studio sound August 1975 25p AND BROADCAST ENGINEERING

not 11,21 be an scussed elsewhere .es and the likelihood ,e had the arrogance to on then becomes a moral

its division into two areas, other is invoked. One is the other words, the problems gh ambient levels. The other _ae likelihood or otherwise that .oss due to high pa levels. Jtected from ourselves: we have to wear .r crash he, ..iid now often have electric concerts limited, J levels in some cases below those found in acoustic ones (for lull dosage discussions, again see elsewhere). In the US, no easy rider would tolerate any such imposition on his freedom. In the UK, attempted suicide used to be a crime, the repeal of that law acknowledging further an individual's own responsibility to himself and to look after himself. On the present less mortal issue, the tendency to choose legislation rather than education does not encourage thought. However, the main concern here is for engineers whose hearing may suffer simply because of their work co ' ions. Funny j.' c about ear defenders too easily mi There 20 commonly agreed interpretation o 24 engineer must take the r`sk wit levels are an essential 40 pedantic German app 46 leave the roo 62 return to the or external. functioning " the battle engineer irrevoca 32 So he H 36 ales engineers and stadio ,ica/ and commercial developments ale without charge to qualified rs, executives and key perso ,ig, broadcasting and cinem ...an buy STUDIO SOUND overseas.

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EDITOR MICHAEL THORNE AUGUST 1975 VOLUME 17 NUMBER 8 ASSISTANT EDITOR FRANK OGDEN EDITORIAL PRODUCTION DRUSILLA DALRYMPLE EXECUTIVE ADVERTISEMENT MANAGER DOUGLAS G. SHUARD ADVERTISEMENT MANAGER TONY NEWMAN MAGAZINE SALES MANAGER DON BAILEY

HEARING damage affects us all in some form or another. Superimposed on typical aging processes appears to be THE LINK HOUSE an GROUP additional factor dependent on exposure, as discussed elsewhere in this issue. The actual extent of the difficulties and the likelihood Editorial and Advertising Offices: LINK HOUSE, DINGWALL of trouble is something on which few have had the arrogance to AVENUE, CROYDON CR9 2TA. Telaphone: 01 -686 2599 pronounce in definite terms. The decision then becomes a moral one. Telex: 947709 The discussion is complicated by its division into two areas, each of which is dragged up if the other is invoked. One is the © Link House Publications Ltd 1975. All rights reserved. issue of industrial hearing damage; in other words, the problems of a sound engineer in unusually high ambient levels. The other is a quite separate issue and is the likelihood or otherwise that CONTENTS people will suffer hearing loss due to high pa levels. In the UK we are protected from ourselves: we have to wear FEATURES our crash helmets and now often have electric concerts limited, to levels in some cases below those found in acoustic ones (for ELSTREE FILM STUDIOS full dosage discussions, again see elsewhere). In the US, no easy By John Dwyer 12 rider would care for any such imposition on his freedom; even if AMBISONICS. PART ONE: GENERAL SYSTEM states are now introducing crash helmet laws and some limits to DESCRIPTION auditorium levels, the latter tend to be more realistic. In the UK, By Peter Fellgett 20 attempted suicide used to be a crime, the repeal of that law AMBISONICS. PART TWO: STUDIO TECHNIQUES acknowledging further an individual's own responsibility to him- By Michael Gerzon 24 self and to look after himself. On the present less mortal issue, SURVEY: HEADPHONES 42 the tendency to choose legislation rather than education does HEARING DAMAGE not encourage thought. By Adrian Hcpe 48 However, the main concern here is for engineers whose hearing may suffer simply because of their work conditions. Funny jokes about ear defenders too easily miss the point. There is no COLUMNS commonly agreed interpretation of the physiology, so any studio NEWS engineer must take the risk with him at his work. High monitoring 16 levels are an essential part of most people's technique. One PATENTS 18 pedantic German approach has been to instruct engineers to AGONY 30 leave the room if the level exceeds a certain threshold. So we WORK 58 return to the dispute as to whether protection should be internal or external. With the industry on both sides of the Atlantic functioning the way it is, there seems little doubt which way REVIEWS the battle will go, such as it is. If that job is done then later the engineer may find himself ACOUSTIC RESEARCH LABORATORY STANDARD to have been at risk, possibly TRANSDUCER irrevocably. The choice is the engineer's, not the physiologist's. By John Fisher 32 So he must know about it. Soon. AMBER MODEL 4550 AUDIO SPECTRUM DISPLAY By Hugh Ford 52

STUDIO SOUND is published on the 14th of the preceding month unless that date falls on a Sunday, when it appears on the Saturday.

DISTRIBUTION CORRESPONDENCE AND ARTICLES STUDIO SOUND, published monthly, enables engineers and studio All STUDIO SOUND correspondence should be sent to the address management to keep abreast new technical and of commercial developments printed on this page. Technical queries should be concise and must in electronic communication. It is available without charge to qualified include a stamped addressed envelope. Matters relating to more than one readers: these being directors, managers, executives and key personnel department should occupy separate sheets of paper or delay will occur actively engaged in the sound recording, broadcasting and cinematograph in replying. industries. Non -qualifying readers can buy STUDIO SOUND at an annual subscription of £4.17 (UK) or £4.20 overseas. BINDERS Loose -leaf binders for annual volumes of STUDIO SOUND are Total average net circulation of 8,535 per issue available from Modern Bookbinders, Chadwick Street, Blackburn, Lancashire. [ABC during 1974. U.K. 5,663, overseas 2,872. Price is £1.25 (UK and overseas). Please quote the volume number or date T. uorc when ordering. O u A..Y Of v..../0n11 J

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www.americanradiohistory.com The recent economic problems of the British film industry, and in particular Elstree studios, have received wide daily coverage. The background to the studio and its record of technical innovation are covered, together with a summary of recent improvements in optical soundtrack techniques with which they have been involved. These include the application of Dolby noise reduction to optical tracks in mono and stereo.

Elstree Film Studios

JOHN DWYER

L A. W. Lumkin (Executive technical Back row : Chris Anderson (2nd assistant dubbing mixer). Front row to R: services), Ray Merrin (1st assistant dubbing mixer), W. Rowe (chief dubbing mixer).

THREE SHORT PARAGRAPHS in EMI's going on; we're building again for shooting in annual report, published last autumn, signalled January.' Nevertheless the report did say . . . another blow to an already reeling British film `We've had some good months this year, we've industry. `Last year,' said Sir Joseph Lockwood, had some bad months. It's happening in every the retiring chairman, `I reported that produc- British business,' and he cited British Leyland. tion capacity at our Elstree studios continued to He thought it encouraging that Orient Express be under -utilised -in common with other UK was now breaking all records. film studios -and that Elstree had made a sub- Alan Sapper, General Secretary of the ACTT stantial loss as a result. In November 1973, as told me shortly after he would be asking for a part of our continuing effort to make Elstree meeting between the Prime Minister and viable, we agreed upon a reduced scale of representatives of the Federation of Film operations with the trade unions concerned. Unions to discuss Elstree's future. They had This resulted in a reduction of our permanent already met Sir Bernard Delfont to protest that manning from 518 to 261 employees. Other they would oppose by all means any closure at economies to reduce overheads were also put Elstree or any reduction in its staff or facilities, into effect. Despite these measures, Elstree's and they would tell the Prime Minister the same position has not improved. The level of film at any future meeting. They clearly did not production is still unsatisfactory, and while we believe Elstree would be in that much financial are continuing to make every effort to put the trouble, bearing in mind the success of Orient studios on a viable basis, we cannot be sure of Express and Confessions of a Window Cleaner its future unless the position improves sub- and asked for all the financial records of the stantially in the coming year.' studios to be made available to them. 'I doubt Elsewhere the report said that only eleven whether they would close it completely because feature films were wholly or partly serviced at it's one of the best technically equipped studios Elstree. Yet the dubbing theatres seemed never in the country,' said Sapper, `and their post - to have been busier -either that or the execu- production facilities are a real money -spinner.' tives at Elstree were masterly when it came to I asked him whether the large acreage at the looking as if they hadn't got a minute to spare. site was a possible reason for EMI's wish to None of them wanted to say much about the make it appear that Elstree was losing money, situation. The then studio manager Freddie and he said he thought it was nothing to do Barbank said last December: `The whole of the with that at all. British film industry has been living from hand Yet when the bad news eventually came the to mouth for years. We've got plenty of work Guardian described it as `sudden'. At the end of 12 STUDIO SOUND, AUGUST 1975

