHONIC MUSIC SOCIETY. Inc performance characteristics permits easy 303 Grand Avenue, Palisades Park, N. I. reference and simplifies selection. The re- D 6 month corders' operating features are concisely GENTLEMEN: Please enroll me for a period as a member in the l year explained and complete technical specifi- Stereophonic Music Society. I understand that I am under no obligation to cations, as well as direct factory price, purchase any specified minimum of stereophonic, monaural or recording are included. D -15 tapes under the Society's discount purchase plan. As part of my membership I am entitled to a free one -year subscription to Hi -Fi Music Magazine, as well as the quarterly listings of all recorded stereophonic and monaural Heroes Enterprises, 369 Shurs Lane, tapes available. Philadelphia 28, Pa., has issued a new 24- Check enclosed herewith (payable to Stereo - My page booklet which presents a detailed O Money Order for O $9.00 phon Music Society, I study of the theory and operation of the NAME ...... Ultra -Linear Circuit. Included in the book- ADDRESS ZONE. CITY STATE let are the mathematical analysis of - MAKE OF TAPE RECORDER ... ultra -linear operation and a typical ultra Stereophonic Stacked Staggered Monaural linear amplifier design. Booklets are available at 25 cents per copy.

70 AUDIO DECEMBER, 1956

www.americanradiohistory.com LOUDSPEAKER don't buy any DESIGN true fidelity tape recorder t/'rom paye .:1) better prospeets of presenting true wide unless it's Stereophonic, range without this effective resonance. But it is still necessary to see that the has 3 speeds and sells for less than $200 amplifier feeding it is provided with the necessary characteristic. We really need to reorient our thinking, rather like changing over from tubes to transistors. Instead of thinking in terms of driving voltage it would he more convenient to think in terms of a driving current since the current has to be passed through all the various reactances in series with the actual load we want to feed, which is the resistance element. ...e It would seem that the best way to combine a low -frequency dynamic unit with a high -frequency electrostatic unit, this if this is desired, would be to use separate amplifier outputs for each, so the BELL necessary high damping factor can be used with the dynamic unit, and a low damping factor with the electrostatic unit. An alternative method would be to Model BT -76 STEREOPHONIC THE ONLY make the electrostatic unit very ineffi- ... cient by using a large series resistance 3 -SPEED TAPE RECORDER IN THE WORLD to feed it. WITH "PLUG -IN" STEREOPHONIC SOUND An Final Obit/dive The writer rather feels that the final Simply plug the cable (supplied) from the objective will be to make the radiating built -in pre-amplifier of the BT -76 into the surface area sufficiently large so that the electrostatic unit can handle frequen- phono plug of your Radio, TV or other cies right down to the bottom end of the amplifier. Nothing else is needed to have the audio spectrum successfully. Experi- incredible realism mental units have already been made of Stereophonic Sound... which will do this and it is probably and, at remarkably low cost. Better buy Bell. only a matter of time before production versions of a similar type appear on the MONAURAL TOO! The BT -76 is also a dual - track, 3- speed, fully market. Another interesting possibility arises equipped monaural recorder; engineered for high quality recording and from a method of matching that has playback of all monaural tapes. already been tried by Mr. Peter Walker. This consists of using a number of elec- IT'S COMPLETE -READY TO PLAY -ONLY $189.95* trostatic units arranged as the capacitor elements in an electrical delay line. If ENGINEERED FOR THE FUTURE! The knowledge that your Bell these elements are arranged as the faces tape recorder will provide you with Sound, as well as of a horn, and the energy fed in at the Stereophonic other throat, it may be possible to improve wantéd recorder features, puts you in the enviable position of not having the acoustic matching as well as the elec- one of the many "outdated" recorders on today's market. Better buy Bell. trical matching by this means. As the wave down the horn the walls air travels BELL DESIGNED stereophonic equipment also includes the 3 -DTG will be activated to build it up as shown in Fig. 4. This requires an electrical Amplifier and the 300 -D "Sound- Cabinet ". See and hear them at Depart- delay line where the physical displacement, High Fidelity and Camera Stores. Write for literature. Bell Sound ment between plates corresponds with Systems, Inc., (A Subsidiary of Thompson Products, Inc.,) 563 Marion the propagation velocity of sound. "uch Road, Columbus 7, Ohio. `Priced slightly higher west of Rockies. a unit would require a large number of units to satisfy requirements at both ends of the spectrum, but, with modern circuit methods, who knows, it may yet RX "World Renowned for the Best in Sound" prove feasible '

AL A° DECEMBER, 1956 71

www.americanradiohistory.com AUDAX TONE -ARM 0 NOW IN KIT FORM Anyone can assemble it in about 10 minutes - and save 50% ! Exactly duplicates Audax "Compass-Pivoted" transcription arm long recognized as top "blue chip". "Selector- Index" permits instant adjustment for any stylus pressure. Newly -designed cartridge housing permits all- important stylus -to- groove alignment at a glance. Accommodates ANY MAKE cartridge. KT -12 $14.55 NET; factory- assembled 0 $24.00 NET. UD' Edward itnall Canby KT -16 $17.55 NET: factory -assembled IHAD A NUMBER of incomplete $30.00 NET. projects on The fact that you can't accidentally hand when I skipped the country, last drop the stylus on the record removes a season, for a long vacation from audio. large hunk of potential danger. It floats Most of them, as usual, involved LISTENING simple down, slowly. Yes, one can still scrape the QUALITY trial of promising products by the you - point sidewise over the record surface, but is everything use- 'em system, plain ordinary household this isn't too likely since most sidewise Impartial Lab reports on the neu use, the sort of gruelling test that this swipes are combined with some sort of Audak Hi -Q7 magnetic car 1rrJge: department excella in. Time is of the es- accidental dropping action. In any case, sence in such A leading recording studio: things -lots of it. The longer my ESL was used all summer by people I use a product, the more intimately do I who didn't even know it was expensive- "Because readings showed an know its pros and cons total lack of dis- and the only limita- they had kids, too-and it survived the amazing tion to such a trial, aside from the roughage tortion, check tests were com- remarkably well, as did any rec- plete collapse of the hard -pressed product ords, which were lying repeated 3 times." about in scads. itself, is the inconvenient fact that maybe Only a minor bending of the stylus arm Consumer sheet: a new model is already out and, in "Good frequency and any testified to at least one side -swipe. But the case, readers want to know what happened, cartridge still plays. And so I'm all for transient response. at least within a couple of no high dogs' ages. the viscous arm. And, incidentally, the Practically So I simply extended my viscous frequency distortion. tests by the fluid is so thick that it won't pour deadly expedient of leaving selected equip- out by accident unless you leave your player Low intermodulation ment in the gentle hands dittortion." of various friends on its side for hours or overnight. Perfectly and with the renters who took over my safe to carry. Listening quality is house for a few months. That, as any Give credit to ESL, too. It's a very everything - and the new Audax Hi -Q7 housewife knows, is the ultimate field test. fancy item of merchandise and one of the has it to a degree not equalled by any other Well, my !tot water heater burnt out, my finest pickup cartridges available today. pickup. But - HEAR it yourself . . toaster is kaput, the screen door won't But in a light arm with fairly low needle there is no other way! Net $47.70 with close and the garbage disposer collapsed; pressure (it can take it) this cartridge has 1 Chromatic Diamond and a Sapphire. the water pump failed, the lawn mower so far proved quite stable and solid. I'd Other models as low as $20.70 Net. drags one aide of its roller and the wood- rate it -so far -as a pleasingly foolproof chucks ate my chrysanthemums. All in all, pickup. the house came through pretty well, I'm It gets itself out of the way easily, telling myself, though even my barometer, bends its point gracefully against the hanging unobtrusively on a perfectly safe withering scrape and comes up unscathed wall, pointed to "Hurricane" when I got and ready to play -so far. "So far" in- back and has since progressed downward cludes many months of my own playing to "very dry." Somebody must have (with much carrying of the turntable bopped it. hither and yon while the arm swings STYLUS-BALANCE But when I turned on the Hi -Fi System, crazily about, banging into this and that . . . lists really works . . ." Canby it sailed off without so much as a squawk obstruction) as well as a couple of months Stop deformation of record grooves! Only of protest. Pretty good. in the hands of the Phillistines, my rentees. Audax Stylus- Balance can give you the all - The same was true of another quality So the evidence is impressive. important certainty of correct stylus pres- system that got a somewhat less drastic As to tone quality, I haven't heard any- sure- ALWAYS. Precision -calibrated like workout in New York while I was gone. No thing yet that's noticeably better than trouble a at all. But, on the other hand, two ESL. Mind you, things have now got to pharmacist's balance. Works with any patched arm and cartridge. Gold Finish. Net $4.80 -up affairs I loaned out to friends, the point where all top quality pickups made out of assorted odd items I had lying really sound the same. (add 2 S e if shipped from N. Y.) They have to, after around, were both dead ducks when I got all, if they produce no distortion worth back, and loud were the laments. Cartridge mentioning. And so I'll split no hairs as LISTENING QUALITY trouble, plus a couple of elderly changers between ESL and a number of quality CUTTERS that got tired of changing. They do that, rivals. I'll just say that the ESL, like a few years. Flat to 14,000 cps. after others in its class, is so extremely good Distortion 0.6% at that it's virtually transparent to sound. 1000 cps. Fully mod- I. An Arm and Two Cartridges What you hear is the music, the recording, ulates groove with in- the speaker. The pickup's individual con- My two good systems -the ones that tribution to the sound quality is negligible, put of about 16 db worked respectively an ESL with 220 lines. Z's up -had Concert and in that very fact it approaches abso- cartridge and a Fairchild, magnetics lute to 300 ohms. Two of perfection. What more can you ask. related sorts, the moving -coil. The ESL One minor mechanical observation. The models: cartridge was H -5 Net $111.00 (and is) installed in a vis- ESL models made in the U.S.A. have side - cous- damped arm, and must com- pieces H -4 Net $75.00 I say the next to the diamond point that serve bination is excellent. My arm is that in- as buffers and protectors. They also serve triguing Japanese model, sent me from as excellent lint -catchers copy of $1.00, 22 -page, /957 and, like several FREE Japan, that is inspired by the Gray arm. other pickup cartridges, including GE and reference guide, "ELEC- (Did hear TRONIC PHONO FACTS" by I that it now calls itself the Audak, the ESL, will occasionally foul it- - Grace? That's straightforward honesty!) self up with lint to the point where the pioneer Maximilian Weil - at your Whether you use the or dealer, or u-rile us. Gray, the Grace, sound is affected -until you blow the stuff or somebody else's viscous -damped, I rec- loose or pick it off with your finger. Not ommend the principle to you as a real important, unless you're obtuse enough not AUD.%K COMPANY honey for delicate cartridges on long arms to notice what's the matter and decide the 500 Fifth Ave., dept. A, New York 36 that are to be used by careless souls. pickup is going bad and ought to be re- Fine audio- elertronie apparatus over 30 years Rentees, for instance. turned to the manufacturer! People have

