Ae, Oteepe*Atiotafree

DECEMBER, 1963 60( ae, oteepe*atiotafree www.americanradiohistory.comAmericanRadioHistory.Com EXTRAVAGANCE? Is it an extravagance to silver -plate the critical (often just a few microvolts), is not subject to sig- Radio Frequency circuit (front -end) of an FM tuner? nal losses or the addition of noise. As a result, Scott Scott doesn't think so ... and neither do the ed- tuners can receive many more stations, cleanly, itors of the leading hi -fi magazines. and without distortion. For example ... Audio reporting on the Scott Scott tuners are used in the most critical profes- 4310, said, "Without question, this tuner is one of sional applications. It was a Scott tuner that was the finest extant. It pulled in more stations, loud selected by Bell Laboratories for the famous Telstar and clear, than any other tuner we have tested. The Tests. Mcst broadcasting stations use Scott tuners record now stands at 40 stations.'x for monitoring their own broadcasts and for relay What makes Scott tuners pull in more stations, applicaticns. These professionals recognize the ad- loud and clear, than any other tuners? Is it the ex- vantages of Scott's scrupulous attention to details clusive Scott Time -Switching multiplex circuitry... like the silver -plated front end ... details that make the Scott Wide -Band design? Partly. Scott the ideal choice for enjoying FM stereo in It is also the fact that Scott, and only Scott, goes your home as well. to the extra expense and trouble of silver plating Scott tuners are available in all price ranges, in fac- Radio Frequency circuits. Silver is a far better con- toryassermbled or in kit form. Prices startat$119.95. ductor of electricity than steel or Write today for complete details. aluminum, the materials commonly *Audio, September 1963. used by most tuner manufacturers. With this greater conductivity the - - SCOTT tiny signal received by the tuner H. H. SCOTT, INC., 111 POWDERMILL RD., MAYNARD, MASS. 350 C FM Stereo Tuner $224.95 Prices slightly higher west of Rockies Export: Morhan Exporting Corp., 458 Broadway, New York, N. Y. Canada: Atlas Radio Corp., 50 Wingold Avenue, Toronto. Circle Coy 2 on Reader Service Card www.americanradiohistory.comAmericanRadioHistory.Com DECEMBER, 1963 VOL. 47, No. 12 Number 4 in a series of discussions Successor to RADIO , Est. 1911 by Electro -Voice engineers C. G. MCPROUD Publisher LOUDSPEAKER DAVID SASLAW Editor LOUDNESS AU LIMITS Io JANET M. DURGIN Production Manager JACK BURCHFIELD Chief Engineer Loudspeakers HENRY A. SCHOBER Representatives Contributing Editors We are frequently asked how loudly a specific loud- Business Manager Bill Pattie & Associates, 4161 West Touhy Ave., EDWARD TATNALL CANBY speaker can be played without distortion or danger Lincolnwood 46, Ili. of destruction. This question is not easily answered to home or studio music SANFORD L. CAHN James C. Galloway. JOSEPH GIOVANELLI when asked in regard Advertising Director 6555 Wilshire Blvd., reproduction. Los Angeles 48, Calif. HAROLD LAWRENCE If the material to he reproduced is a simple sine wave, voice coil heating is the normal controlling Warren Birkenhead, Inc., CHESTER SANTON EDGAR E. NEWMAN No. 25, 2- chome, Shiba Hama- factor, and the point where excessive heat (or ex- matsu -cho, can HERMAN BURSTEIN cessive voice coil travel) is reached be simply Circulation Director Altnato-ku, Tokyo. Japan determined. However, steady -state sine waves are not typical of most program material, and this power limit is unrealistic when appli. d to musical reproduction. One outstanding characteristic of musical energy is its transient nature. Even when an orchestra plays Controlling Sound -Reinforcement AUDIO Articles a sustained high level chord with no audible varia- tion, the combined waveform shows markedly fluc- Systems 19 David L. Klepper tuating peak energies. These peaks are formed The Auditioneer 24 John Whitacre when each constantly changing waveform adds to the energy of other waveforms. An Open Baffle Parallel- Series Array 30 R. S. Oakley, Jr. Typically. energy peaks in music will reach a level up to ten times the average or R.M.S. value. The relatively low average level tends to protect the AUDIO Reviews speaker from high heat build -up even at extremely high listening levels. Light Listening 6 Chester Santon In laboratory studies, we have applied up to 100 watts of musical program material to E -V high Jazz and all that 36 Bert Stanleigh fidelity speakers with no apparent distortion and Record Revue Edward Tatnall Canby no signs of immediate failure due to heat or fa- 46 tigue. One fact became quickly evident. The absolute loudness limit for most high fidelity systems AUDIO Profiles lies not with the speaker, but rather with the amplifier. Heathkit Transistor Tester 38 lfode1IM-30 Careful oscilloscope analysis revealed that waveform distortion appeared first at the amplifier Korting "Mozart" Tape Recorder 38 Model 3000 output, usually in the form of clipping. The loudspeaker faithfully reproduced this distorted wave- Fisher FM- Stereo Receiver 44 Model 500 -C form, giving rise to the subjective analysis that the Sherwood FM- Stereo Tuner Model S -3000V speaker was being "overdriven." Substitution of 44 a more powerful amplifier, with greater reserve Shure Stereo Studio Dynetic 59 ilfodel M222 power at the same acoustic output, eliminated the "speaker distortion" completely! The problem of maximum loudness in any system AUDIO in General is further complicated by the growing trend toward speaker systems of medium or low efficiency. If a Audioclinic 2 Joseph Gioranelli speaker system, by design, trades six or eight db of efficiency for other benefits (wider range or Letters 8 smoother response), it necessarily places a heavier Edward Tainall burden on the amplifier to provide a clean signal Audio ETC 10 Canby at high levels. Editor's Review 16 The absolute limitations of any speaker system based on peak performance requirements are very Tape Guide 34 Hernian Burstein difficult to objectively state. Listening tests have proved to have the greatest validity to date, yet About Music 50 Harold Lawrence results vary from listener to listener, and with the New Products 56 frequency and duration of the peaks. A realistic rating for most small speaker systems Cover Story 60 would be in the order of eighty to one hundred watts peak handling power. To realize this poten- Annual Index 66 tial requires an amplifier of forty to fifty watts rating (based on peak performance twice that of Advertising Index 68 the steady -state rating). For technical data on any E -V product, write: ELECTRO- VOICE, INC., Dept. 1233A ,, AUDIO (title registered U. S. Pat. Off.) is published monthly by Radio Mega - zinn, Inc., henry A. Schober, President: C. O. McProud, Secretary. Executive et$C Buchanan, Michigan and Editorial Offices, 204 Front St., Mineola, N. Y. Subscription rates -U. S., a Possessions, Canada, and Mexico, $5.00 for one year, $9.00 for two years; all aher countries $6.00 per year. Single copies 604. Printed in U.S.A. at 10 ot. vlc0overn Ave., Lancaster, Pa. All rights reserved. Entire contente copyrighted o 1 963 by Radio Magazines, Inc. Second Class postage paid at Lancaster, Pa. aa" RADIO MAGAZINES, INC., P. O. Box 629, MINEOLA, N. Y. SETTING NEW STANDARDS IN SOUND Postmaster: Send Form 3579 to AUDIO, P. O. Box 629, Mineola, N. Y. AUDIO DECEMBER, 1963 1 www.americanradiohistory.comAmericanRadioHistory.Com Coming NEXT AUDIO CLINIC Joseph Giovanelli Month make your checks from plate to cathode Send questions to : rather than from plate to ground. Joseph Giovanelli I referred earlier to the use of a signal tracer. There are two types and I use them . 2819 Newkirk Ave. Construction Brooklyn 26. N. Y. both at one time or another. One type of Include stamped. self -addresses tracer is nothing more than amplifier which envelope. is fitted with test leads at its input. These A Ton -and -a quarter of test leads can be placed in the various grid, Sound. Walter Wysoczanski plate, and cathode circuits of an amplifier. describes -mouth As this device is moved from the input to a curved Lower Amplifier Output I output, there should be an increase in concrete horn stereo speaker the Q. Recently I noticed a marked loss of signal output from this tracer amplifier at system he built in his home, volume in my left speaker. I suspe ted my each successive stage. If one stage does not each side of the stereo pair output tubes might be weak. I replced all provide its share of gain or perhaps intro- weighing 1200 four. I still do not have equal vo ¿me in duces a loss, then you will know that this over pounds stage is the one which is defective and must without drivers. each channel. Do I need to replace the remainin tubes be further investigated to determine the Very Low Voltage Relay in my amplifier? Name withheld, Bronx, cause of the malfunction. Remember that a Operation. Ronald L. Ives. New York. cathode follower ; possesses approximately unity gain, so if you connect your tracer 5 e A way of using the -volt A. If your preamplifier is separa from to the output of such a stage, no gain will filament tap on a power the amplifier, do not assume that e dif- be produced over that provided by the pre- ficulty will be found in the amplifi r. Any stage. Further, connecting your transformer, made available check suggested later in this answer should ceding by replacing the rectifier tracer to the plate circuit of such a stage also be applied to the preamplifier. will provide no signal because of the in- tube by a solid -state rectifier, If you have two separate amplifiers in tentional bypassing of this circuit with to power a low- voltage re- the stereo system, it is possible that the large capacitors.

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