www.americanradiohistory.com January, EMI announced that the staff would Directors, particularly those from America, hold itself in lock to the recorded pulse so, be further reduced from 251 to 48, a reduction felt that the clapper board disturbed artists and without stopping, the whole of the tape could of over 90 per cent within 15 months. Six of the destroyed spontaneity. Another was silent be transferred on to 750 m of 16 mm magnetic studio's nine stages were to be closed. The staff playback, a now familiar system which used an film or, with only one stop, on to two reels of had a mass meeting and the ACTT said they induction loop running round the sound stage to 16 mm film. Elstree say this enabled transfers would fight the closures. Despite their efforts, play music back to actors through a concealed to be done in continuity instead of individual the staff had left by March 27. Freddie Barbank, earpiece. This enabled actors to hear the music ten minute reels of 35 mm after which they had formerly studio operations manager, was and record dialogue at the same time without to stop and reload and then start the machine replaced by former chief engineer John Skinner interference from playback speakers. again. The new system was much cheaper. who was given the title of studio manager. Elstree say they are the only major studio The next development was to use a 12.5 mm Perhaps it is true that what are now regarded equipped with Add -A-Vision, a system devel- four track machine and use tracks one to three as some of the greatest days of movies coin- oped by Livingston Laboratories with advice for dialogue, music and effects and the fourth cided with the Depression. Long before that, and help from Elstree and ABC TV, which was for a synchronising pulse. This enabled pro- in 1913, a young film director named Percy an associate company of Associated British ducers to redub easily, if one hour television Nash had built a studio in Borehamwood. He Picture Corporation Ltd. ABC helped with the shows had to be broken down into half hour had wanted a site on a hill, above the London video side and the Elstree camera and sound shows, by using the separated tracks. Most of fog. He made 90 films there, mainly one reel departments developed the equipment as an this work was being done for ATV's film comedies and three reel dramas. attachment to the Mitchell BNC 35 mm camera. company, ICT, and was networked in the In 1926 an American producer, J D Williams, The system was first used by Gerry Anderson in States on ABC, CBS and NBC. Elstree say they asked Nash where he should build a studio and Slough when he was making those tv puppet have had as many five television shows shooting Nash suggested nearby Elstree. Williams began adventure films in the studio at the same time. building British National Pictures but ran out Add -A-Vision is integrated into the zoom It was inevitable that 16 mm colour film of money before he could finish it so the studios lens. Most of the light goes through on to the would be used for shooting and the man were taken over by John Maxwell, a solicitor film but a small part comes off through a prism responsible, it seems, was television producer who owned a chain of cinemas in Scotland. The into a plumbicon video camera which gives a Monty Berman, who decided that the only way studios were busy, and Alfred Hitchcock made broadcast quality picture of what is going on to to produce a television series economically was the first British talkie, Blackmail, at what was the film. The director, the lighting man, the to shoot in 16 mm. then called British International Pictures. camera operator, the sound mixer and the The studios had been taken over by EMI in Elstree was shut down during the war and continuity girl each have a monitor. The direc- 1969, so the following year Elstree were able used by the army. Rebuilding started in 1946 tor does not need to turn the camera on until to invest in 16 mm equipment worth about £á and the studios were reopened in 1948 as the the shot is right. He need not look through the million. They bought camera equipment and Associated British Picture Corporation. The camera viewfinder and, if someone makes a applied Add -A- Vision to 16 mm cameras. They present executive head of technical services, fluff not normally noticeable until the rushes are also bought additional 16 mm sound recorders, Tony Lumkin, arrived in May that year. There shown, he can see it immediately and cut dubbers and picture projectors for all their were only two sound stages ready: `There was camera. One estimate put it that the equipment recording theatres and review theatres. Elstree no sound building -the bricks and mortar results in a ten per cent saving in shooting time say they are able to handle more tracks for were up but it was a shell.' and so almost a ten per cent saving in production 16 mm dubbing than any other facility in the Lumkin considers that any edge Elstree had costs. The system also keeps people off the country. Now 12 magnetic 16 mm tracks can over other studios from this time on was partly floor-the continuity girl, for example, does be mixed at a time to 16 or 35 mm picture. attributable to their association with Warner not have to keep dashing up to the camera They can record on to 35 mm from 16 mm Brothers, who had had a series of firsts over the operator or the director because she can see tracks, as they do for television, and they can years from The Jazz Singer (1927) through what is being shot on her monitor. transfer from the three 35 mm tracks, recorded colour (1933) and onwards. `Our initial sound These and subsequent developments were on 2000 ft reels of 35 mm, to 12.5 mm tape as installation was jointly planned between our- made to reduce costs. ABC TV were making well as to 16 mm. selves and Warner Brothers so that we inherited telerecordings in the late fifties and involved All the recording areas were equipped with techniques which were not in use in other Elstree in 16 mm work. Elstree say they are the RCA FR10 four track recorders and a bank of studios in England.' only major studio to be involved in 16 mm dual gauge 35 and 16 mm re- recorders from In the early fifties Elstree was one of the first recording. Television series were once shot Magnatech in New York. During the reinvest- studios to change to magnetic recording from entirely in 35 mm but a large end product of ment period they also bought a new sound recording directly on to optical film. Although 16 mm was also required, so they had to trans- console jointly designed by Elstree and Neve. the film industry followed the recording fer the sound not only to 35 mm optical and It has 36 inputs and is capable of eight track industry in using magnetic recording, the magnetic but also to 16 mm optical, and to outputs. Although the desk works mainly as a recording industry was well behind in multi- 16 mm magnetic for foreign versions. multitrack mono desk it has been used for track recording. Even before the change to So Elstree looked for more efficient transfer three track stereo recording. magnetic the studios were using multitrack methods. The solution was to use a 6.25 mm Possibly the most important development, techniques. It wasn't possible to record three Telefunken MIO tape machine. The English however, was that of anticipatory noise reduc- optical tracks on one film so three recorders dialogue version would be recorded on track tion. An optical sound recorder has a mechani- had to be synchronised. They recorded the one, the mixed music and effects (M &E) would cal noise reduction system fitted to it. The orchestra on one, the vocal on another and the be on track two and between them would be sound on a variable area sound track is recorded chorus on another. In the rerecording the an FM pulse system which synchronised the by varying the width of a beam of light which balance between orchestra, vocal and chorus tape to film. They could store one television shines on to the light sensitive film. The beam could be altered. show with both its sound end products on a of light is narrow during low level passages and Similarly in rerecording two optical recorders 75 Am NAB spool of 6.25 mm tape instead of wide during high level passages. On replay a were used simultaneously, one recording the storing it on six rolls of 35 mm magnetic film. light shines back through the sound track on to composite track and one the minus -dialogue The system had two advantages. The first a photocell or solar cell. Without the noise track. When magnetic 35 mm film began to be was that the film rolls could be erased, once reduction system, the black areas on either side used Elstree recorded on three tracks on the they had transferred the end product on 35 mm of the stripe would be wide, so that the photo- same piece of film, as is still done, using one to tape, and then re -used, reducing the studio's cell pickup could read scratches and dust which track each for dialogue, music and effects. investment. In addition, the producer could be would produce noise when the track was Other studios, Lumkin says, were still doing given a credit for the re- usable magnetic film, replayed. Noise reduction acts so that when the composite dubs in English and had to redub reducing the cost to him from around £50 for track is unmodulated a dc bias reduces the for the music and effects track. six rolls of 35 mm film stock to that of around width of the clear area to about 0.08 mm, and During the early fifties Elstree devised a £2.50 for a reel of tape. shutters reduce the width of the dark area, thus number of technological advances. One was a The second advantage derived from the reducing the amount of noise. system called silent turnover, which enables servo -controlled playback function of the The problem with the system is that it takes directors to work without a clapper board. Telefunken machine. This meant that it would 14 13

www.americanradiohistory.com ELSTREE STUDIOS a finite time for the track to re -open and, if a transient arrives, the top of the transient may DIALOGUE MUSIC EFFECTS be clipped, a problem known as low level 16T MASTER TAPE POST `Depending on the type of transient it NAGRA slipping. LIBRARY SYNCED may be objectionable or it may not,' said LOCATION EFFECTS Lumkin. You may hardly hear it but most of the time a trained ear will notice it, particularly POST SYNC REPLAY on dialogue.' Elstree say they have overcome SYNC HEADPHONES 1 the problem by `anticipatory noise reduction'. TRACK 1, They have developed a system which uses two POST SYNC MIX RECORD MIC 161 TO 3T magnetic heads on the transfer machine, one DOLBY DOLBY ENCODE feeding the galvanometer that records the ENCODE sound modulations and the other head, in front the first, feeding the noise reduction amplifier DO BY of ENCODE DOLBY that operated the galvanometer noise reduction ENCODE system. In recent years they have found it much more film only in economical to record on magnetic MAG MAG MAG sls MAG TRIPLE the rerecording theatre at the time of rerecord- FILM wiWi- FILM FILM El TRACK REC ing. The end magnetic recording can then be REC REC REC transferred direct, without further adjustment, on to optical sound negative. They then trans- fer this final magnetic recording, one to one, in the transfer department. The correct transfer o SYNC OR level is adjusted by an accurate 1 kHz tone POST SYNC recorded on the front of each reel of magnetic film. `We have been using it for the last four years with the knowledge that we have no low DOLBY DECODE ú level clipping in our recording.' Anticipatory noise reduction was important,