72 AUDIO DECEMBER, 1956

www.americanradiohistory.com done dumber things than that, I assure and got with the usual variable -reluctance you. (And anyway, you shouldn't have lint types of magnetics. Top sound quality, but on your records... ) still a relatively low output. The transformer-filter that comes with Nevertheless, this is good. It's not easy the ESL is unexpectedly functional. The to get both quality and reasonable output transformer, of course, is required to boost out of the top -ranking moving -coil type of the very low voltage of the moving -coil cartridge and Fairchild has done nobly to type unit up to par for the average am- get enough to drive any amplifier at all, HIGH FIDELITY plifier. The filter is also an unexpectedly minus transformer. useful addition to take the edge off the The newest Fairchild, the 225, does extremely high frequencies, mostly super- better still and on the basis of this per- 71e Orygget foc Lem-! sonic sonal experience with the earlier model I'd It turns out, you see, that a really flat say that for all normal listening the cur- pickup response, 'way up in the tonal stra- rent Fairchild will perform for most people tosphere, is a two -edged sword. Many re- very nicely without transformer. So much cordings, non -too -perfect, produce assorted the better. But if you whomp up the vol- high supersonic hash that, if it is picked ume, play music super -hi -fi and blast your up, reacts most unpleasantly with the lower neighbors out of their seats, you'd better o a & audible frequencies to give a harsh, ugly get yourself a supercharger . . . I mean . sound. Intermodulation. Most cartridges a transformer. il .. are blissfully insensitive to the highest so well here. highs, supersonic, and all is 2. The Big Z. But these new moving -coil models, the HF155 ESL and, for another, the Fairchild, do a It 's just as well the JansZen people put fine job of reproducing the supersonic hash. Z name. that big in the middle of their I HI TUNER And so-the supersonic filter. ESL builds was beginning to get desperate, trying to FM -AM -FI into assembly, it directly the transformer remember how to spell it, and though the Here is quality FM (response ± 0.5 db, the whole thing mounted as a miniature Jensen speaker people probably weren't and improved AM, However, for many really good 20 to 20,000 cps) attachment. turning a hair, I was losing mine thanks both most perfectly realized for finest new recordings, minus hash, you can turn to telephone calls and questions in person a the filter off and this type of cartridge reception in a unit only 4" high -at that constantly wanted to know about Outstanding fea- then gives you every last bit of true sound Jensen when it was JansZen and JanaZen very reasonable price. tures : Sensitivity, FM -3 microvolts for that can be recorded on plastic. when it was Jensen... . "You mean the one with the big Z in 20 db of quieting; AM -5 microvolts for 1.5 volts output; separate RF stage Fairchild it," I now ask. Or vice versa. Anyhow, the JansZen electrostatic on FM and AM; discriminator with limiters; cathode follower with 2 1 haven't tried to make any sound dis- speaker has been operating in my home for dual tinction between the ESL and the Fair- some months now and, after all that time, outputs; AFC; flywheel tuning, FM child, two magnetics of similar principle. I am well enough used to it so that I can di -pole antenna, etc. If there are differences noticeable, they are say in all confidence, it's good. utterly minor as far as I am concerned. It's not that I notice it. I didn't really NEW HI -FI SOUND FOR TV! notice much when I first installed That is, other differences that crop up- change Now make your TV sound "come between recordings, between room- situa- it, as tweeter to my present AR -1 woofer. alive". Just plug the new RAULAND tions, between loudspeakers-are so very On casual acquaintance it sounded -well, TV55 Tuner into the unit above and like a tweeter. gave out with the enjoy TV sound through your hi -fi system. much greater, that the difference in pickup just It Exclusive with RAULAND. See it- sound is of inaudible importance. highs and the music was complete. Funny hear it soon. The Fairchild cartridges have been inch- feeling, after all the fuss that's been made ing up in output to the point where, though about electrostatics! of the low -output moving -coil type, they But the fact is that most people will can now be used directly in most amplifiers notice no immediate and stunning miracle. minus the extra transformer. Saves cash The electrostatic tweeter just goes to work, and is simpler. The newest moded Fair- faithfully and unobtrusively. Mine is still child has the highest output so far. I've working and nothing has burnt out or been using the next -to -last, the 220, for busted -yet. some time now, and I deliberately put it to The funny thing is this. Now, however, work without a transformer just to see for I hear the other tweeters, as speakers, and myself what it would do. I don 't like it. I hear them themselves, Well, the answer is borderline. Minus between me and the music. I'm aware of transformer, the Fairchild output is en- them as speaker -entities. The JansZen is tirely OR in some situations, perhaps not less in evidence to my ear. It's more trans- 20 -WATT HI -FI AMPLIFIER quite potent enough in others. But before parent. I'm hardly aware of it at all. Designed for those who appreciate the you take that in, remember a very im- Now that may seem anticlimactic. But finest in Hi -Fi reproduction -the very portant point. it happens to be exactly what the JanaZen Full 20 watts by rights. best for less. Features: 1t isn't the power output of your am- ought to do, by claims and It response, ± 0.5 db, 20 to at all; isn't the is transparent to sound, as in a similar output; plifier that counts here it 40,000 cps; 6 response curves (compen- wattage you have on hand. The input sensi- manner is the ESL cartridge I'm using for all record types); 5 inputs for tttity is what counts. That 's not so often with it. In this day of near -perfection in sation mentioned in the published specs and not audio equipment, there can be no greater complete hi -fi versatility; separate bass, nearly as well known a figure. compliment. treble controls; contour and volume To put it colloquially for those who may I haven't tried any of the other quality controls; variable damping control; not be clear on this point, the sensitivity electrostatic units yet, but I fully expect rumble filter, plus many other deluxe represents how hard your amplifier will you will find the same thing true of them. features. In compact cabinet, 4" high. jump for a given (input) kick in the pants. And indeed, at the New York High Fidel- Some older babies, though they may give ity Show, I listened to the Pickering ex- HANDSOME "SPACE- SAVER" DESIGN out with a whopping 50 watts under pro- perimental full -range electrostatic speaker RAULAND matching "Space- Saver" vocation, need plenty of that provocation system (not for sale) and experienced the units are decorator- styled in smart char- high input kick -in order to do so. same odd feeling of anticlimax -I simply coal black with marbleized gold finish, -n control panels in soft brushed brass. No Others though rated at, say, a mere 10 heard a good record, straight through the cabinets required -fit beautifully any- watts, may bust a 10 -watt blood vessel for speaker. 1 scarcely seemed to notice the where. (Extension shafts available for half as much input kick. speaker as such. behind -panel mount.) On my somewhat elderly and averagely These electrostatic people are going to sensitive 20 -watt amplifier, a quality piece have a time selling their hi -L It doesn't Hear these of equipment, the Fairchild 220A without make enough noise on its own. But, speak- RAULAND Hi-Fi transformer gave with enough kick to drive ing seriously, I am convinced that the elec- units at your the power stage to a reasonably loud room trostatic speaker has already sounded the dealer's, or write volume, plenty for my listening. Not death knell for the raucous, ear -splitting for full details enough, however, to reach maximum. And kind of " hi-fi" that has been so popular when I came to do some recording work I these last few years. RAULAND -BORG CORPORATION found I didn't have the wallop I needed, As long as speakers continued to have 3515 W. Addison St., Dept. C, Chicago 18, III.

AU DIO DECEMBER, 1956 73

www.americanradiohistory.com audible, measurable individuality, hi -fi was shows, which can do a lot of harm -not to really a matter of taste. Pick your speaker the audience, which at worst is merely dis- and choose your own brand of Iii -fi sound. appointed or misinformed, but to the pro- Speakers have long been far behind, in- moters who, we can assunse, are hoping to evitably, in the race for low distortion. sell hi -fi, not to sell it down the river. I Couldn't be helped. But now, with electro- think two things ought to be better under- statics, the high end at least is beginning stood. really to catch up. The electrostatic (und, First, I don't feel it's really necessary I gather, one or two other new types of any more to point out to the public that speaker, such as the ribbon tweeter) is in- hi -fi reproduction now comes close to a herently and by principle "flatter" in its mechanically exact imitation of "live" response than conventional drivers. True sound. Second, I am very sure that it is sound transparency, where all speakers will dangerous and misleading to suggest that sound alike, is not far off in the higher a literal comparison be made between tonal range, and I'll be only too happy sound recorded and reproduced in n hall when it arrives. and the sanie sound produced there directly by living musicians. 3. The Ultimate Transparency? As to the first point, I'll admit that there Report from the still is gold to be mined out of Use idea of Indeed, I can't help thinking, what else perfect sound reproduction. It is not yet LABORATORY is real hi -fi but complete sound transpar- taken for granted by the public, in spite of ency? What else have we been working to- generations of power -packed advertising on Vie Audio ,Ceague Report* wards, all these fine years, the subject. Maybe the ads aren 't as potent Now we have, at least on tape, recording Lg. $ as they claim. All I know is, sound repro- Acoustic Output at )0 CPS that comes close to technical sound trans- duction was claimed indistinguishable from parency, thanks especially to fine mikes, "live" sound 'way back in the acoustical now almost sound -transparent. Records are period. Old Tom Edison himself put on AR-1W not too far behind but it's possible they'll dramatic demonstrations that pitted living The League's ref soon be our weakest link, hi -fi or uo. Am- erence standard singers against their own recordings, and plifiers, the all- electric part of the chain, everybody seemed to think there wasn't are 'way out ahead. No measurable dis- any difference at all. Yet people atilt won 't tortion. believe it. It takes continued p,rsuasion, And other points, we now 15 speaker p at transducer and the idea still has fascination. It'll system A have virtually transparent pickups. Our draw crowds, and sell hi -fi. speakers are approaching transparency Yet the fact is that quality sound repro- through many different paths of develop - duction ran be taken for granted today and ment. by all rights should. I, for one, stn really 12" speaker V We've eliminated one of the biggest ste m 1 not at all surprised when I hear reproduced headaches in one part of the reproduction sound that, on grounds of distortion, is in chain -record equalization. Now, we no effect as good as the original, a trite fac- longer can "hear" equalization. It, too, simile for the entire length of the reproduc- has become transparent thanks to the now tion chain. 15" speaker r nearly system Z universal RIAA curve. On the other hand, I am shocked on those What more is left? Not much! We'1) just occasions when I hear less than perfection, have to pay more attention in the future to when there is audible distortion in a public the original sound, the living source of all showing of hi -fi, or when there is hiss, Iii -fi we've ever had. Speech and music. Vol. No. 9, Oct., '55. Authorized Quotation #28. the rumble, sputter, or worst of all, bum. Dis- For the complete technical and subjective report on That'll be just fine with me. I always tortion in all its forms is now inexcusable he AR -1 consult Vol. I No. 11, The Audio t was a music critic. Report, Pleosontville, N Y. in public except in minute quantities, mostly in the still -weakest -link, the loud- 4. Hi -Fi versus the Real Thing speaker end of the system. Report from the As I go to press, so to speak, I've just In other words, the technical perfection had to mitts another in the current series of of reproduced sound that is so loudly bal- WORLD OF MUSIC High Fidelity Concerts, those big, public lyhooed in the publicity for the hi -fi com- demonstrations before a paying audience parison shows should be taken for granted. where the best in hi-fi equipment is dra- Anything less is a technical disgrace. matically pitted against the "real thing," Yes, I know, the gremlins are always the old original, the actual, unrecorded, around. Things just do go wrong, people living sound. This one involved the entire make miscalculations, do silly things with Hartford (Conn.) Symphony and should connections and go around losing ports at have been a honey -if everything worked the crucial moment. Gray hairs are bound out as promised. FM radio got in, too, to start sprouting in anyone who brashly rounding out the hi -fi picture. gets himself involved in a publie hi -fi This kind of supreme test makes for a demonstration. I commiserate. But never- good show stunt. The crowds are likely to theless, I must state that these risks are rush to it, and you drag out not only the part of the deal. Gremlins are not allowed hi -fi bugs but, if you're good, a fair num- for its the specs, nor in the advertising. The show must on, The Aeolian- Skinner Orga.t Co. uses an AR ber of music -lovers as well. come to see how go and as far as the mech anical woofer (with a Janszen electrostatic tweeter) their art stands up to hi -fi's best, and even and electrical elements are concerned it line to be perfect, and is in their sound Joseph S. Whiteford, vice some professional musicians. there to watch that studio. Or nt least as pres., writes us: the torture of their confreres! So they that. perfect as Ivory soap. confidently expect, anyhow. Perfect, except, of course, for certain "Your AR.IW speaker has been of Whether the living music and the fleshly Other Factors, not even concerned with the inestimable value in the production of our re- musicians get murdered or not depends on equipment. My second point. cording series 'The King of Instruments'. No some very tricky and, indeed, crucial fac- Those Other Factors, not usually men- 1 have ever heard does justice to other system tors. It's more likely, alas, that the hi -fl tioned in the prospectus, not touched upon the intent of our recordings. Your speaker, with will get the ncoisticnl axe, right in front in the advertising, sometimes not even its even boss line and lack of distortion, has so of the paying customers. That's what can known to the operators, are so big they closely approached 'the truth' that it validates hurt! There is so much to understand, so actually dominate the entire hi -fi- versus -live itself immediately to those who ore concerned much to get dono in these tricky shows, program. They are "it." It is they, the with musical values." that to undertake one of them is to risk strictly non -electric, non -equipment aspects, AR speaker systems (2 -way, or woof- your living soul. I hereby warn anybody that will make or break your show. er-only) are priced from $132 to $185. Cabinet who plans such a venture to wntclu not The invited and /or paying public comes size 14" x 119e" x 25 "; suggested driving power only his Ps and Qs but to take off a year in droves to these hi -fi "concerts" to hear 30 watts or more. Illustrated brochure on or so, first, to learn just what he's up what they expect to he equipment perfec- request. against. A big proposition. tion. \flint they actually hear is very I'd like to suggest right here that there largely a juggling of the local acoustics- ACOUSTIC RESEARCH, INC. is a dangerously wrong emphasis going well juggled for a good comparison. or S4Thorndike St., Cambridge 41, Mass around these days in connection with such badly juggled for a ghastly flop. The sheer

74 AUDIO DECEMBER, 1956

www.americanradiohistory.com quality of the assembled equipment, alas, out with as near to an exact acoustical Las a relatively small role in this drama. match in the two sounds as possible. If That 's the horrid rub. you understand what you're up against, If you have solved your acoustical night- you've won half the battle. mare- problems with skill, understanding Don 't mislead the public by ignoring and, maybe, good luck, you can get away these factors. You'll do your explaining at with all sorts of semi -distortion, you can the actual Hi -Fi Concert, or maybe you use surprisingly mediocre equipment, and won 't explain at all. But in your advance still the audience will be thrilled. But if publicity, don't give a wrong impression. you have not faced up to the acoustical Don 't tell the prospective audience in so problems, if you dodge the issue or flub it, many words, that your hi -fi equipment will you may have the best equipment in the offer a LITERAL reproduction "identical world and the results will be dreadful. Who, with the living music as recorded on the what, gets the blame, Natch, the hi -fi very same stage." 2 sellers and their equipment. Lousy equip- Not, at least, unless thanks to extreme The AR -1 acoustic suspension' speaker ment, says the audience, and how very, wizardry, incredible intuition, or darned system is now widely recognized as reproducing very wrong they can be! Bad thing. good luck, you actually have been able to Frankly, I am delighted when a relatively make a recording on your concert hall stage the cleanest, most extended, and most uniform mediocre batch of equipment, thanks to a that will play back without acoustical com- bass at the present state of the art. It is em- good acoustical set -up, does better in the plications, for a relatively perfect com- ployed as a reference testing standard, as a way of realism than it has any technical parison. It's impossible of course, but it right to. It happens often enough and not has been done. It can be done -sometimes. broadcast and recording studio monitor, as an only in concert halls. Many a so -so home If so, you're entitled to tell your public acoustical laboratory test instrument, and in hi -fi system can sound out with incredible what's in store for them-you can claim realism because of ideal acoustical set -up. a REMARKABLE similarity, a fantastic- thousands of music lovers' homes. Even little peanut radios and miniature ally ingenious illusion, you can imply, cor- The AR -2, our second model, is a two -way portables can do it, on occasion. rectly, that your technicians have solved But on the other baud, I am deeply mountainous technical and acoustical prob- speaker system (10 in. acoustic suspension distressed, and so would you be, when I lems. Even if your show seems to make a woofer and newly developed tweeter assembly), know to be -fi and real see and hear equipment that I perfect match between hi the in a cabinet slightly smaller than that of the excellent maligned simply because it sounds thing, even if your orchestra can put punk in a poorly calculated acoustical down its instruments and the sound ap- AR -1 -131/2"x24 "x1l3/4". It is suitable for use situation. It happens at every hi -fi equip- parently goes on with never a break -don't with any high quality amplifier which supplies ment show, as we all know. (One reason mislead. In the name of constructive why I never try to judge sound quality at honesty and in your own self defense and 10 or more clean watts over the entire audio a hi -fi show.) And it can happen with a that of the industry, don't ever imply that range. vengeance in the trickier and more sensi- the two sounds, recorded and live, can be tive situation where reproduced sound is to identical merely because your hi -fi equip- be compared directly, AB, with living ment is 99.44 per cent perfect.. That is sound. In that comparison you simply ask simply not true, no matter how good your for the worst by pitting the natural, on -the- show is. spot, two -eared original against sound that And if things don 't go so well in your is reproduced through the acoustically un- first experiments, be sure you know it. natural medium of the loudspeaker, with I have beard enough acoustically faulty its one -eared, double-echoed reproduction. demonstrations to be well aware of how What's the general approach that's badly things can go. Too little experiment- safest, if you are bound and set to coming and too late. Be sure you have your pare your local symphony orchestra, string hall available well ahead of time, and your quartet, organ and what-not with the sound equipment and your orchestra too. Be sure, The price of the AR -2 in harawooa veneer of the same, reproduced hi -fit somehow, that you allow for the differences I'm not worried about the details, which between empty and full hall acoustics (al- is $96.00, compared to the AR -1's $185.00. will differ radically in every set -up, any- ways assuming you'll have a fine audience) Nevertheless we invite you to judge it directly, how. an easy calculation to make. Let's stick to principles. -not at your sound dealer's, against conventional Hatch, first and foremost, be sure that And keep working at the tricks, at mike your equipment is good, has enough power, placement, at loudspeaker placement, over bass -reflex or horn systems. The design sacri- dizzy enough versatility (for equalization - and over again, until you are and fices in the AR -2, comparatively small, have equalizing the live and the recorded sound) your musicians have practically worn out and that it works. Kill off the gremlins their instruments. This you'll have to ex- mainly to do with giving up some of the AR -1's before they 're born. And be sure to have pect, unless you're just plain incredibly performance in the nether low -frequency re- on as much quick- action stand -by equipment, lucky. Or unless, as I say, you have gions, performance which is most costly to come just in case the impossible happens and hand a wizard, a magician, who can set up everything goes up in smoke or you get his mikes and get the ideal recording the by. The AR -2 can radiate a clean, relatively full nothing but loud blats and squawks. I hate very first time. But don't count on that. signal at 30 cycles. to say so, but the impossible is quite Wizard or no, the reasonable odds of na- probable on these hectic occasions! Or you ture are all against it. Normal procedure The AR -2 speaker was designed as the should assume so, anyhow. is to try, try, and try again, and that standard for medium -cost high fidelity systems. of work, Then, before you have even begun to means hours and hours and hours Our tests have shown it to be so far ahead of its complete your equipment set -up, begin to over and above that expended merely on work overtime on DOUBLE LIVENESS. assembling the necessary hi -fi equipment in price class that we think it will come to be Unless you are a sound wizard, you will the hall. regarded as such a standard within its first year. not be able to record your musicians and I'll continue this discussion in a later play them back in the same hall for a issue, and will hope that there'll still be a direct comparison with themselves. few brave souls around willing to stick You must immediately face the fact that necks out and try a "Hi -fi Concert," in the recording you have two livenesses living musicians, hi -fi systems and all. I added together, with no directionality (or don't doubt that there will be, for not only at b. -st a limited separation, as with stereo does hope spring eternal in the human recording), pitted against one, single live - breast, as somebody once said, and the next ness and infinite directionality in your live guy is always sure his big demonstration musi,. These are fundamental differences is going to be the ultimate, but it's a plain that can make the two sounds as utterly fact that the millions of people who buy unlike as you can imagine in your worst hi -fi are truly concerned with it, and they nightmares. And -almost always -the really do want to hear what happens when "real" music sounds better. The repro- hi -fi runs head -on into the Real Thing, right Literature, including complete performance duced sound, through no fault of the equip- in front of their own ears. They turn out in ment, is the sound that suffers. Fine thing! droves. specifications, available on request from Therefore, you must plan knowingly and They don't even know about double ACOUSTIC RESEARCH, INC. liveness, but you had better. experiment constructively, using every Cambridge 41, Mass. trick you can lay your hands on to come (To be Continued) 24 Thornlike St.,

AU 0 DECEMBER, 1956 75

www.americanradiohistory.com Assemble Your Own TRANSISTOR EASY STAGES FOR LtïLrilr7r 't (from page 471 HIGH- FIDELITY

grid bias: is SPEAKER HI this the normal cathode - SYSTEM -FI bias arrangement. The advantage of this is that the grid -bias voltage is dependent PERFECTIONISTS on the plate current, so that changes in plate current due to aging or other Another TANNOY speaker triumph effects cause a change in bias voltage The now world- famous TANNOY DUAI which tends to maintain the plate cur- CONCENTRIC speakers have established a rent at its original value, thus stabilizing standard of reproduction so high as to the operating point. embarrass those among the perfec- Guided by our knowledge the tionists who must use, or prefer to use. of tube multiple systems ... and, of course. cathode -bias circuit, let us examine the those whose budgets won't stretch in effects of placing a resistor in series every direction at the same time. They with the emitter of a transistor, as need be embarrassed no longer ! The shown in Fig. 2. We analyze this circuit new TANNOY Iz" Direct Radiator is It's Easy and Inexpensive their starting point. No single speaker as follows. can offer a better introduction to the The voltage at the base is set by the to "DO IT YOURSELF" realm of realism than this product of divider R,R so that the base voltage ASSEMBLE THE ELECTRO -VOICE English craftsmanship. is EMPIRE Low -Bov KD 5 SPEAKER The new TANNOY 15" L.F. unit and the R, CABINET. Kit contains everything new horn- loaded H.F. unit (both based VR, on the performance specification of the Vb +R; you need -precut panels and cleats, DUAL CONCENTRICS) follow -but not glue, screws, and easy -to -follow di- necessarily together -to bring the system As before, we can assume that the base - rections. It's yours for $51- as near perfection as human skill can to- emitter voltage drop is negligible, and Build your own, if you prefer. Buy devise. A specially designed cross-over the emitter voltage will be just the illustrated construction network ensures optimum performance book -$1.00 -get your materials from a two- speaker set -up until the R, from local suppliers. budget permits adding the final unit. ve= VR, The original u" Direct Radiator now vb= -4- Give your completed cabinet a furniture finish- cherry, cordovan achieves its remarkable best as a mid- The range speaker. Here indeed is perfection current in the emitter circuit is mahogany, walnut, golden oak, in easy stages! Ve V R, fruitwood or ebony. Finishing kits, $5. t0 R3 RI (RI +R¢) Improve Your Speaker System The current flowing in the collector will One Economical Step at a Time he FOLLOW THE SENSIBLE ELECTRO -VOICE BUILDING so I1 +11er BLOCK PLAN. Start with an 15 INCH and since ß is large compared to one, Electro -Voice SP15B co- LOW FREQUENCY changes in ß will have only a slight effect axial full -range speaker. UNIT Just $43 net. on tic. Compare this to the circuit of Fig. For those silky highs, add 1, where is was directly proportional to E -V Model T35B VHF R. driver A'P67 level control The value R4 can be and Model X36 crossover. of now chosen For added mid -range re- for the best operating point: sponse, install Model T10A HF driver with Model AT37 HIGH FREQUENCY (V R4-1(17-1 -ve)' level control and Model HORN- LOADED i 2 ie X825 crossover. UNIT so that Complete your three -way speaker system by adding (V = (V +ve), these components to your vc=V 2 v) basic speaker and thrill to a magnificent 3 -way system. Since changes in 13 cannot appreciably Difference 12 INCH affect the collector current, these changes Hear the DIRECT SEE YOUR ELECTRO -VOICE must "reflect back" to change the base DEALER TODAY. Dial the RADIATOR 1( current which will be E -V Speaker SYSTEMS SELECTOR and hear the is ib improvement as you switch from a single speaker to a multi -speaker However, changes in ib have a negligible system. effect on the operation of this circuit. Write for Bolbtin 211 A612 `TAN N OY ` This will be true for values of R, and R, such that the current i flowing in the divider R,R is large compared to CL(JLf7racL Practitioners in Sound the base current ib drawn by the transis- ELECTRO- VOICE, INC. BUCHANAN, MICHIGAN Tanner (America) Ltd., 38 Pearl Sheet. New York s, tor. That is to say that N.Y., U.S.A. Tsnnoy (Canada) Ltd., 36 Welhnvon Canadas E -V of Canada Ltd. 1808 Avenue Road, Street East, Toronto I Ontario Canada. Toronto. Ontario V Export: 13 East 40th Street. New York 18, U.S.A. / >r6 Cables: ARLAD Circle 76A R t +R t Circle 76B