Tony Lumkin believes, because the Dolby MIXING DESK encoded sound track couldn't have worked, he says, without it. Nevertheless he described as the DUBBING 1 the Dolby encoded optical soundtrack THEATRE 11 DOLBY 'first real improvement in 35 mm optical sound ENCODE to happen in the last thirty years' -pressed to admit that perhaps he might be exaggerating a 3 TRACK little, he stuck to his statement. MASTER The team at Elstree stress that they only 35mm MAGNETIC introduced the Dolby optical soundtrack to the TRIPLE producers after making sure that it was worth- while, technically sound and in the interests of DOLBY good sound reproduction in the cinemas. In the DECODE early sixties they had tried to improve cinema OPTICAL TRANSFER sound by developing a monophonic sound MIX system using magnetic stripes. Elstree's chief dubbing mixer, Bill Rowe, who DOLBY has worked brilliantly (in my opinion) on the ENCODE films as sound tracks for such Steppenwolf, OPTICAL RECORDER That'll Be The Day, Stardust, A Clockwork Orange, Murder on the Orient Express and FINAL SOUNDTRACK many more, explained the reasons why mag- netic sound, which offers three track stereo and a bandwidth of up to 15 kHz, had never caught on: `You have to overcome the economic dis- advantages of getting a good sound, which onwards as had been used for optical tracks. (EMI) cinemas to very good effect. `This means you have to persuade the theatres to 'We made nine movies that way,' said Lumkin. enabled a sound balance to be attained in fairly re -equip to start with. Then when it's in you `The unfortunate thing was that the cinemas short time which would have been impossible have problems with head wear -there's not were not in a state to take it, because when I using subjective methods which had been just one head but a cluster of them and some of went up and down the country visiting our necessary in the past. 'We tried then to line up the heads wear quicker than others-there are theatres I found that in every case I had the theatre to sound like the dubbing theatre in problems of misalignment, theatre managers personally to adjust and set up the equipment which the sound had been made.' A paper des- complain about having to have two sets of to get the correct effect.' He knew that the cribing the system, which applied to normal equipment, one optical and one magnetic, as rest of the industry just wouldn't have accepted optical soundtracks, was published in the well as extra equipment behind the screen for it: `One man couldn't go up and down the SMPTE journal in the late sixties. three, or four track stereo -four sets of ampli- country adjusting all the goddam cinemas. So It was because Tony Lumkin had tried to fiers, preamplifiers and loudspeakers. On top of I gave up the effort until I could get the cinemas improve sound reproduction in the cinemas all that you get problems with oxide dust and in line.' Bill Rowe said that some of the cinemas and found that he didn't have the extra staff head clogging.' Lumkin makes the point that haven't had any maintenance since The Jazz needed to do it that he welcomed the Dolby release prints with magnetic stripes cost 50 to Singer. system when it arrived. It not only improved 60 per cent more than optical release prints. The magnetic track wasn't the end of their the signal to noise ratio and frequency response The Elstree stripe system, however, needed campaign. They also worked on a method of of the soundtrack, both for Dolby equipped only one magnetic head and the same equip- measuring sound output in cinemas, and applied and non -Dolby equipped cinemas, but also ment could be used from the head amplifier it to their dubbing rooms, and to some of their 30 0. 14 STUDIO SOUND, AUGUST 1975

www.americanradiohistory.com A reduction to E é 7.00 for the popular Neumann KM84i has been won, despite inflation, b; continuing demand and increased prodaction. Plus generous disccunts for quantities.

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Pyral tapes range between 20 to 20k Hz. Manu- able for retrospective fixture to the results to mean that 46 % of BASED IN FRANCE, Pyral SA intends factured by ROR Associates of existing desks as well as new ones. Londoners now listen to the com- a sales drive in the professional Ontario, Canada, the ROR 303 Cadac (London) Ltd, 141 Lower bined ilr broadcasts each week recording products market through incorporates a sweep audio fre- Luton Road, Harpenden, Herts within the main listening area, com- the UK subsidiary, Pyral (UK) Ltd. quency generator and receiver AL5 5EL. Phone: 05827- 64351. prising the GLC and immediate Further faith in an expanding locked in sync; the rectified output surrounding areas within the reach market has been demonstrated by operating the y axis of a storage of the vhf transmitters. the establishment of a satellite tape oscilloscope. In addition, an auto - Capital and LBC claim to com- manufacturing plant situated at ranging led digital meter provides mand 23 % of all radio listening Eastbourne, Sussex; this is the first absolute measurement of dBm, time -an increase from the 15 built outside France. To date, dBrn, kHz and percentage total share of audience time reported as capital expenditure in the British harmonic distortion. Accessories Macinnes France recently as October 74. They division exceeds £}M, but by the are available which provide return A NEW PARIS -based company has further claim that the correspond- end of the year this will have loss measurement, remote control been established to handle distribu- ing share for the BBC audience has reached £1M. unattended sweep facility and phase tion of the Amcron range in dropped by 8 %. The present product line includes shift measurement for interchannel France. In addition, the new com- mastering lacquers, magnetic tapes comparison. pany will handle certain other in widths between 6.25 mm and The manufacturers state that the agencies along with their own pro 50 mm, instrumentation and com- analyser finds applications in the ducts. The address for Macinnes puter tapes, and other specialist examination of telephone lines, France is 50 Bis Rue Labrouste, magnetic software. The company data channels, tape recorders and 75015 Paris. Further details are Servo Scully also manufactures a range of other recording systems, equalisers, available from I. M. Marshall, THE LATEST SERIES of 280 machines domestic magnetic tape products. amplifiers and companders. ROR Macinnes Laboratories, Macinnes offer an increased reel size up to Pyral SA, 47 Rue de L'Echat, 94001 Associates Ltd, 21 Rolark Drive, House, Carlton Park Industrial 35.5 cm and dc servo drive of Cretil, France. Phone: 1207 4890. Scarborough, Ontario M1R 257, Estate, Saxmundhanl, Suffolk. capstan. Using a printed armature, Pyral (UK) Ltd, Airport House, Canada. UK agents: Wandel & Phone: 0728 -2262/2615. the new motors are offered as an Purley Way, Croydon CR0 OXZ. Goltermann (UK) Ltd, 40/48 High optional extra on the basic machine. Phone: 01 -681 2833. Street, Acton, London W3. Phone: According to the manufacturer, the 01 -992 6791. increased reel capacity corresponds to a trend towards the use of 76 cm /s for mastering; this requires double the spool capacity for a ATC loudspeakers- addenda given programme length. IN THE SOUND 75 show report (June Tunable band pass filter The basic Scully 280 range com- p16) we stated that the Acoustic prises 280B, 284B 284B -8 INTENDED FOR USE With and noise and Transducer Co is the only British vibration measuring instruments, Change of address offering two track 6.25 mm, four SOUNDCRAFT ELECTRONICS LTD has manufacturer `to produce loud- track 12.5 mm the latest B & K band pass filter and eight track 25 moved from their premises speakers with edge-wound copper offers continuous coverage by cali- former mm width tape format respectively. in Tottenham Court The ribbon voice coils'. Goodmans All models feature brated panel control in five bands Road. motion direction new address is: 4th Loudspeakers inform us that this from 0.2 to 20k Hz. The 1621 Floor, 5/8 Great sensing control, dynamic braking Sutton Street, London is not so; they have been marketing and consists of a tunable single pole EC1. The illuminated pushbutton con- phone no. has also been changed such a drive unit since May 73 and trols. Available in rack or console Butterworth filter, variable band- have subsequently launched width and an integral and is now: 01 -251 3631/2/3. a mounted form, the machines pro- battery further (35 cm) model. Both speak- power supply. vide easy operator control from a ers feature 10 cm dia edge -wound The front panel selector switch remote location. In addition, voice coils, the sensitivity for the allows the bandwidth to be switched optional extras include a vari- 30 cm version quoted as 0.12W for speed system with led readout to 3 % or one -third octave response of 96 dB at one metre. tape measured at the 3 dB drop off actual speed. Scully /Metro- points. The unit can deliver a tech division of the Dictaphone Cadac news Corporation, 475 Ellis Street, control signal to a B & K portable THE COMPANY CONFIRM the appoint- level recorder 2306 enabling the Mountain View, Ca 94040, USA. ment of Frank Woodington as sales Phone: (415) 968 8389. UK agents: chart movement to be synchronised manager. He brings much experi- accurately with the frequency con- Lee Engineering, Ashley House, ence gained from within the broad- Ashley Road, Walton-on- Thames, trol of the filter. B & K Labora- cast and sound recording industry; Didn't they do well? tories Ltd, Cross Lances Road, Surrey KT12 1JE. Phone: Walton - Frank, in his own right, has IN A RECENT jicrar survey conducted on- Thames 28783/4. Hounslow, Middlesex. Phone: engineered sessions at many studios between April 21 and May 4, 01 -570 7774. in this country and abroad. It is figures disclosed indicate a further hoped that the new appointment million Londoners listen to the will relieve Clive Green of much of combined outputs of Capital and his work -load, enabling more time LBC-the London -based indepen- out for design and development. dent radio stations. The last survey, Stellavox in W Germany Cadac have recently announced conducted eight months prior, THE WEST GERMAN agency for Sweep analyser the availability of an automated showed that both stations drew an Stellavox professional, audio and THE INSTRUMENT PROVIDES a real mixdown system for use with their indicated total of 4 475 000 listeners data storage and handling products time graphical sweep of the response consoles. Based on the Allinson compared to the most recent figure has been given to the Akustische of any channel in the frequency Automation design, it will be avail- of 5.5M. The stations interpret und Kino -Gerate GmbH (AKG). 16 STUDIO SOUND, AUGUST 1975