76 AUDIO DECEMBER, 1956

www.americanradiohistory.com Unless this is true, changes in ib will cause vb to change, and the circuit will be less stable. Since the operating point is essentially independent of 0, this circuit will be insensitive to transistor replacement or temperature change, inso- far as bias conditions are concerned. A Correct Example Using the improved circuit of Fig. 2, let us design an amplifier with a CK722 transistor. Select ie = 0.5 ma, with a supply voltage of 10 volts. The value of v= vb should be twenty to thirty percent of V, say 3 volts. Now calculate

R = e =6K, c 1 ve) R4 =2(Vti -7000, preamplifier with cabinet $168° e

vo = (V +ve) =6.5 volts.

Since a typical value of 0 for CK722's is 15, we will have

ib = ±ma, or 33 p.a. =i sllphtly hgher west of the Mississippi For good stability, the current is flowing through R, and R, should be several large ib, 200 times as as or about pa. write for literature Then ma rani company 44 -15 Vernon Boulevard, Long Island City 1, N. Y. R,= - 15,000, 200 let and - q R, = V 30,000. 233 pa Note that since the transistor input impedance is only about 1000 ohms, the signal power lost in the divider will be c uí! negligible. For the circuit values calculated above, the measurements in Table 2 were recorded. The transistors were the same ones used in Table I. Note the considerable improvement in changes in TAPE RECORDERS

TABLE 11 AND

le, ma. v., volts 10 0.46 6.8 TAPE RECORDING 13 0.47 6.6 15 0.49 6.5 18 0.50 6.4 Rv 24 0.54 6.2 31 0.55 6.1 Harold D. Weiler io and ve with respect to 0, compared Author of with those of Table 1. The stability could "High Fidelity Simplified" be further improved by reducing the values of R, and R, so that i, is even larger compared to ib. The first complete book for the home recordist. Tells why, how, It is apparent from comparing Tables and what in easily understood language too technical, yet 1 and 2 that no product incorporating -not technically room acoustics, micro- transistors could be mass produced using accurate. Covers sound, microphone techniques, and splicing, sound the circuit of Fig. 1. Each transistor phones, editing maintenance, adding sound would require a different value of R, effects and how to make them, and movies. to set the collector current to the proper to slides and home value, and even then, ie would drift con- .. $2 95 siderably with age and temperature Board Cover .. $3.95 Paper Cover changes. Only a stabilized circuit such Use Book Order card on insert at back of this issue as that of Fig. 2 would be practical.

AUDIO DECEMBER, 1956 77

www.americanradiohistory.com Referring again to Fig. 2, C, must be large enough to bypass the transistor ' / / emitter resistance much needed auclifory meun.t o/learn- at the lowest fre- a t quency of interest. For audio fre- iurj houe lo use your fane recorder properly. quencies, its value should be at least 50 µf, but for high fidelity applications, 500 Ad will be required. Use low -voltage ,. electrolytics for this purpose. The value of C, should be 2 to 10 pf for audio frequencies, unless the preceding stage Ava fable on one 12" has a very high output impedance. In LP High Fidelity record. Prepared by the engineer- this case a somewhat lower value will ing staff of Crest Records suffice. The value of C, will be deter- under the supervision of mined by the load impedance. To couple Mr. Hal Michael. Nar- into another transistor at audio fre- rated by Dr. Miller Mc- Ciintock of Sound Book quencies, use 2 to 10 pf. If a vacuum Press. tube circuit follows, a .05 µf capacitor The record consists of will do the trick. examples of both the cor- Remember, the tremendous advan- rect and incorrect ways of tages of making tape recordings transistors can be realized only done with full explana- if proper circuits are used. The type of tion. circuit described here has been operating A must for the tape re- for over six months in a high fidelity corder enthusiast. preamplifier and control system. It is completely trouble free, and provides . sound quality equal to or better than Now available at your dealer comparable vacuum tube circuits. or send $4.98 direct to

Please no COD Records will be sent prepaid. CRCSt RECORDS, INC. MULTIPLE TAPE 220 Broadway, Huntington Station Y. 25, N. (From. page 36)

for spot checking. The foregoing is included because the Magnecorder PT -6 is still widely in use and is well liked by many. It may pe- Jeep informed -read culiarly fit somebody's pocketbook. Each of our machines has recorded between ELECTRONIC MUSICAL 4000 and 5000 tapes and they have become worn and are now retired. INSTRUMENTS

By Modifications to System Richard H. Dorf Since a change in our setup was im- minent, we decided in favor of direct drive and easy speed change. Further, In one big volume, you can now learn all about the intricacies of commercial electronic our transcription service had stabilized organs, including the Allen, Baldwin, Conn - to the point where it appeared economi- sonata, Hammond, Minshall - Estey, Lowrey cal to use four machines. The Organo, and others, together with many upshot smaller instruments. Constructional details on resulted in four Berlant BRXD tape the author's Electronorgan and the simpler transport mechanisms and one BRX-P Thyratone you show how to build one of amplifier, shown in operating position these fascinating instruments for yourself. A compilation in book form of the author's iu Fig. 3. articles in Radio Electronics, brought up to Much to our surprise the Berlant date and with many additions. Price $7.50 problem turned out to be much simpler (Foreign, $8.00) . than our previous experience with Mag- Customary discounts to dealers and distributors necorder. It was thought at first that, since the Berlant has the bias and erase RADIO MAGAZINES. INC., Book Division oscillator in the amplifier section, it P. O. Box 629, Mineola, N. Y. would be necessary to build an erase Please send me . .. copies of Dorf's ELECTRONIC MUSICAL INSTRU- amplifier which would also furnish bias MENTS I enclose check money order for $7.50 each for all four machines, and that a sepa- Foreign. $8.00) . rate audio power amplifier would be Name necessary to supply audio. Final result Address of the experimentation is revealed in City . Zone State Fig. 4. A capacitance- coupled erase amplifier using a dual 50,000 -ohm poten-

78 AUDIO DECEMBER, 1956

www.americanradiohistory.com ARE Y U NURSING A DODO BIRD?

lue k HERE'S THE VERDICT: In his new Fawcett book, HI -FI GUIDE," Fig. 3. Four Berlant tape- transport mechanisms and one amplifier comprise new Donald Carl Hoefler, internationally famous setup giving some advantages over older equipment. authority on sound engineering, says this about hi -fi tone arms: "One of the newest and most revolutionary, on tiumeter on the input could be easily on RECORD, all are energized even though the other hand, is the Orthosonic V /4. This is the commercial realization of an idea which adjusted to give the desired voltage to their individual pushbutton may not be is as old as recording itself. the four erase heads. The use of the depressed. This makes it impossible to 50.000 -ohm dual pot unloaded the Ber- play back (thru the console) on one "Engineers have been attempting unsuccessfully for many years to perfect an arm which will lant oscillator to such an extent that machine and record on another. It is move the reproducing stylus in a straight line optimum bias could be achieved by tak- possible to play baek on one machine across the record, this being the path followed ing bias for all four record heads, in and record on the "master" machine, in by the original cutting stylus. When the play- parallel, from the original source. Also our case an Ampex. If you wish to erase back does not occur along this path there is said to be tracking error. Various approaches there was sufficient audio to drive the a certain portion or particularly all have been tried in attempting to minimize this, heads with no additional amplifier. Flat after a certain portion, pressing the such as very long tone arms, curved arms, offset response from 40 to 10,000 cps at the record button on an idle machine will cartridges and jointed parallelogram arms. But 7.F ips is easily attainable with no audi- erase the desired portion going through none of them has ever done the job perfectly. ble distortion. The play heads go through another machine operating on play back. "The design problems here are obvious. In ad- the selector switch to the Berlant play- All in all this setup is proving very dition to straight -line movement, it is essential back amplifier. satisfactory and the saving of $600 in that this movement be virtually frictionless. And it was with this latter requirement that most With this setup if any one machine is amplifiers is not to be overlooked. designers have had to admit defeat. Now, however, the developers of the Orthosonic claim to have licked the problem, and the preliminary evidence would indicate that the claims are RECORD HEADS well founded. If so, they have absolutely nothing to worry about. If it lives up to its promise, TO ORIGINAL AUDIO AND BIAS CONNECTIONS the Orthosonic arm will make pivoted tone ON BERLANT AMPLIFIER Q El arms as dead as the dodo bird." PINS 3 AND ON JONES PLUG ORTHO -SONIC V '4 6AS7G ERASE AMP HAS SOLVED THE PROBLEM! Hundreds of enthusiastic users have al- - IDh BERLANT ERASE IPT ready discovered that the ORTHO- TO OUTPUT OF BULANT SONIC V/4 tone arm offers new depths OSCILLATOR o31:°3° of beauty in reproduction which conven- PINS I AND 2 ON JONES PLUG 1000 tionally pivoted arms cannot bring out. More, it permits the stylus to ride the center of the groove; it makes old records .I sound like new; preserves record life and POWER FROM SEPARATE SUPPLY stylus wear!

4PLAYBACK HEADS MODEL # 100 112" size I .. $35.95

El El MODEL #200 I Transcription ) $44.50

e 1 I TO BERLANT MODEL ## 300 I Binaural) .... $59.50

PLAYBACK AMP Leading hi -fi dealers everywhere now demonstrate the ORTHO -SONIC V /4. Ask for it, or write to us for descriptive literature. Fig 4. Using one erase oscillator and an erase amplifier enables the station to MECHANICS ILLUSTRATED, Hi-Fi Guide, Published employ only one amplifier to record on four machines simultaneously. by Fawcett Publications, Inc.

AUDIO DECEMBER, 1956

www.americanradiohistory.com IMPROVE SEMI -SOLID ENCLOSURE your 75 lbs. and have a density of 1.8. They are not as good as slate, which has a density of 2.9, but they are much r AMPLIFIER 1 cheaper than slate and better than 11/4 -in. 1 plywood. f in I UNMOUNTED SRAM* 5 ways E11 Dimensions and drawings for the two 1 I .dnn.d- back panels and the top and bottom panels are not given, as no one will i i

probably wish to duplicate the carpentry --11 previously referred to. However, the unit I 1 I 1 measures 20 in. along each back panel into the corner; thus the top and bottom can be cut from one 24 -in. square of 3/4 -in. plywood. If a half -sheet (2' x 8') is purchased in the first place, the re-

maining 24 x 72 -in. piece is more than I .10 \^ sufficient to provide for the two back IL zt panels and reinforcing strips for top and bottom panels. The 4' x 4' x 1/2" 10 leo FREQUENCY IN PER SECOND sheet of asbestos- cement board cost $6.00 CYCLES in Montreal ; the birch hardwood corner Fig. 5. Impedance curves of loudspeake posts (which had to he radial -sawed) cost enclosed in the housing described by the $6.50, and the half sheet of plywood cost author, and in open air (dotted curve). ,NO' $5.60. Even with the few extras such as with the the front grille, hardware, and varnish duction of male speech is excellent. Ap- stain, the total cost of unit was under preciable output exists at 31 cps from $25.00. From Fig. 2 it will he seen that the Cook frequency record and although Amperex the asbestos cement board was given no separate tweeter is used, the integral several coats of varnish stain as a mois- 6 -in. duplex cone appears adequate up RECTIFIER GZ34 ture sealer; also that king -size snap - to 12,000 cps. This duplex cone is visible A LOW- IMPEDANCE, INDIRECTLY fasteners are used to hold the front in Fig. 2 through the screen of rubber- HEATED, FULL -WAVE RECTIFIER grille in place. ized under -rug anti -skid netting used to WITH 250 MA OUTPUT CAPACITY The internal volume is approximately protect the cone from probing little The unique AMPEREX GZ34 replaces 3.5 cu. ft. and free resonance of the fingers. without circuit changes, in the speaker is 27 cps. The curve in Fig. 5 So-if you can't accommodate a slate - majority of amplifier circuits, an speaks for itself -note that the "peaks" panelled concrete enclosure, settle for a entire line of popular, heavy -duty 5volt rectifiers -5Ú4G, 5V4G, 574, etc. at 79 and 89 cps represent a rise of only semi -solid one made from asbestos -ce- - with the following benefits: I db. There is no boominess and repro- ment board.

Better voltage regulation due to lowered power supply impedance; Higher power supply output voltage for more power; Added filter condenser protection due to reduced ripple; Cooler operation due to lower voltage drop; Protection of costly power output tubes through delayed warm-up

OTHER Amperex TUBES FOR HIGH-FIDELITY AUDIO APPLICATIONS:

EL84/6B05 9 -pin power pentode; 17 PP 6CA7 /EL34 High power pentode; 100 W PP EF8616261 low -noise high -µ pentode ECC81 /12AT7 Low -noise mediumµ dual triode ECC82 /12AU7 low -noise lowµ dual triode ECC83/ I2AX7 Low -noise high -µ dual triode EZ80 /6V4 9 -pin rectifier; cathode; 90 oto. EZ81 /6CA4 9 -pin rectifier; cathode; 150 ma.

At All Leading Electronic Ports Distributors

Amperex ,k3 ELECTRONIC CORP. 230 Duffy Ave., Hicksville, Long Island, N.Y. Fig. 4. Details of the front ponel, speaker mounting board, and the hardwood corner post to show how the front corner of the cabinet is assembled.

80 AUDIO DECEMBER, 1956

www.americanradiohistory.com COLLEGE MUSIC ROOM enta ¡,.t p, :'ltl men mtra as the floor is level. The treble from the speaker was directed toward the audience. This, judging from the comments, was where the greatest dis- crepancy between the live and recorded sound sources was observed. It represents a most difficult situation for a recording engineer who refuses to attenuate the treble to any extent. Are you Boom Conscious?.. . The experiment was quite successful in showing what the equipment could do Most people know by this time that many, expensive advertising and high -pressure sales if not most, loudspeaker enclosures . re- promotion. and in creating interest in the new music gardless of size or price . . boom. Boom is And so it goes, even though, actually, no that dull, heavy, toneless thud often heard at one ever heard boom from a live orchestra. room. There were considerable delays in low frequencies. Boom is also called "one -note And since a live orchestra is not a boom -box. the completion bass" or "juke box bass." It is an inherent why should anyone want a boom -box in his of the building. At the characteristic of so- called "resonant" enclo- home? Fortunately, no one has to buy a boom. time of dedication ceremonies, the music sures. Boom is nothing but distortion, and any box. speaker system that booms is not high fidelity. To those who want live -music facsimile in. room equipment was one of the few Notwithstanding this and believe it or not, stead of boom, competent sound engineers un- things in operation in the new wing there are still people wlso will spend hundreds, equivocally recommend THE BRADFORD and even thousands, of dollars for prime ampli- PERFECT BAFFLE. IT DOES NOT BOOM (although the decor of the room was not fiers, tunen, etc., and then go out and buy a EVER. The result is clean, true bass. complete) and boom -box. Why? This is accomplished by a new, patented device was well received by the A noted psychiatrist undertook to find the based upon a scientific principle. It is not a many visitors. answer. He found that (I) some people mistake bass-reflex or folded horn. mere loudness (so -called "augmented" bass) Moreover, it satisfies every other criteria of At the time of this writing the music for true bass; (2) others are unable to tell the the discriminating audiophile: Compactness: room had difference between true bass and boom; (3) 12" x 12" x 9" for 8s and 10s; 17" x 17" x 14" been in regular operation for some think boom is bass; (4) others think for 12s and I5s. Finest Construction and Finish. over a month. The components chosen boom is bass became it comes from large 1/4", genuine mahogany, korina blond, walnut and /or expensive enclosures; (5) others have and ebony veneers; and unfinished birch. Econ- are functioning so well that, playing a fixation for expiring myths, such as, "the omy: from $34.50 to $69.50. constantly before a bigger the box the better the sound "; (6) If you are boom conscious, want live -music critical audience, some innately resist progress and never seem facsimile instead of those dull, heavy, toneles, music coming from the main loudspeaker able to adjust themselves to better things as thuds, hie to your dealer or write for litera- they come along; (7) others are impressed by ture. via the control room has received no critical comments aside from frequent BRADFORD & COMPANY, 27 East 38th Street, New York 16, N. Y. recommendations for equalizer changes and criticism of older records. Considering the size of the music room and the performance of the system, one professor described it this way, "It's THE OUESTION: Do you know where you can find information about bringing the concert the current articles in magazines about microwaves, loudspeakers, television hall into the concert repairing, electronic musical instruments, traveling -wave tubes, transistor hall. amplifiers, oscilloscopes, or any other electronic subject?

THE ANSWER: AUDIOCLINIC (from page 58)

smaller the circumference, the greater the high- frequency loss will be. It can easily be seen that though the E rotational speed of the table remains unchanged, the speed which really counts is constantly being reduced. In linear speed, FORMERLY the rotational speed changes so as to maintain a constant speed of disc material passing under the recording needle. This keeps MDIOFILE the frequency response constant over the entire playing surface, with the upper limit Not a new publication, but one which for over ten years has served engineers, of that response being determined by the libraries, experimenters, researchers, hobbyists, radio amateurs, radio and TV linear velocity chosen. repairmen, and anyone else connected with radio or electronics. Covers radio, This has never been used commercially television, electronics, and related subjects, and published bi- monthly as a for high fidelity sound reproduction. The cumulative index throughout the year, with the last issue of the year an only products which make use of this Annual which may be kept as a permanent record of all electronic periodical principle are office dictating machines I iterature. produced by Gray Audograph Co. In these Magazines, devices, the recording LECTRODEX -the electronics index -is now published by Radio starts at the center Inc., and has expanded to include the contents of twenty magazines in of the disc, meaning is been that this the point the radio and fields. by only, $3.00 for one at which the rotational speed is greatest. electronics Sold subscripi.'ln year, $5.50 for two years. Back Annual issues are available from 1946 through 1955, know where to find the information Amplifier Trouble 504 per copy. Subscribe now and you often need so badly. Q. I have encountered a phenomenon that I am at a loss to understand. Using MAGAZINES, an amplifier with a conventional ultra - RADIO INC. lin, ar circuit with 5881's in the output, P. O. Box Mineola, N. Y. performance is beautiful -hunt, distortion, 629, anti so on, at a minimum. However, I find

AUDIO DECEMBER, 1956 81

www.americanradiohistory.com that if the input of the amplifier is fed a sudden high -level signal or the input is "shocked" by touching the input cable, the effect is that of an extreme overload or block: volume of output will drop con- R E I I siderably and distortion is extreme. This P C S ON condition will exist until it gradually fades or bleeds away, taking five to ten minutes The marked similarity between the -or I can relieve it by turning off the watchmaker's art and the craftsmanship amplifier, pulling one of the 5881's and required to produce a precision shorting either the plate or screen socket cartridge connection to ground. Can you tell me what can be aptly illustrated by an examina- is causing this trouble and how I can tion of the famous FAIRCHILD Micrad- eliminate it? Jackson C. Ream, Albuquer- just Cartridge. que, New Mexico. A. The circuit design of such amplifiers is very stable, so that the difficulty lies in some component, Meticulous care and delicate assembly faulty or perhaps an accident in wiring. Assuming that the unit has are basic to both products. In addition. been wired properly, check all tubes, espe- adjustments are provided in the finest cially the output tubes. Much time has been of watch movements to regulate lost by many a serviceman by looking for a bug which proved more nor performance by compensating for to be nothing less than a defective tube. Make the am- minute differences in manufacturing plifier block, and note the colot of the out- tolerances as well as variations in put tube or tubes. One or both of them material. Similarly the MICRADJUST may have a blue coloration. This means that the tube is gassy. A gassy tube conducts by feature permits regulating the magnetic ionization, allowing it to draw high current. gap to precisely fit the moving coil The effect of the signal voltage supplied to assembly.* The result is uniform the grid will be small and the output will flux gap, proper centering of stylus be distorted. If this condition is allowed to continue, there is danger of damaging other arm and correct damping. It assures best components. possible cartridge performance which If the tubes appear to be all right, you is immediately apparent to the may have an open grid return resistor. critical listener. These are resistors which connect the grid of a tube either to ground or to a point Write for datai Is on FAIRCHILD audio products. where fixed bias is applied, or perhaps to some portion of a phase splitter network. FAIRCHILD RECORDING EQUIPMENT COMPANY If such a resistor were to become open (in- 10 -40 45th Avenue, Long Island City 1, New York finite resistance), the grid of the tube would become more negative than it should be for proper operation, and the plate current would be at least partially cut off. Such troubles can also be caused by in-

I I I I I I I I I I I I I I I I I II I I I II I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I II I I I, I I I I I I I I V I V I I I I I I I I I II II I I I I I I I V I I V I I I V I I I I I I I I I II I I I II I I I II 1 1 1 1 1 1 1 II I I I I, I, termittent coupling capacitors or cathode resistors. ,vd anthoo9`1 GRAPHICAL SOLUTIONS (from page 24) 3rd and the magnitude the [Rs +Xes]i IZI = =l Reprints of articles which appeared in AUDIO %o [Rft +i C [to'C'R' +i]f from July 1952 to June 1955. 124 pages of arti- 1f= cles of greatest interest to the serious hobbyist. which answers are identical to the analytical solutions to be found in text- The AUDIO ANTHOLOGY and 2nd AUDIO ANTHOLOGY books. are no longer in print.