www.americanradiohistory.com In addition, the same company and simple to provide continuous, tion purposes. Pye TVT Ltd, PO England, has begun transmissions will distribute Tannoy professional trouble -free operation without the Box 41, Coldhams Lane, Cam- using the transmitters of the loudspeakers and Lyrec tape recor- maintenance normally expected bridge CBI 3J U. Phone: 0223- Independent Broadcasting Author- ders and cassette tape duplicators. with conventional slider faders. 45115. ity. With an expected coverage of Technical specifications and price Robins -Fairchild, 75 Austin Boule- 320 000 people, the service area lists can be obtained directly from vard, Commack, New York 11725, extends over a 12-mile radius Studiotechnik Retail Sales, AKG, USA. Phone: (516) 543 5200. around the town of Plymouth. 8 Munchen 60, Bodensee Strasse Initially, the programmes start at 226/230, West Germany. Phone: 0600 hours running through until 0 89 -87 00 11. Stellavox, Georges 2200 hours. Plymouth Sound is the eleventh Quellet, Engineer EPZ, 2068 Hau- Ferrograph salesman terive/Ne, Switzerland. Phone: 038 ilr service to open, bringing the TED FARNON HAS been appointed total number of potential listeners 33 42 33. Follow that man as sales manager of the Ferrograph PYE TVT LTD announce the sale of within the specified service area to Professional Recorder Co. He over 20M people. There were three an ob vehicle to the Egyptian joins them after ten years' experi- broadcast network specifically 'to applications for the station fran- ence with RCA selling broadcast chise, the successful consortium perform a unique function follow- equipment to radio and tv stations. ing the movements of President being headed by The Earl of Ted will assist marketing manager Morley, chairman of Plymouth Coffee pot Sadat for both on the move and Paul Heelas in the sales and promo- Sound Ltd. THE ADVANTAGES OF a sealed rotary on location live broadcasting and tion of the new Studio 8 profes- attenuator and the convenience of recording'. sional tape recorder. The Ferro - a slider are claimed to be combined Powered from a local mains graph Company Ltd, Auriema within the 'Rotary Slider' produced supply if available, the ob truck House, 442 Bath Road, Cippen- by Robins -Fairchild. Officially can operate off its own batteries ham, Slough, Bucks SL1 6BB. described as 'coffee proof', the for up to three hours before re- Phone: 062 -86 62511. units feature two separate resistive connection becomes necessary. The radio tele- elements driven by a common vehicle is fitted with vhf THE DICTAPHONE CORPORATION, slider arrangement. The makers phone to provide cueing from the parent company of Scully- Metro- state that the mechanism is rugged base station for programme direc- tech, have begun a 'cost- reduction program'. Part of the reason, we understand, apart from the usual Synthi follower 'cash flow' difficulty, is that sales have fallen. Thus it seems strange Left: The ROR 300 audio sweep THE LATEST BLACK box from Omni - analyser available from phon offers pitch and envelope that they should sack John Didlock, Wardel & Goltermann control of internal generation and who in 1973 was the division's best processing by reference to the pitch salesman, having achieved 125 per and shape of an externally applied cent of the sales target he was given audio signal. This can be derived that year, for which he was from either mic, electromusical rewarded with a trip to Hawaii for source or another synthesiser. himself and his wife. In operation, the Metamorpho- A matter of weeks ago, Dicta- to take ser translates the input control phone failed in an attempt audio voltage into control voltages over an American dental supplier had proportional to the lowest pitch, called Sterndent. Sterndent Below: A new speaker from been resisting bids by the American Technics. The SB 7000P level and timing. These are applied to conventional synthesiser func- company Cable Funding, and described as a linear phase Dictaphone agreed to pay $19 in loudspeaker. tions to produce new sounds which for each of the 2.1 million bear a limited relationship to the cash original audio signal input. The outstanding shares in Sterndent, to the Financial Times of basic functions incorporated within according 26 this year. If it had been the unit include a pitch follower, February the have envelope follower, noise generator, successful, bid would pass filter and amp- doubled the size of Dictaphone; multiplier, low the litude shaper. one of the reasons for making the large cash value of the The manufacturers suggest appli- bid was for voice and precious metals held by Sterndent. cations in synthesis couldn't instrument accompaniment, incor- In the event, Dictaphone fund the takeover. poration at mix -down stage to lay It's even been reported that MCI new tracks from existing ones, were visited by Scully emissaries pseudo frequency shifting (offset to interested in taking over MCI, this the pitch generator) as well as many a time when Scully don't have others. The basic unit costs $920 at a flying sales representative in from Omniphon, Box 166, Church- Europe or North Africa. In ill Road, Mason, New Hampshire October last year Dictaphone were, 03048, USA. themselves, the object of a take- over bid by the Northern Electric Company of Canada. Dictaphone filed a lawsuit to fight the $12 a share offer, accusing NEC of 'fraud'. Didlock's disappearance has not Latest ilr station changed the Scully dealerships, PLYMOUTH SOUND, the first local and their equipment is still available radio station in the south -west of from Lee Engineering. 17

www.americanradiohistory.com monies

THE FOLLOWING list of Complete Specifica- Support plate assemblies for electret trans- Phase comparator circuits. tions Accepted is quoted from the weekly ducers. 1399433 Nihon Denshi KK Officia! Journal (Patents). Copies of specifica- 1398237 Cambridge Consultants Ltd Apparatus for recording and reproducing tions may be purchased (25p) from The Patent Liquid crystal display means picture signals and a medium for carrying said Office, Orpington, Kent BR5 3RD. 1398262 EMI Ltd picture signals. Aerials. 1399464 EMI Ltd 1398318 Electonique Marcel Dassault Sa Methods of shaping styli. Radio signal receivers. 1399511 Matsushita Electric Industrial Co May 7 1398330 British Broadcasting Corporation Ltd 1397662 Siemens AG Acoustics of studios and the like. Quadraphonic devices. Electroacoustic transducers. 1399512 Martin Marietta Corporation 1397668 Singer Co May 14 Method and circuit for timing signal derivation Digital tone generator. 1398607 Soc Italiana Telecomunicazioni from received data. 1397755 Philips Electronic & Associated Siemens Spa 1399525 Rank Organisation Ltd Industries Ltd Speech interpolation system for time -division Record playing machine. Synchronisation of a radio signal receiver. multiplexed signals. 1399534 Pioneer Electronic Corporation 1397758 Siemens -Albis AG 1398614 Froidevaux A Automatic cassette changing mechanism for a Telecommunications exchange systems. Sound recording methods and apparatus. tape recorder or reproducer. 1397759 Siemens -Albis AG 1398647 Motorola Inc 1399559 Synaps Co Ltd, and Yamamoto, H Pcm telecommunications exchange systems. Sequential tone signalling system. Method of and apparatus for reproducing a 1397760 Siemens -Albis AG 1398665 Suzuki, T gramophone record. Pcm tdm telecommunication network systems. Magnetic head height changing device. 1399766 Motorola Inc 1397828 International Business Machines 1398689 Ted Bildplatten AG AEG -Telefunken Acoustic transducer including piezo -electric Corporation Teldec driving element. Current generator. Method of and device for producing a readable 1399781 International Standard Electric Cor- 1397856 Oak Industries Inc. identification mark in the central area of a poration Converter. disc- shaped information carrier particularly in Headset. 1397900 Sansui Electric Co Ltd a first stage for an audio disc. 1399819 Marconi Instruments Ltd Encoding method for converting multichannel 1398732 Sony Corporation Ramp voltage generators. sound signals into two -channel composite Signal processing system. 1399844 Coal Industry (Patents) Ltd signals. 1398733 Sony Corporation Radiating transmission lines. 1397972 Blaupunkt -Werke GMBH Variable filter. 1399846 AKG Akustische U Kino -Gerate Magnetic tape machine. 1398786 Sony Corporation GmBh 1397973 Kokusai Denshin Denwa Co Ltd Multisignal transmission apparatus. Artificial reverberation device. and Post Office 1399179 Nippon Gakki Seizo KK 1399950 Bosch Fernsehanlagen GMBH, Time division multiple access satellite com- Electronic musical instrument capable of Robert munications system having special reference providing a third type of musical tones by Television apparatus. bursts. operation of two keyboards in addition to the 1399961 Asahi Glass Co Ltd 1398152 Fuji Xerox Co Ltd ordinary melody and chord tones. Method of forming a patterned transparent Circuitry for reducing the bandwidth of an electro- conductive film on a substrate. information signal. May 21 1399980 Okikiolu, G O (trading as Okikiolu 1398171 Industrial Research Products Inc 1399365 Boeing Co Scientific & Industrial Organisation) Diaphragm assemblies for electret transducers. Apparatus for coding audio signals. Scanning systems employing electromagnetic 1398172 Industrial Research Products Inc 1399393 Sony Corporation wave energy.

DECCA LTD, IN two new patents (BP1373511 on the thin thermoplastic layer which separates generally conventional manner for production and BP1373512) describes an interesting new it from the conducted disc. Especially if the runs of disc copies. The claim is that discs approach to the production of gramophone thermoplastic is heat -softened, it will deform produced this way will have a band width records. Although the patents are concerned in direct relation to the strength of the charge, capability of up to 50 MHz. The pressed discs mainly with the manufacture of video discs, to produce a groove modulated in hill and dale can be played back either with conventional they do contain clear statements to the effect fashion. styli or other forms of pressure transducer. that the claimed technique is applicable to The master thus produced is of course Probably the technique is already in use as conventional gramophone records for playing unplayable, but if it is coated with a thin layer part of the Teldec video disc system, but the with conventional pickups. of metal by evaporation techniques, it can be hint that records made in this way can be The technique described relies on cutting a played back for checking by rotating it under reproduced on semi -conventional gramophones groove in a disc blank with a modulated an electron gun and picking up the electrons does suggest that Decca has thoughts, however electron probe. The disc blank is formed of a scattered from the groove. Pickup is via an vague, of producing wide band width audio conductive metal, coated with a thin layer of electron collector. The output from the discs. Of course with band widths of the order thermoplastic. This disc is rotated on a turn- collector is a signal which varies as the groove claimed it becomes possible to record large table beneath an electron probe and the depth varies in wavelike motion to give an numbers of discrete sound channels in a single electron beam is modulated by the signal to be accurate reproduction of the original recorded groove. recorded. Thus as the disc rotates there is laid signal. Adrian Hope down on its surface a spiral track of varying Decca suggests that the metal- coated master electrical charge. This charge creates a force can be used to grow mothers and stampers in 56 *- 18 STUDIO SOUND, AUGUST 1975

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www.americanradiohistory.com -reproduction is per- Ambisonics is a technology for Ambisonics in the perspective of satisfactory surround designed -sound which aims surround -sound technology fectly practicable in a system surround from the start to use two available at not making four specifically MONOPHONIC REPRODUCTION pro- channels. (or any other number) of vided information about direction and distance 4. Independent access to the signals reaching loudspeakers audible as separate only implicitly, through ambience labelling. each loudspeaker appears at first sight to sources of sound. It is Stereo added explicit directional information give the producer or recording engineer designed using appropriate over a front -sector not exceeding 60° in width maximum freedom, but in fact denies it engineering methods and (ie L30 °, although some discriminating listen- to him because it presents him with a psycho- acoustic theory that has ers prefer to set the limit for really satisfactory problem analogous to opening a lock shown good predictive stereo -blending at ±15 °). without having the key. Except in the can special case of an image in the direction value to make best use of Beyond stereo, the technology be and at the distance of one loudspeaker it channels of developed in several ways: available loudspeakers. does not suffice simply to squirt indepen- more), 1. By using more communication (two or 2. By using more channels of communication. dent sounds from each speaker. In general and of loudspeakers (a 3. Making better use of the available number each loudspeaker should radiate a wave limitation'often forgotten), to of loudspeakers and channels. of amplitude and phase carefully calcula- give stable and 4. Extending directional information from ted to combine in the listening -space so as uncoloured acoustic images in the 60° front -sector of stereo to a full 360° to reconstruct a simulacrum of the intended any position, keeping the surrounding the listener in the horizontal surround -field fulfilling relevant psycho- physical means of reproducing plane, or to complete spherical surround acoustic criteria.' This reconstruction is to an acoustic the sound as reproduction including height. in some ways analogous ways are distinct, but of course the great- hologram, and account must be taken of unobtrusive as possible. It claims These est opportunities for enhanced capability lie in the size and shape (unknowable at the wide freedom of combining them as an integrated whole. In time of recording) of the individual recording methods and of source general terms, this is the aim of the NRDC listener's loudspeaker array. material, as well as protection Ambisonic technology. A competent system takes care of these of recorded material from In ordinary life we are bathed in sound from precise interrelations automatically, just obsolescence. all directions; so much do we take this for as a key automatically brings the levers granted that it often passes unnoticed until it of a lock into register so that the bolt can is cut off, eg in an anechoic chamber, when its slide freely. Unless the system does this, loss is keenly felt. Except in so far as the there is virtually no chance of achieving reverberation of the listening -room can supply clean stable images other than in a the deficiency, stereo reproduction subjects us restricted set of directions. The result is Ambisonics. to this deprivation. A major aim of develop- the familiar practical restriction of ments beyond stereo has therefore rightly been `quadraphonic' reproduction to corner the extension to surround -sound reproduction. positions, front sector, and perhaps rear The first attempts at surround -sound (apart centre, with side positions virtually Part one: from some early experiments) used an approach unusable (see illustration). generally called `quadraphonic'. This term has A particularly unfortunate form of the not of course been precisely defined, and usage quadrifontal approach, which may perhaps be `general system is not always consistent. We shall therefore called the `full quadrifontal' form, assumes in use, as a label for this general approach, the addition that the four source -signals are pair - more accurate term quadrifontal, meaning wise blended. This imposes further restrictions `four- source'. This will be taken to mean that and disadvantages: description there are assumed to be just four signal sources 1. It makes less than full use of the informa- which are to be connected to exactly four tion capacity of the available channels; it loudspeakers in a one -to -one manner through is possible to do as well or better with less four respective channels. than four channels. Based on existing practice relating to four 2. The implied directional coding, having PETER FELLGETT* track master tape, and on the probability that discontinuities of slope, cannot be realised most surround -sound listeners will (at least at by pick -up from any combination of first) be constrained by the size of their pockets ordinary directional microphones. Natural and the shape of their rooms to use four sound, including its indirect reverberant loudspeakers, these assumptions have a content, is therefore excluded. superficial plausibility, but further considera- 3. The format gives poor results when tion suggests them to be inadequate in several replayed directly through four loud- important ways: speakers (see Part Two). It is therefore 1. Four track master tape is by no means the particularly inappropriate to take this only source of signals to be considered: unsatisfactory form of playback as the there is multitrack and multi-microphone standard of comparison for surround - material available for surround pan- sound. potting, and of course the natural sound- 4. It places undesirable restrictions on the field of performed music including rever- encoding loci that can be realised subse- berant as well as direct sound. quently, particularly in two channel 2. There are very good reasons (see Part format; for example the Japanese `Regular Two) for not being restricted for ever to Matrix' definitions2 cannot be implemen- some fixed number of loudspeakers, ted by matrixing pairwise blended material. especially not to four. This (and other) criticisms of this widely - 3. The assumed objective can be attained used four track format were at first only if four channels are available, and strongly resisted (using blanket 'commer- in their absence can only be imitated cial' assertions) but are now recognised more or less unsatisfactorily. This require- even in the so- called ` pairwise' and ment precludes the direct use of the many `optimum' loci incorporated in the pro- visional `matrix quadraphonic' standards "Professor of :Cybernetics and Instrument Physics, two -channel recording or broadcasting University of :Reading media at present used for stereo, whereas of the USA RIAA.° 20 STUDIO SOUND, AUGUST 1975

www.americanradiohistory.com om+ Producer IAN COTTERELL CARDT (b) Multitrack and multi- microphone RAM, (A BBC Transcription Services 1 Próducer soma her, ENO recording) # Shela. material for pan -potting; that is to I 1.5 am Closedown 9.0 News softly Prods say, mono signals on which synthetic cuas directionality is to be Radio 3 Stereo imposed. There 11.e is never, of course, any difficulty in