CUT OUT MAIL TODAY! - - C2 C3 LI Book Division, Dept. 10 E--- --IE-- -iE- Z3 *4 Radio Magazines, Inc., Z2

P. 0. Box 629, Mineola, N. Y. A I CI Ri i- nvVr- RZ 03 Gentlemen Enclosed is check money order for $ . Please send me

copies of the 3rd audio anthology (paper cover) @ $2.50 each Fig. 13. Circuit of Fig. 12 redrawn for copies of the 3rd audio anthology (board cover) @ $3.50 each purpose of analysis. Name (please print)

Address To Figure 6

City Zone State In Fig. 6 the angle

a, IIYIIIIIIIIIIIIII III,I,II,III,Ii iI. n,na,nnl,all III,( IIII, II,IIIIIIIIIIIIIIIIIIIIIII,IIII III IIIIIIIIII 1111111 III 1111111 VIII II,II 1111111 III VIII VIII VIII IIIIIIIIIIII IIIIIIIII IIIIIIIIIIIIIIIIIIIIIIIIIIM OBC= AOC

82 AUDIO DECEMBER, 1956

www.americanradiohistory.com Then tions illustrated in Figs. 7 and 8 one proceeds exactly as described above, ex- = -tan -' =- tan I RwC (2) c cept for the sign of the reactance which .RADIOMINC, I is now positive instead of negative. From the two similar triangles

OC:OA =OB:AB To Figure 10 and SUGGEST (IA xOB The two triangles DAB and DOC are OC (3) similar. Then AB FOR BA : OC = DA : OD (7) Ant = OAt +OB' (4) DA =OD +OA and OA =AB CHRISTMAS GIVING ... Substituting the values OA = R and by construction. Substitute these into O B = Xc into Eq. (4) and then into Eq. Now ín stock . . . complete tape F.q. (7) : we stereo (.) get library. Livingston ... A -V .. . RXc. R BA : OC= (OD +AB) : OD Bel Canto . . . Concert Hall Society (5) and OC= Stereotapes ... Concertapes . . . V Re + Xe3 Rt HiFi JCr+, BA x OD= (OD +AB) x OC Tapes ... Jazztape . .. Omega -

tape RCA Victor . . . whence ...... EMC many others . and NOW! ! ' Re being ODxOC --wC BA= OD - OC SONOTAPE h' definition, Eq. (5) becomes Substitute Never before have you heard such fre- OC= quency response, especially in the OC - (6) XL=wL highs. Made from WESTMINSTER MAS- V1 +wtC2R2 and TERS which are unsurpassed in fidelity The value arrived at in Eq. (2) is and SONOTAPE'S copying tech- OD= X0=o=-roC nique admits no loss, or distortion! identical with the expression derived You can't get closer to an actual per- analytically for the phase angle; that in into Eq. (8) and get formance than a SONOTAPE stereo- Eq. (6) is identical with the magnitude. phonic . . . listen to just a single L measure, and compare! Thus the vector OC does represent the C wL impedance of a resistance and a capaci- BA = IMMEDIATE DELIVERY! 1 1- wtCL tance in parallel. - wL wC SWB 8001 -BACH: Toccata and Fugue, D -min; Passacaglia and Tc Figures 7 and 8 which is identical with the analytical Fugue, C -min. Carl Weinrich, Co prove the validity of the construe- solution. organ of Varfrukyrka, Skanninge Sweden SWB 8002 -BEETHOVEN: Moon- light and Pathetique Sonatas; Raymond Lewenthal, piano SWB 8003 -STRAVINSKY: L'His- toire Du Soldat; Ars Nova, Man- dell, cond.

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Fig 14. Graphical solution of problem of Fig. 12. The step -by -step progress is EONARD RADIO, INC. described fully in the text. lore >. N COnlnnel r 0311

Aí :)10 DECEMBER, 1956 83

www.americanradiohistory.com FM TUNERS CLASSIFIED Rates: 10e per word per insertion for noneeseeerslai advertisements; 25, per word for ammenlal amt. (from page 34) tisemenh. Rates are net. and no dlsaants will be allowed. Copy mast be accompanied by nmittance ln fall. and mast reach the New York osa by the tit of not affect tuning of normal stations, the the month preceding the date of Issue. other trap can be adjusted at about 10.3 inc. In this way the response curve on THE AUDIO EXCHANGE has the large,. this side is steepened and the adjacent - selection of new and fully guaranteed used channel selectivity improved. If one trap equipment. Catalog of used eitniptlletst on request. Audio Exchange, Dept. AE. 159 -10 hill - p will not eliminate two -spot tuning, tune side Ave.. Jamaica 32. N. Y. AXtel 7.7377; the other trap to this (11.1 me) fre- 367 Mamaroneck Ave., White Plains, N. T. wH 8- 3380, quency also. AUDIO EXCHANGE EXCHANGES AUDIO No further alignment is necessary. The detector, HIGH -FIDELITY SPEAKERS REPAIRED if no error in wiring has Amprite Speaker Service been committed, requires no adjustment. TO Vesey St., New York 7. N. Y. BA 7-2580 If distortion -free results cannot be ob- WANT A VERY LOW REASONANCE tained, check the 10.7-me channel for SPEAKER? regeneration, oscillation, or a badly dis- Ask your dealer to demonstrate the Racon torted and too narrow Floating cone, foam suspension loudspeaker. band -pass. Or write for literature and prices. Itacon Elec- The simplicity of the alignment proc- tric Co.. 1261 Broadway, New York 1, N. Y. ess, makes it possible to keep the tuner HI -FI RECORD CHANGLK DuKane 30/50 cycle automatic tone gener- quality "intermix" changing at peak performance by occasional re- ator for film -strip recording. reed Presto SK at the new low price of adjustment of the trimmers using the 12 -In. recorder. Cinema Engineering 500 -ohm tuning eye. INAB) recording diameter equalizer. Sound 1957 MODEL Unlimited, 112 South Ave., Erle. Pa. $2995 The simplest way to build the corn D 10Q audiophile net plete amplifier would be to purchase the Free monthly HI -FI bulletin. Write for quotation ou any components. Sound Repro- Collins Audio Products Company's IF -6 duction. Inc., 34 New St., Newark. N.J. Mit- chell 2 -6816. AT LEADING NI -rl . MUSIC CENTERS amplifier and modify it to the new cir- WRITE TODAY FOR COMPLETE LITERATURE cuit. The modifications would not be Long playing records 20 to 50% discounts; great and the use of this chassis would brand new factory fresh ; unplayed : all lalnls. ERCONA CORPORATION Send 214 for catalog to Record Discount Division) eliminate punching and assembly. The Club, (Electronle 1108 Winhern, Houston 4, Texas. 551 fifth Ave., Dept. 40 Now Yorke N: Y. third i.f. tube would be replaced by a Circle 84A 6BE6 as a converter, and the stage re- 6- Element BROAD-BAND FM ANTENNAS. wired. The All seamless aluminum. $10.95 ppd. Wholesale discriminator transformer Supply Co., Lunenburg 111, Muss. would be converted into a 10,9 -me oscil lator coil by shorting out the discrimina- Sacrifice Fisher tuner, Heath amplifier, Jen- sen G -610, cabinets, records. LOrraine 8.4729. for everything in hi-fi tor winding and tapping the plate wind- GET THE MONET- SAVING 1957 ing about one -fourth of the way up from Write for specifications, prices. and sample the low deal on truly High Fidelity ItEt'OI111ING, end. This transformer would PRESSING, and DUBBING. Iielirich Record- ALLIED CATALOG then replace the fourth i.f. transformer, ing Service, R #1, Wescoesville, l'a. which could be used at the front -end Disc or tape recordings from your tape. output transformer if a whole new re- Complete quality servire. Write Sound Ln- featuring the ceiver is constructed. The spot now oc- limited, 112 South Ave., Erle, Pa. world's largest cupied by the discriminator transformer stocks of systems would be filled in with a socket to take 8 components the 6AU6 which was the third i.f. and will now be the second limiter. The whole Lnpituprter,.t section from the converter to the detec- free! tor would now be rewired into a 200-kc ENJOY THE ADVANTAGES OF A Small MID -WEST SEND FOR IT channel and detector. Only one addi- CITY tional tube, the 6BE6, and a few re- Immediate openings for engineers with experience Here's your complete money- saving guide sistors and capacitors, would be neces- in any of these fields: to Hi -Fi. Shows you how to select a custom Hi -Fi music system for your home at sary to make the change. Audio no more than the cost of an ordinary TV or High Frequency phonograph. Tells you what to look for The Collins FM -11 kit thus modified AM Broadcast Transmitters and how to save money. Offers the world's should produce a receiver with useable Communications largest selection of complete Hi -Fi systems as well as individual amplifiers, sensitivity better than 1 microvolt, equal- Mechanical tuners, changers, speakers, enclosures and Standards -Numbering Systems accessories. Want to build-your-own?- ling the sensitivity and surpassing the Technical Writing see the famous Hi -Fi KNIGHT -KITS. For fidelity of the $300 to $600 monitoring everything in Hi -Fi -for everything in Elec- Give your family a break. Get away from The Traffic t ronics, get the men 1957 ALLIED Catalog. and relay receivers used by FM broad- and rush. cast stations. Advancement. Complete employee benefits. Send details and photo to Personnel Director. ALLIED RADIO HI-FIRCEN ER If the amplifier is used as an outboard ALLIED RADIO GATES RADIO COMPANY CORP. Dept. tL -126 accessory to a present FM receiver, no QUINCY. ILL. 100 N. Western Ave., Chicago 80, III. attempt should be made to use a Com- Cl Send FREE 1957 ALLIED Catalog mon power supply, for instability in WANTED Service manager for well Name the 10.7 -mc channel would surely re- known High Fidelity establishment. Must sult. Indeed, when used as a boosting Address be thoroughly familiar with all types of amplifier, it would be well to shield the High Fidelity equipment and problems in City Zone_Stafe whole rig and place it a foot or more order to take complete charge. Box 1201, .ma present receiver. ttrcae 848 , from the Audio.

84 AUDIO DECEMBER, 1956

www.americanradiohistory.com PROFESSIONAL pf K DIRECTOR% .9aciask.f nom... pre- finished Kits Randolph (Randy) Ketcham, widely known and highly regarded in broadcast and recording circles, has joined Cook 1111 ceali;ucabcaly Suce l944 Laboratories, Inc., Stamford, Conn., as national sales manager . Robert G. PFK 120 150 Bach has rejoined Fairchild Recording Equipment Company as sales manager; 1 HOLLYWOOD ELECTRONICS formerly with Fairchild in a similar ca- designed by PFK-500 DISTRIBUTORS OP 14I-P1 COMPONENTS pacity, for the past year he has been advertising manager of Harman -Kardon, Paul Klipsch Inc. . Personnel realignment of Altec i Companies, Inc., finds Bert Ennis, in Now you need only a screw. PFK-300 charge of publicity, dividing his time be- driver tc put together a furni- tween New York offices and the manufacture- finished Klipsch speaker enclosure, indis. 1460 YIre A.t. Angelo. 46,CiBwlbtr 3-420e turing plant of Altec Lansing Corporation tngulshable from factory -assembled Rebel 3, 4 or r,n the west coast; principal assignment Also available as conventional, unfinished lot, Circle 85C is to establish liaison between Altec's east and west publicity activities. S. M. Ander- son, formerly merchandising manager of Write for Complete Catalog!

Altee Service Company at the firm's New 30 pose, . . I ether h, h khs . 29 York headquarters, has been appointed DIequipment cabinets ... 4 matched ,pecker purchasing agent for Altec Lansing Cor- systems ... 20 hifi accessories. poration at the company's manufacturing HIGH -FIDELITY HOUSE plant in Beverly Hills. C-.bin-,rr Most complete stock of Audio Appointment of Nils Hillstrom as na- . . in the West tional sales manager has been announced components by Robert D. Newcomb, president of New- Phone: RYan 1 -8171 comb Audio Products . . . Promotions at University Loudspeakers, Inc., include 536 S. Fair Oaks, Pasadena I, Calif. Lawrence J. Epstein, who has been named di ,''tor of sales and merchandising, and Charles Ray, who has been named jobber Circle 85D sales manager. Arthur L. Poster has re- signed as advertising manager of the special products division of Stromberg- Carlson Company to join J. H. Sparks, GIBSON GIRL TAPE SPLICERS Inc., Philadelphia distributors, as hi-fi sales manager . . . Appointment of Neal Cabinart W. Turner as merchandising manager of 99 North I1th Street splices in a wink! Heath Company has been announced by NO SCISSORS, Brooklyn 11, N. Y. NO r0. IlOfs. Robert Erickson, Heath president. Prior to joining Heath in 1950, Turner was with ,h riz ana kits for hifi the Hallicrafters Company. At Your Dealer. Circle 85A ROSINS INDUSTRIES CORP.