I 1!IhlNlll111116111GIN1,! R principle in building pan pots to ti 11.5 >, 4 < conform VHF rx Any to any encoding standard Aerial Front (Deta whatsoever in any system. The more Right 11.50 demanding requirement is for a means of adding artificial reverberation !RES. Aerial 12.( having subjectively smooth and un- The .speakers Splitter 12.2 coloured characteristics. (In the form a square You present state of technology artificial and listeners sit Radio 4 Stereo : Prese: ambience, as distinct from mere at its centre See th reverberation, is best obtained natur- H. Back Feel Back ally, if this paradoxical St Right NANCY' way of putting Left ppeoplt it can be excused.) mas h ave Living quad in your sitting rooms With (c) Existing pairwise-blended material. .. Listen to The First Nowell: 12.0 tern b This should be seen as a rescue operation RADIO TIMES DATED 19/28 DECEMBER 1974 for historical material, RADIO TIMES DATED 19/26 DECEMBER 1974 optimising the compromises insepar- Above: An illustration of the restrictive limitations of the four-source 'quadrifontal' approach able from the limitations (discussed to surround- sound. in the opening section) inherent in this format, which should therefore The basic fault of pairwise blending is that system. Its methods conform to established not be used for new recordings where alternatives are available. each musical instrument (or other source) principles of sound engineering, applied in new This is considered by itself activates only one pair of ways and making use of newly acquired nevertheless an important requirement in view of the large investment channels or loudspeakers. This is not beyond knowledge of psychoacoustics. It is not of of the stereo in concept or capability, but merely course perfect, since perfection would require industry in material recorded in this form. extends stereo to less and less suitable speaker- many thousands of channels and a million or angles and hearing sectors as we go from front, so loudspeakers. 2. Availability of a format, for studio use, robust to the inevitable small errors of to back, and to the sides. Requirements for a surround -sound Quadrifontal assumptions underlie the system intermediate recording and providing good regrettable practice of using `four channel' (or Necessary or desirable requirements in a facilities for processing, including a versa- even `quad') as if it were a synonym for viable surround -sound system include the tile gamut of `effects'. This format should surround sound. Two channel surround following: above all preserve explicit directional systems are then called `matrixed four -channel', 1. Ability to accept any competent source information, and thus preserve options for creating the need to distinguish systems that material. This includes at least: the future. do actually use four channels as `discrete four - (a) Natural sound -fields. This is import- 3. Encoding standards, for public issue, channel' (although the channels are in fact ant for all kinds of performed music, having at least the following properties: (a) Unambiguous continuous, blended and frequently multi- and must include reverberant as well encoding of every plexed!); we eschew such misleading terms. as direct sound. It does not suffice to possible sound -direction. Any reference to `the original four -track tape' provide merely a vague splash of (b) Low sensitivity to errors of transmis- lies of course entirely within quadrifontal reverberation having an appropriate sion and of decoding. (c) assumptions; in reality the original to be decay time. There should be a Freedom for the listener to decode reproduced is nothing else than the producer's structured association of direction and into any reasonable number of loud- or recording engineer's intentions, and any delay of indirect sound giving specific speakers in any reasonable array. In intermediate format is to be adjudged good or information about the acoustic ambi- particular, rectangular speaker arrays bad according as it helps or hinders the realisa- ence of the performance, including should be catered for, since few rooms tion of this original. definite impressions about the size and are square. The desirability of not Against this background, Ambisonics may shape of the hall. Recent research has restricting the number of loudspeakers be seen as a basically straightforward tech- shown that ambience labelling accord- to the conventional four has already nology for surround -sound reproduction, ing to place of origin of each sound is been indicated, and is further discus- designed from the beginning to accept all an important aid both to image sed in Part Two. competent source material, and to make the localisation and to the ability to (d) Capable of being decoded so as to best use of the available resources in channels discern inner lines in a musical texture give accurate and stable localisation, (two or more) and loudspeakers (any reason- despite differences of intensity level. and freedom from coloration, accord- able number), neither seeking to reproduce a Balance is thus made less critical and ing to the best available psycho- derived `original' nor attempting or pretending (particularly in pop) greater musical acoustic criteria. to communicate more channels -worth of complexity becomes acceptable by a 4. Mono and stereo compatibility. In one information than there are channels in the given audience. sense, this is a special case of the listener's freedom (as in 3(c)) to use any number of loudspeakers, ie one for mono and two for stereo. The special difficulty is that FIG. 1 BASIC SIGNAL PATH IN AMBISONIC SURROUND SYSTEM mono and stereo represent methods of decoding (representable indeed by matri- ces) prescribed by useage, which are none- theless definite for being trivial in the TRANSDUCER sense of requiring no explicit decoder but (SOUND-FIELD STORAGE OR DECODER LOUDSPEAKER

MICROPHONE) TRANSMISSIOH (ADAPTABLE TO ARRAY IN only suitably connected pieces of wire. ENCODER OR DIRECTION MEDIUM LOUDSPEAKER -3 matri- SOURCE LISTENING Unfortunately the implied decoding 'RECONSTRUCTED' SYNTHESISER 12,3, ETC. CHANNELS) ARRAY) ROOM ces (`obvious' though they seem) can be SOUND FIELD (PAN -POT) shown to be incompatible in any context of two channel surround sound encoding. 220- 21

www.americanradiohistory.com AMBISONICS -PART ONE FIG.2 This is not the 'fault' of any surround sound system (not even quadrifontal) but

is the result of an unhappy historical SOUND - A LIVE AB accident. Some compromise therefore has -FIELD PERFORMANCE MODULE stereo MICROPHONE to be made between mono and MONO compatibility in any two channel surround STEERING OF The available means of effecting TO CONVENTIONAL system. "VIRTUAL PROCESSING this compromise are fortunately sufficient MICROPHONE - ( to reduce the technological incompatibility STEREO

to the level of the inevitable artistic com- OPTIONAL e promises between mono and stereo; they RECORDING need not affect the surround reproduction ITETRAPHONIC) characteristics, essentially because the choice of surround decoder is still open at the design stage. 5. Capability of growth to give protection RECORDING PUBLIC ISSUE against obsolescence. Primary interest 4-TRACK OR I MONO -AND MASTER TAPE CORRECTION be (and probably is) in two channel MIXING ENCODING TRANSMISSION should STEREO IPAIRWISE UNIT (2,3 ETC systems, because of the extensive ready - COMPATIBLE) STEREO.BLENDEDI CHANNELS) made commercial outlets available in two channel media of recording and broadcast- ing originally developed for stereo use. It is important however for the two channel technology to be compatible with exten- AMOISONIC MONOSOURCES AMBISOHIC sions into more channels as they come into ARTIFICIAL I MULTI-TRACK PAN -ANO -TILT REVERBERATION they will, MULTI-MICROPHONE POTENTIOMETERS wider use (as without doubt UNIT sooner or later), eg three channel fm ETC) broadcasting making full use of the triple audio bandwidth of the Zenith -GE system, multiplexed vinyl discs, multi- track magnetic tape, and the use of video- disc technology. As soon as at least three the possibility channels become available, listener's loudspeakers; suitable options phones to be simulated and their directions including height information has to be of and adjustments are provided in Ambi- steered (including vertically) after the considered. even only as a contingency if sonic decoders. recording session. Although remote real - for when the public may be ready for it. It is hoped shortly to release a set of Reports* time adjustment of directionality has long important to hold It is particularly giving details and specifications, which the been available, for example in the AKG master -tapes in a format that will not be present article is of course too small to contain. C24 microphone, post -session freedom of prejudiced by such developments in the To the best of our knowledge the NRDC adjustment is believed to be new. In foreseeable future. Ambisonic system alone fulfils some of the addition the virtual microphones are truly individual requirements previously set out, and coincident (see Part Two), a requirement Ambisonic systems and characteristics is almost certainly unique in fulfilling all of of conventional stereo hitherto unfulfilled. The basic NRDC Ambisonic realisation is a them. (It is worth noting that the sound -field two -channel pantophonic system, ie giving 360' The basic features of an Ambisonic surround- microphone depends on placing capsules horizontal surround and needing only stereo reproduction chain are displayed in fig. 2, in accordance with Sampling Theory on a recording or broadcasting media for dissemina- together with some of the facilities that can be sphere, and the associated circuits are an tion. It is extendable to three channel panto - provided. The following aspects may be integral part of it; the superficial resem- phony, and to three or four channel periphony particularly noted: blance of the lowest -order form to the (ie with height). Particular attention has been 1 Sound -field microphone. This is an omni- well -known tetrahedral array of separate given to the use of a third channel of reduced directional microphone in the true sense, microphones is mainly misleading.) bandwidth (as in the Nippon Columbia TMX which is the opposite of non -directional; it 2. The choice of a C- format encoding stand- system). Five channel pantophony and nine characterises in a symmetrical manner the ard is central to the whole design. It must channel periphony have also been studied waveform and directionality of sound be mathematically compatible at the two theoretically; although these are not of current arriving from any direction (including interfaces respectively to the source - commercial interest, it is reassuring to know vertical components). In its present first - material and to the listener's equipment that compatible developments are possible well order implementation it does so in terms so as to be capable of correct decoding. beyond presently foreseeable needs. All of four signals corresponding to the A basic tool for design and characterisa- systems share a uniform technological design, spherical harmonic of directionality of tion of two- channel encoding is the which includes the following essential steps order zero, and the three of order unity. Poincaré- Stokes sphere, first used in this and signal formats: Recordings of these signals (or their connection by Scheibers and much 1. Transduction or synthesis of signals equivalent), especially in B- format, are developed by Gerzon.3 Like a circuit representing both the desired sound wave- called tetraphonic (there is of course no diagram, it gives a geometrical picture form and its directionality. A signal correspondence with the four signals from which system properties may be format directly related to cardinal direc- assumed in quadrifontics). An important inferred (including the weaknesses of tions has been standardised as A-format. by- product of recording in tetraphonic systems claimed to be 'quadraphonic'). 2. Conversion, where a separate step is mode is that the complete capture of first - It is now known that for surround - required, into studio and recording order directional information enables any reproduction the horizontal pan -locus on B-format. combination of non -directional, figure-of- the Poincaré- Stokes sphere should be 3. Encoding for public dissemination; this eight, cardioid or hypercardioid micro- nearly a great- circle. The Nippon Colum- coded form is defined as C-format. bia BMX system uses a great -circle locus, 4. Decoding into signals suitable for driving Enquiries can be made Attn. P. Thompson Esq, and a different one is defined by the loudspeakers. This D format cannot be National Research Development Corporation, PO Japanese RM specifications. The Ambi- precisely standardised since it necessarily Box 236, Kingsgate House, 66/74 Victoria Street, depends on the number and layout of the London SW1 E 6SL. 40 22 STUDIO SOUND, AUGUST 1975

www.americanradiohistory.com Anything BASF anywhere in the country; in 4S hours. Guaranteed. One of life's little ironies, it seems, is than, And they even offer special prices to pro- the best is invariably the least accessible. fessionals, studio people and freelance recordists. So it was with BASF's professional range Into every life, a little sun must fall. of tapes and tape accessories. The more specialist items have always At last. Now tell me some of those low prices. been hard to come by - especially for small orders. But now there's a new deal for professional Name Company sound people, from BASF and Audio Products. Address Audio Products stock everything BASF produce in tapes, right down to Profi -NAB adaptors, calibration tapes and the weirdest-sized spools. SS2 They'll service any order (by van in central London) in just 48 hours. AUDIO PRODUCTS Even if it's only worth a fiver. Audio Products,16 Grosvenor Place, London SW1.Te1:01- 2352537.