Circle 85E Natetet NOW the finest in 1i-Fi Appointment of Francis C. Henley as high fidelity general manager of a newly -formed divi- featuring MCVliffer,, sion of Minnesota Xining and Manufactur- NIGH FIDELITY COMPONENTS ing So., has been announced by Robert L. %M1-estbee, vice -president in charge of 3M's 6X9 COAXIAL Electrical Products Group. The division, to be known as BEinoom, will continue elec- SOUND tronic research and product development C O R P O R A T I O activities formerly conducted by the electronics 121 V. WI. l.l. 1S, Calif. 111 1211 division of Bing Crosby Enter- 1l,pc prises, Inc. John T. Mullin has been named research director. A group of Crosby re- Circle 99F search staff members, headed by Mullin and Wayne R. Johnson, have also joined 3M. The Mincom division will headquarter in new office and laboratory facilities in CANADA the Los Angeles area. The exact site has High Fidelity Equipment not been selected. Magnecord, Inc., Chicago, has estab- commutate Lines Complete Beryls. lished another division, MagneMatic, to HI -fl ke,orde - Component. specialize in the development and manu- earl Aecesiorlee facture of magnetic tape recording equipment for industrial applications, particu- ... ideal for original, replacement, or larly in the fields of automation and ad- remote installa-ion - plus auto rear LECTRO-UO10E vanced instrumentation. This move, an- deck - -- wherever high quality ex- SOUND SYSTEMS other step in the company's program of tended range speakers are desired. SAI OUNOAS ST. WEST. TORONTO, CANADA. planned diversification within its profes- Cinaudagraph cffers a superior qual- sional field, was given initial impetus by ity speaker for every Hi -Fi need - Circle 99C the purchase of all designs of A -V Manu- facturing Corporation. Charles Rynd, backed by the industry's only 5 -year president of A -V, has been retained as warranty. consultant. Another Magnecord subsidiary, Magna Music, Inc., supplies tape repro- 5 YEAR WARRANTY II AUTOMATIC CHANGER NEEDLE BRUSH ducers and recorded RCA tapes for com- ... ask to see it KLeeNeeDLE mercial installations of background music. ORRadio Industries, Inc., Opelika, Ala., of your dealer or write KleeNeeDlE automatically keeps manufacturers of recording and video record changer needles clean. tape, It is designed to remove th has been confirmed as a general member familiar -dust-blab- from under of th.i Institute of High Fidelity Mann - the needle point. At Your facturere. Admitted as an associate mem- Dealer ber was The Elektrs Corp., New York City, INC ROBINS INDUSTRIES CORP. Ilaysid 61, N. Y manufacturers of hi-fi records. Member- 7334 N. CLARK ST., CHICAGO 26, CABLE ADDRESS ENOTS ship of the Institute now totals 72 com- Circle 85H panies. Ciclo 85B

AUDIO DECEMBER, 1956 85

www.americanradiohistory.com AUDIO SUBJECT INDEX 1956

AMPLIFIERS Speaker enclosures--Sound. Chap. 10; Edgar MUSIC Conference amplifier for the hard -of -hear- M. Vinlchur. June 34; Aug. 22. An experiment in true-fidelity organ repro- lug buaiuess executive; Robert M. Mit- duction; Julian I). Hirsch. Apr. 26. chell. Nov. 46. EQUALIZATION Artistic integrity of the record ; Otto Meyer- Audio design chart -amplifier or loud- Compression and dialog equalization in Serra. Mar. 20. speaker impedance. Nov. 22. motion picture sound recording; Edward Experiment III - the Beta-Tron; Stan I'. Ancona. June 17. MUSICAL INSTRUMENTS White. May 28. The Conn electronic organ; Richard H. Interaction concept in feedback design; FEEDBACK Dorf. Sept. 28; Oct. 48. Norman II. Crowhurst. Oct. 38; Nov. 32. Feedback tone -control circuit; Hamilton The Schober electronic organ; Richard H. Preamplifiers and amplifiers- Sound, Chap. Rarhydt. Aug. I8. Dorf. Jan. 20; Feb. 29. 6; Edgar M. VIUci:ur. Mar. 36. Interaction cuue pt in fenlbnck design; Amplifiers. power -Suuud, Chap. 8: Edgar Normau H. Crowhurst. Oct. 38: Nov. 32. PHONOGRAPH EQUIPMENT M. Vllichur. Apr. 46. Simplitronlcs -Feedback; Harold Reed. A new turntable design ; Rubin Carlson. Stabilizing transistor amplifiers: Richard Apr. 29. Feb. 20. II. Small. Dec. 4L FILTERS PHONOGRAPH PICKUPS AMPLIFIERS. PRE - Graphical solution of Compensation for amplitude responsive electrical filters; L. phuuo pickups; R. H. Brown. 26. U. ileums. Dec. 22. Nov. Compensation for amplitude responsive Pickups, pl pickups; R. II. Brown. Nov. 26. tone arms, and needles -Sound, Chap. 5; Edgar M. Villebur. Feb. 40. High - q unlit y dun l- channel HIGII FIDELITY SYSTEM a III pi i tier; Compensation for amplitude responsive Charles W. Harrison. Jan. 19. A profession.' I -FI home Ili music system; phono pickups; R. H. Brown. Nov. 26. Preamplifiers and nngditiers- Sound. Chap. Oliver Berliner. Apr. 29. 0: Edgar M. Villchur. Mar. 36. HEM PHONOGRAPH RECORDS Transistor preamps; 11. F. Starke. Apr. 31. Design conaiderntions for hum reduction; Artistic integrity of the record; Otto Meyer - Oliver Berliner. Nov. 38. Serra. Mar. 20. AT HOME \VITII AUDIO, Lewis C. Stone Record speed and playing time; Charles P. Mur. 20; May 24; June 24. 'tuegll. Sept. LAW 10. ATTENUATORS Contracts against competitive employment: PSTCIIOACOUSTICS Care of audio attenuators; Eugene F. Albert W. Gray. 1M1. 44. An experiment in true -fidelity organ repro- ('orlell. May 44. Features of patent- Ibvusing agreements; duction; Julian D. Hirsch. Apr. 26. BRIGGS* CONCERT -1o36; C. G. McI'rond. Albert W. Gray. Dec. 4s. How loud is silence? Charles E. White. Nov. M. How long is "permanent" employment? Mar. 17. Albert W. Gray. Jnu. 26. Noise -enemy of normal hearing; Charles BROADCASTING STUDIOS Loss of ratent by delayed application. Al- E. White. Nov. 18. A somul effets console for UN studios; D. bert W. Gray. Nov. 23. Room environment- Sound, Chap. 12; Edgar Il. Jones. Sept. 26. M. Vilichur. July 22. Spehul audio console LISTENING ROOMS meets WSB -TV RECORDING. Disc needs; Bert Ennis. Sept. 24. Sound- P.00in environment; Edgar M. Vill- chur. July 22. Disc recording- Sound, Chap. 4; Edgar M. COMMERCIAL SUPPRESSOR, Villchur. Jan. 17. Time delay; Ronald L. Ives. Nov. 24. LOUDSPEAKERS RECORDERS, Tape A semicircular exponential horn; Reuben CROSSOVER Tape recorder section; C. G. McProud. Feb. NETWORKS M. Cares. Oct. 26. 27. A survey of crossover networks: Richard Audio design chart; Amplifier or loud- C. Hitchcock. Nov. 28. speaker laspeJauuce. Nov. 22. RECORDING, Equalization Interference effects with loudspeaker cross- But lites muballled; Edward over networks; J. Jordan. Aug. Compression and dialog equalization in Charles P. Buegli. Nov. 13. 13; Sept. 34. motion picture sound recording; Edward Diffaxint speaker; Abraham B. Cohen. June P. Ancona. June 17. DESIGN CHART 20. Amplifier or loudpeaker impedance. Nov. 22. Experiment Ill -the Beta-Tron ; Stun White. RECORDING, Tape may 26. Distortion in tape recording; Herman DISTORTION Future of loudspeaker design; Norman H. Burstein and henry C. l'ollak. Oct. 30. In hope recording; Herman Burstein and Crowhurst. De:. W. Multiple tape copying; R. E. Baird. Dec. 36. Henry l'ollak. Oct. 30. Improved circuit for electrostatic tweeters; Charles E. Cohn. Oct. 36. ENCLOSURES STEREOPHONIC Interference effects with loudapen ker cross- Stereophonic microphone pincement; James A folded horn design; Richard A. Greiner. over networks: Charles P. ]toegli. Nov. 13. Cunningham and Robert O. Jordan. Nov. Dec. 40. Ported loudspeaker cabinets; James Muir. 43. A semicircular exponential horn: Reuben Oct. 23. M. Cares. Oct. 20. Report on friction loading; C. G. McProud. SYSTEMS Bnlllas aubnfiled; Edward J. Jordan. Aug. June 98; July 26. A professional Hi -Fi home music system; 13; Sept. 34. Sound -Loudspeakers; Edgar M. Villchur. Oliver Berliner. Apr. 23. Concrete for loudspeaker enclosures; Phil May 46. College music room design; Merle Fleming J. \Valusck. Dee. 23. What makes a woofer? Senl J. White. and Elliott D. Full. Dec. 28. Ported loudspeaker cabinets; James Moir. May 30. Oct. 23. TONE CONTROLS Report on friction loading; C. G. McProud. MICROPHONES A versatile bass -treble tone control; Charles June 38; July 26. T. Morrow. Sept. 17. Stereophonic microphone placement ; James Sena) solid corner enclosure; H. P. Foerster. Cunningham and Robert O. Jordan. Nov. Feedback tone -control circuit: Hamilton Dec. 39. 43. Rarhydt. Aug. 18.

86 AUDIO DECEMBER. 1956

www.americanradiohistory.com TRANSFORMERS TRANSISTORS Transistor ',mimes; 11. F. Sua rke. Apr. 31.

Audio transformers can be good; Norman Simplitronics -Understanding the r's in Transistor tips and techniques: Paul Pen - H. Crowhurst. May 22. transistors; Harold Reed. Aug. 21. field. Feb. 17. Input transformer design; Norman H. Stabilizing transistor amplifiers; Richard Crowburst. June 27; July 17. H. Small. Dec. 47. TUNERS Output transformer design; Norman I1. Transistor action; Paul Penfield. Oct. 15. Increasing sensitivity and lowering distor- Crowhurst. Sept. 20. Transistorized AM tuner conversion; Ed- tion in FM tuners; Joseph Marshall. Dec. Transformer design considerations for zero- win Bohr. July 15. 30. impedance stages; N. R. Grossner. Mar. Transistor bins stabilization; Paul Pen- Transistorized AM tuner conversion: Edwin 27. field. May 34; July 20. Bohr. ,July 15.