www.americanradiohistory.com Conventional methods of The main aim in the development of NRDC phone clusters use microphones with poorly 'quadraphonic' reproduction may not ambisonics technology has been to record, to defined polar diagrams that are frequency- convey the original sound field to convey to the consumer, and to reproduce an dependent and spaced apart, and so fail to reasonable encoding best advantage. The studio accurate and repeatable surround sound direc- satisfy a specification. tional effect. It is now well known, both from Conventional mastertape encoding assigns the techniques for ambisonics and its controlled experiments and from the experience four speaker feed signals to four tracks of a applications are discussed, in the of recording engineers and producers, that tape, but it is obvious that this is a sub -optimal light of both accepted 'quadraphonic' existing surround sound approaches (including procedure, even with correctly designed micro- techniques, and the requirements of the four channel 'discrete' approach) give phones and panpots. In order to recreate the further accurate reproduction of extremely poor image stability for all positions illusion of a given directional field, it is obvious the sound field. Areas of except the four corners, even under ideal con- that the speaker feed signals will not be the compatibility and of disparity are ditions. With 'discrete' techniques, the front same for a rectangular speaker layout as for a discussed, to be read in the light of stage suffers from the 'hole in the middle' effect, square one. Thus if we are to accommodate a Peter Fellgett's system description and the sides are virtually unusable in any less - variety of shapes of speaker layout appropriate than -ideal situation (eg when the listener is not to differently shaped listening rooms, we need to on page 20. at the centre of the speaker layout, or when the use a decoder to derive the speaker feed signals layout is non -square). appropriate to the layout used. The impracticality of existing approaches has As we shall illustrate later in this article, the led to a careful study of each stage of the multi- optimal decoder even for a square speaker lay- channel recording and reproduction of a sound out is a rather complex frequency -dependent i Ambisonics. field. 2 3 *. The aim of a surround sound matrix, and so we must face the fact that the system is to reproduce at the listener's ear mastertape merely encodes the sound field accurately, reliably and repeatably, the direc- information, and not speaker feed signals. Part two: tional sound field created in the studio either Studies' in the design of decoders for four- by a sound field encoding microphone array, 1 speaker rectangle layouts show that three or by artificial directionality encoding devices channels of information are optimal for accurate Studio (pan -pots) or artificial surround -reverberation image localisation. The addition of a fourth devices. This aim contrasts with the aim2 of channel always degrades image localisation techniques quadraphonic systems, which is to duplicate quality (eg by giving a 'hole in the middle' in the home the defects of a pair-wise mixed effect). Thus, the basic horizontal encoding matertape. Without accuracy and repeatability specification has to be three -channel. Most MICHAEL GERZON* of directional effect, the recording producer's studio equipment used for surround sound work will not be heard correctly by the domestic mastering has four available channels, and so listener, and artistic communication will be the problem arises of how to use this fourth compromised. channel. Since no useful extra horizontal infor- In order to maintain accuracy of effect, the mation may be encoded in the fourth channel, process of encoding the sound field on to a it may most fruitfully be used for encoding mastertape must be accurately specified, and height or elevation information. the specification accurately followed in either It is not suggested that periphonic (ie with- the microphone arrays or the pan pots. Exist - height) reproduction will be a serious com- ing 'pairwise' pan pots do not give a satisfactory mercial proposition at the present time, but encoding specification'. Similarly, most micro- periphonic technology is now understood, and

FIG. 1 AB MODULE ALL RESISTORS SHOULD HAVE AN IDENTICAL VALUE, SAY 330

If --Mti--III INPUTS

.----V.A.,..----

RB

M/,

*Mathematical Institute, University of Oxford 24 STUDIO SOUND, AUGUST 1975

www.americanradiohistory.com The important thing about AB modules is nais is to use a panpot. Fig. 3 shows a circuit of FIG. 2 ARRANGEMENT OF CAPSULES IN that exactly the same circuit converts back from a panpot (feeding a virtual earth mixing stage) SOUND FIELD MICROPHONE B- format to A- format. Thus, if one puts X, that uses a joystick control to meet accurately (VIEW FROM FRONT -NOT TO SCALE) W, Y, Z into their respective inputs, LB, LF, RF, the encoding specification for B- format for RB comes out. If one feeds a conventional horizontal sounds (so that the Z signal is zero). 'discrete' or pairwise mixed signal into an AB The `X -pot' and Y -pot' of fig. 3 are the potenti- module and the discards the Z output, then the ometers that respond to the 'up -down' and X, W, Y signals are correctly encoded B- format 'left-right' motions respectively of the joystick signals for the four corner positions, with slight (see fig. 4). For correct results it is vital that the deviations from the correct encoding elsewhere. travel of the joystick be restricted by a mask or (This deviation is one of the causes of conven- cut -out to that range of X -pot and Y-pot resist- tional discrete reproduction giving poor non- ances in fig. 4 such that x2 + y2 1. In other corner images -the B- format signal will not words, the corner travel must be restricted to make this defect worse). -1 -0.707 of the way from the centre to the end There are two main ways of producing correct of the pot tracks, although the full range of each B- format signals. The first is the Calrec sound pot may be covered when the other is centred. field microphone (which is still undergoing It is also possible to convert existing pairwise evaluation and development). This has been pan pots to give optimal ambisonic encoding. developed by the present writer for the NRDC This is clearly a worthwhile option for use with and uses (see fig. 2) a tetrahedral array of existing equipment. The modifications involve cardioids to feed a frequency -dependent matrix fitting a mask to the joystick control to limit circuit. The matrix circuit fulfils the dual func- 26

not much more complex than horizontal -only FIG. 3 HORIZONTAL PAN POT technology. The adoption of a periphonic standard at this stage will prevent the premature obsolescence of valuable mastertapes in ten or fifteen years when periphony becomes commer- A meanwhile will permit producers to MONO cial, and INPUT gain periphonic experience without premature +7R- commercial pressures. It is also wise to ensure nnn that existing media can change over smoothly X -POT to a periphonic standard in the future, so as to 0.707 R prevent a repetition of the chaos caused by quadraphonics. At the present time, the height information gives useful additional mixdown 0.707R flexibility for stereo or horizontal surround effect. If height is not required, it may be omitted, as in most of the equipment described 7R _ subsequently. For studio use, there are two four channel A- format and B- format. signal formats, termed 0.707R A- format consists of four channels LB, LF, RF, RB compatible with existing 'discrete' practice for the four corner positions. Technically, the 0.707R A- format signals may be described for horizon- VIRTUAL EARTH MIXING STAGE tal only sounds as the outputs of four hyper - cardioids each having nulls 120° off-axis (or their panpot equivalent signals) pointing in the four corner directions. When height is included the A- format signals are the outputs of four Lion of converting to B- format and of providing hypercardiods with nulls 114.1° off axis point- FIG. JOYSTICK CONTROL ACTIVATING electronic compensation for the spacing of the 4 ing respectively 35.3° below, above, below and X -POT' AND Y-POT ALONG ORTHOGONAL capsules, so as to give outputs that are effec- above the four corner directions (ie towards AXES, SHOWING RESISTANCES OF EACH regular tetrahedral axes). tively coincident and satisfy B- format encoding PART OF THE POTENTIOMETER TRACKS. The result is to give B- format out- The second format is B- format, consisting of accurately'. puts that are characterised by accurate and 11-yIR I1+VIA the four signals X, W, Y, Z, where X is a - precisely coincident polar diagrams up to forward facing figure of eight signal with around 7.5 kHz (as compared to less than 1.5 frontal gain A/2, W is an omnidirectional signal kHz for the best existing microphone arrays). of gain 1, Y is a sideways -facing figure -of-eight The behaviour above 7.5 kHz is arranged to be signal with leftward gain A/2, and Z is an upward smooth, although deviating from figure -of-eight signal with upward gain V/2. subjectively the ideal. In this way, the directional properties The circuit to convert A- format to B- format, of a sound field may be captured with the known as an 'AB module' is shown in fig. 1, minimum possible departure from the objective and performs the following matrixing: ideal. The microphone system should not be X =} (-Lb +Lf +Rf-Rb) W- } (Lb +Lf +Rf +Rb) regarded as four microphones on a tetrahedron, Y =} (Lb +Lf- Rf -Rb) but as a complete sound field transducing Z= (-Lb +Lf-Rf + Rb) system. The tetrahedral configuration is purely It is important to note that for horizontal only a matter of design convenience'. and has X-POI signals, the signal Z is zero, and so may be nothing to do with the desired form of B- format omitted, giving a three channel B- format signal sound field encoding. in the horizontal case. A second method of producing B- format sig- 25

www.americanradiohistory.com AMBISONICS -PART TWO A FIG. 5 TYPICAL MASKING OF PAIRWISE PAN POT (A) AND THE PROCESSING AT THE MIXER OUTPUT (B) its travel, and a matrix circuit positioned after the four output channels of the mixer. The ORIGINAL matrix circuit is exactly the same as an AB MASNy i LB module (fig. 1), except that the gain of the W / output channel is reduced to 0.707 (by reducing / LF 1 the resistor marked* in fig. to one equal to MODIFIED