AUDIO A UTHOR INDEX 1956

Ancona, Edward P. Jr. Ennis, Bert McProud, C. G. Compression and sound equalization in mo- Special audio console meets WSB -TV needs; Briggs concert -1956; Nov. 54. tion picture sound recording; June 17. Sept. 24. Report on friction loading; ,lune 38; July 26. Tape Baird, R. E. Fleming. Merle, and Elliott D. Full recorder section; Feb. 27. Multiple tape copying; Dec. 38. College music room design; Dec. 28. Mitchell, Robert M. A conference amplifier for the hard -of -hear- Barhydt, Hamilton Full. Elliott D., and Merle Fleming ing business executive; Nov. 48. Feedback tone- control circuit: Aug. 18. College music room design; Dec. 28. Moir, James Berliner. Oliver Foerster, H. P. Ported loudspeaker cabinets; Oet. 23. A professional hi -fl home music system: Sensi -solid corner enclosure; Dec. 39. Morrow, ('harles T. Apr. 23. A versatile bass- treble tone control; Sept. Design considerations for hum reduction; 17. Nov. 38. Gray, Albert W. Contracts against competitive employment; Penfield, Paul Boegli, Charles P. Oet. 44. Interference effects with loudspeaker cross- Transistor action; Oct. 15. Features of patent -licensing agreements; Transistor bias stabilization; May 34; July over networks; Nov. 15. Dec. 48. Record speed and playing time; Sept. 19. 20. How long is "permanent" employment? Transistor tips and techniques; Feb. 17. Bohr, Edwin Jan. 28. Pollak, Henry and Herman Burstein Transistorized AM tuner conversion; July Loss of patent by delayed application; 15. Nov. 23. Distortion in tape recording; Oct. 30. Brown, R. H. Greiner, Richard A. Reed, Harold amplitude responsive phono pickups; Nov. A folded horn design; Dec. 40. Simplitronics -Feedback; Apr. 29. 26. Grossner, N. R. Simplitronics -Understanding the r's in transistors; Aug. 21. Burstein, Herman and Henry Pollak Transformer design considerations for zere- Distortion in tape recording; Oct. SO. impedance stages; Mar. 27. Richardson, Marrie K. N. Y. High Fidelity Show preview; Sept. 48. Ilamvas, Cares, Reuben M. L. U. Graphical Dec. A semicircular expontial horn; Oct. 28. solution of electrical filters; Small. Richard H. Stabilizing transistor amplifiers: Dec. 47. Carlson, Rubin Harrison, Charles W. Starke, H. F. A new turntable design; Feb. 20. High -quality dual channel amplifier: Jan. Transistor preumpa; Apr. 3,. 13. Cohen, Abraham B. Stone, Lewis C. The Diffaxial speaker; June 20. Hirsch, Julian D. At home with Audio; Mar. 20; May 24; Cohn, Charles E. True fidelity organ reproduction: Apr. 26. June 24. Improved circuit for electrostatic tweeters; Hitchcock. Richard C. l'lllchar, Edgar M. Oct. 36. A survey of crossover networks; Nov. 28. Sound: Chnp. 4 -Disc recording. Jan. 17; Corlett, Eugene F. ('hap. 5-Pickups, tone arms, and needles, Care of audio attenuators; May 44. Ives, Ronald L. Feb. 40; Chap. 6- Preamplifiers and control units. Mar. 38; Chap. S -Power am- A time -delay commercial suppressor:. Nov. plifiers. Apr. 49; Chap. 9- Loudspeakers, Crowhurst, Norman H. 24. May 46; Chap. 10- Speaker enclosures. Audio transformers can he good: May 22. June 34, Aug. 22; ('hap. 12-Room en- Future of loudspeaker design Dec. 19. vironment. July 22. ,tons, D. D. Input transformer design; June 27; July 17. A sound effects console for UN studios: Walusek, Phil J. The interaction concept in feedback design; Sept. 26. Oct. 38; Nov. 32. Concrete for loudspeaker enclosures; Dec. .Jordan, Edward .1. 25. Cunningham, James, and Robert O. Jordan Bailles unburned; Aug. 15; Sept. 34. White, Charles E. Microphone placement; Nov. 43. How loud is stlence? Mar. 17. Jordan, Robert O., and James Cunningham Noise-enemy of normal hearing: Nov. 18. Microphone placement ; Nov. 43. Dort, Richard H. White, Saul J. The Conn electronic organ; Sept. 28; Oct. What makes a woofer? May 30. 48. Marshall, Joseph The Schober electronic organ; Jan. 20; Increasing sensitivty and lowering distor- White, Stan Feb. 23. tion in FM tuners; Dec. 30. Experimenl III -the Beta -iron; May 28.

AUDIO DECEMBER, 1956 87

www.americanradiohistory.com Low -Cost Hi -Fi with the If You're a Connoisseur... SOUND ECONOMY you'll want a of ADVERTISING TURNTABLE INDEX

Acoustic Research, Inc. 38, 74, 75 Allied Radio Corporation 84 Altes Lansing Corporation 10, 11 $1 1 000 4B American Electronics, Inc. 6, 7 Amperex Electronic Corporation 90 Compare the Connoisseur with any turntable and you'll marvel at its Ampex Corporation 63 performance. Non -magnetic, 12" Audak Co. 72 lathe- turned table; precision ground STENTORIAN Audiogersh Corporation Cover 3 spindle; phosphor bronze turntable LOUDSPEAKERS bearing. ±2% variation provided for Barker Sales Co. 88 all 3 speeds; hysteresis motor. Bell Sound Systems. Inc. 71 Bell Telephone Laboratories 18 TURNTABLE: Rumble- better than 50 THE SOUND THAT STANDS ALONE... Bozak, R. T., Sales Co. 57 db down; Wow -less than 0.15% of Now, with W iR Stentorian.s, you can enjoy Bradford Cr Company 81 rated speed; Dimensions: 13%x15% ". high- quality high fidelity at unbelievably low. British Industries Corporation PICKUP: Frequency Response 20- low cost! facing p. I, 3, 13 20,000 cps ±2 db at 33% rpm; -Effec- Manufactured in England by world -re- mg; Impedance nowned Whiteley Electrical Radio Company Cabinart 85 tive Mass -4 -400 originators of the commercial per- ohms at 1000 cps. - first Capps Cr Inc. Company. 51 manent magnet loudspeakers in 1927 - Stentorians provide a beauty and realism that Cinaudagraph, Inc. 85 has won the unqualified praise of nearly Classified Ads 84 every leading audio critic and user, both here Collare Record Changers 9 and abroad. But 1st-acing is ?inhering! Hear the W/B Crest Records. Inc. 78 "Dynabalanced" tone arm with Stentorians at your very first opportunity Mark II super -lightweight pickup and discover for yourself why these Dauntless International 61 w /diamond stylus . - . w /SaP- distinguished units are the leading low -cost De Jur Amsco Corp. 55 $49.50 speakers in the world today. phire stylus $34.50. Electro-Sonic Laboratories, Inc. 67 15" STENTORIAN WOOFER Model HF 1514 Electro-Voice, Inc. Cover 4, 76 ERCONA CORPORATION ( Electronic Division) Response, 25 4.000 cps.; bass resonance, Electro -Voice Sound Systems 85 35 cps.; power rating, 25 watts; 10 lb. 551 Fifth Ave., Dept. New York 17 Elgin National Watch Company 2 ®, Magnet System $89.50 In ('anada, rite antral Elrrtrrn r,,,,,vonn Ercona Corporation 12, 88 m r h 12" STENTORIAN EXTENDED RANGE LOUDSPEAKER 84, I,, itrd. ,;Pan=ed Road, Toronto Model HF 1214 Circle 88B Response, 25 14.000 cps.; bass resonance. Fairchild Recording Equipment Co. 39 cps.; power rating, 15 watts; 51/2 lb. Fisher Radio Corporation 43 -46 Alcomas Magnet System $49.50 General Electric Company 35, 62 STENTOR IAN GTodmans Industries Ltd. 53 UNIVERSAL IMPEDANCE LOUDSPEAKERS WITH 4 -16 OHM VOICE COILS -8 Heath Co. 16, 17 For HI -FI and Model HF 1012 -U (10 ") Response, 30 - 14.000 High Fidelity House 85 cps.; bass resonance. 35 cps.; power rating, Hollywood Electronics 85 10 watts; 12,000 gauss; 2 lb. Alcomax Mag- net System $17.95 JansZen Speakers I Neshaminy Electronic TAPE RECORDER FANS! Model 812 -U (8 ") Response. 50 - 12,000 cps.; bass resonance. Corp.) 66 65 cps.; 12.000 gauss; 2 lb. HOW TO SELECT 8 USE YOUR TAPE RECORDER Alcomax Magnet System. Other specifications Jensen Manufacturing Company 31 as above. $13.95 by David Marl, Model HF 816.1 as above but with 16,000 gauss; Kierulff Sound Corporation 85 Written for the user of magnetic tape re- 31/2 lb. Alcomax Magnet System $29.50 corders-and to serve as a guide in selecting Laboratory of Electronic Engineering ... 49 a machine that most suitably meets his or her STENTORIAN EXTENDED RANGE SPEAKERS individual requirements. For all those win. Lansing, James B., Sound, Inc. 59 have little or no formal training in the scieuii Model HF 810 (8 ") Response, 50 - 12,000 cps.; Leonard Radio, Inc. 83 of electronics. bass resonance, 65 cps. $10.95 It's a book which "shows you how"! Illustrates Model HF 610 (6") Response, 60 - 12,000 cps.; Marantz Company 77 actual "set -ups" for the many different appli- rations of tape recorders Read this book bass resonance, 70 cps. $8.95 Mullard Overseas, Ltd. 33 ... before you buy a tape recorder will STENTORIAN TWEETER Model T -10 It Response. save you many dollars ! NO OTHER BOOK 2,000 - 16,000 cps.; power rating, North American Philips Co., Inc. 41 5 watts; 242 lb. Alcomax Magnet System. LIKE IT! No. z In. Illus. Rnh $19.95 179. 150 pages 5% 8% 152 Ortho -Sonic Instruments, Inc. 7S cover $2.95 STENTORIAN CROSSOVER UNITS Correct matching inductances and capacitors HI -FI LOUDSPEAKERS sad ENCLOSURES Pickering & Company 15 for level crossover responses. Input and out- by Abraham B. Cohen put impedances, 15 ohms. Individual Pilot Radio Corp. 37 units THE "CLASSIC" IN HI -FI LITERATURE! for crossover at 500, 1,500 cps... @ $13.95 Presto Turntables Cover 2 or 3,000 cps. (a 59 3.5 Here is a long- needed book. Every question Professional Directory 85 ask about hi- STENTORIAN CONSTANT IMPEDANCE which any hi -fi fan may fidelity BALANCE loudspeakers and enclosures is answered. OR VOLUME CONTROLS and For mid -range, high frequency system bal- Rauland -Borg Corporation 73 This book is supremely authoritative bril- ance. or control of remote Rek -O -Kut Company 6S liantly written ! The author is a recognized au. loudspeakers. rhority- musician -an engineer. Individual units for 4, 8, or 16 ohm im- Rider. John F., Publisher, Inc. 88 pedance. $6.95 ea. Room acoustics are explained and advice is Robins Industries Corp. 85 given . A MUST book for all hi -fi and audio enthusiasts and technicians. For complete literature on these and many other Scott, H. H., Inc. 4 No. 176. 380 pages. 5% r 8'd in. Leather enlvh famous lower priced Stentorian loudspeakers MARCO rover. Hundreds of Illustrations. Only $4.60 Sherwood Electronic Laboratories, Inc. 1 and audio accessories, see your dealer or write: No. 176 -H. Cloth Bound ORIy $5.50 Sonotone Corporation 5 Stereophonic Music Soicety 70 RIDER BOOKS ARE AVAILABLE AT ELECTRONIC Barker Sales Company PARTS DISTRIBUTORS AND IN TECHNICAL BOO( 996.8 Edgewater Avenue, Ridgefield, N. 1., U.S.A. CTORFS IF IIMsVSILsRIF TMFRF 111nFR niRFrT Tandberg 56 Exclusive Sales Agents Tannoy (Canada) Limited 76 JOHN F. RIDER Publisher, Inc. for the U.S.A. and South America Corp. 8 116 W. 14 St., N. Y. 11, N. Y. Charter Member: Inst. of High Fidelity Mfrs., Inc. Triad Transformers In Canada: T /M Whiteley Electrical Radio Company University Loudspeakers, Inc. 64, 65 Charles W. Po=nton, Ltd. 6 Alcina Ave., Toronto, Ontario Circle 88A Circle B8C

88 AUDIO DECEMBER, 1956

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