0.707 of the value of the other resistors), and the FROM AB W B- FORMAT

MIXER MODULE OUTPUT Z output is not used. This gives a B format RF output. The masking of the joystick controls (SEE TEXT) is necessary to prevent undue exaggeration of / directionality of the corners. The mask for a RB joystick control normally travelling in a square aperture would as be illustrated in fig. 5. The NEW MASK side positions remain unaffected by the mask, but the corner positions are masked so that (A) (B) the corner -most joystick positions in the mask give equal outputs on the X, W, and Y outputs. Because most joystick pairwise pan pots are not well designed as regards constancy of sound level with direction, no guaranteee can be given FIG. 6 THREE- CHANNEL, FOUR LOUDSPEAKER DECODER FOR HORIZONTAL STUDIO that the ambisonic will MONITORING.THE SHELF FILTERS HAVE MATCHED PHASE RESPONSES AND GAINS modification be good ASSUME in this respect either. AT LOW AND HIGH FREQUENCIES AS IN TABLE ONE. RESISTOR VALUES GIVEN AN 11Kf1 INPUT IMPEDANCE FOR THE AB MODULE. The pan pots described give full `interior' effects as well as a 360° azimuth coverage with accurate encoding according to B- format speci- 61K fications. A similar design of about twice the complexity prior to the mixing stage, using an 16BK SHELF FILTER II additional slider pot for elevation gives full - lOK sphere periphonic encoding. Other devices of a similar nature allow the full rotation of a 2.2K whole encoded sound field (`waltz' control), a facility not possible with deiscrete approach. When sounds are `circled' with a B- format pan pot, the motion is smooth rather than the jerky jumping from speaker to speaker given by W SHELF FILTER I 10K existing pan pots. A design is also available for AB MODUL[ a `width' control that alters the width of the (SEE FIG 1i front of a sound field relative to the back b1K without destroying the correct encoding H1 specification. > 22K Having obtained a horizontal or periphonic

B- format signal, either it can be converted to SHELF FILTER II A- format (by the AB- module of fig. 1) to go 1OF 16BK through existing quadraphonic equipment, or ot* LOUDSPEAKER it can be recorded in B- format. con- RB There are LAYOUT CONTROL siderable advantages gained by staying in B- format in the tape recording stage. If one 0-FORMAT records in A- format then the effects of noise o- FORMAT INPUT OUTPUT reduction systems are quite audible when the signal is played back. Existing stereo covers only a 60° stage, and the small `pumping' effects inevitable even with a well adjusted noise reduction system do not cause noticeable movements in the stereo image. Similarly, straight from B- format. It is understood that while conventional discrete material covers 360° Table 1 Gains of shelf filters in three channel the BBC has evolved an encoding technique its very poor image quality means that pumping decoder of fig. 6. similar to B- format. The use of an optimal effects are not noticed. However, once the Shelf filter 1 Shelf filter 2 encoder ensures that the consumer-encoded image sharpness is improved by ambisonic low frequencies 0 dB 0 dB format (C- format) accurately follows the correct high frequencies +1'76dB -1.25 dB encoding, the varying image shifts (which specification. At the time of writing, no existing subjectively seem to be around 15 °) start system is considered by broadcasting organis- becoming comparatively objectionable. It is encoding equipment (with the exception of the ations and independent record companies to found that recording in B- format renders the SQ system *), provided that the Z signal of the fulfil the necessary compatibility requirements signal much less susceptible to all forms of B- format is omitted. While the results should adequately along with good four speaker image degradation whether due to channel generally be better than with existing mastertape results, and it is expected that industry discus- imbalances, phase errors, or noise reduction encoding methods, they will not be as good as sions will be held regarding the choice of a pumping. In fact, it seems likely that B- format they might be, except for the UD-4 system generally acceptable system. However, ambi- recording should reduce signal degradation which will give correct TMX encoding. sonic studio technology is compatible with all significantly even for conventional `discrete' For each of the following systems: CD4, systems capable of good localisation for all pan pot recordings. UD4, RM and the BBC matrix systems, there directions from four speakers. Ambisonic B- format signals may be con- is an optimal encoder design available working It is, of course, necessary to monitor the verted to A- format by an AB module, and may "However, an SQ encoder results of an encoded A -, B- or C- format be used, if may be used if it is set to necessary, for feeding existing 'interior' encoding mode. The results with SQ signals, and no existing decoder design is `quadraphonic' systems via existing commercial cannot be optimal. 28 26 STUDIO SOUND, AUGUST 1975

www.americanradiohistory.com Mixers by Soundcraft

5 -8 Gt Sutton Street London ECl OBX Telephone: 01- 2513631/2/3 Telegrams: Soundcraft LDN ECl

ELECTRONICS LIMITEDF v

LATEST MIXER PREAMP FROM ICE

STEREO OR MONO VERSIONS AVAILABLE FROM YOUR STOCKISTS Icelectrics Limited

1 S Albert Road, Aldershot, Hampshire. Tel: Aldershot (0252) 28S14

27

www.americanradiohistory.com AMBISONICS -PART TWO FIG. 7 DECODER FOR BMX ENCODED SIGNALS sources than one would wish to see the individ- ual phosphor dots on a colour tv screen. The a speakers are purely a means of feeding infor- `P 90 mation into the room to create a convincing (or otherwise) illusion of sounds from all directions around the listener. 1f the shape of the speaker layout deviates from a perfect square, the image stability and directional effect from the loudspeakers would alter unless SHELF I the decoder is modified to compensate a FILTER for w+D non -square speaker layout. o Other problems in designing decoders arise C- FORMAT SUM from the fact that the ears localise BMX sounds by INPUT TIFF 0-1R different mechanisms at low frequencies (< AA AR 0- FORMAT 700 Hz) and high (>700 MUDUI[ OUTPUT Hz). This means that PHASE the optimum design for a decoder is different SHIFTERS SHELF II at low and high frequencies. Moreover, when FILTER speakers are fed with signals from a matrix with +2 no frequency variation, it is found that the tone quality of reproduction is very coloured and `thumpy' in the bass (below 350 Hz). This is because at low frequencies the intensity at the +' L listener is the sum of the pressures due to the 07R four speakers, while at high frequencies it is the LOUDSPEAKER LOUDSPEAKER sum of the energies. DISTANCE LAYOUT A design of three channel horizontal studio CONTROL CONTROL decoder, working off a B- format input is shown in fig. 6. This is intended to feed a rectangular speaker layout, and the `layout control' adjusts the decoder to compensate for the actual rec- tangular shape used. The two types of `shelf filter' used have gains as in Table 1 at low and Ambisonic technology also offers new oppor- high frequencies, and are 'phase compensated' Table 2 Gains of shelf filters in two channel decoder tunities for existing mono and stereo recording. to have identical phase response. The transition of fig. 7. The sound field information from a sound field between low and high frequency gains in the Shelf filter 1 Shelf filter 2 microphone may be recorded in B- format on step filters is gradual (using simple RC type low frequencies -3.98 dB +2.04 dB four channel tape, and be mixed down later to circuits) to avoid coloration, and is centred on high frequencies 0 dB 0 dB any coincident stereo microphone technique 350 Hz approximately. that may be required. Any image width and It is found that a correctly encoded B- format microphone polar diagrams may be selected signal fed to the three channel studio monitor in a large auditorium can be quite reasonable. off tape, along with any vertical angle of tilt. gives stable and sharp images even at the sides Domestic decoders have been designed accord- A control unit to perform these functions in an of the listener and for listeners well away from ing to a range of psychoacoustic theories3 and intuitive and easy to grasp fashion has been the centre of the listening area. The four loud- at various levels of cost and complexity for all designed, and also gives adjustable 'quadra- speakers used should be matched both in the major existing or proposed surround sound phonic' outputs for four speaker use. Due to frequency and phase response, and should be systems other than SQ. It is not possible to their very good polar diagrams in the mid -treble reasonably 'omnidirectional' in their polar design an SQ decoder to satisfy the psycho - frequency region, the sound field microphone diagrams over ±45° off their respective axes. acoustic criteria established by the the author technology also gives stereo with a particularly The layout control requires careful adjustment, in ref. 3. Decoders, including layout controls `clean' and uncoloured quality of sound. but once set need not be changed. and frequency dependence, are rather similar to We have here only been able to skim over a The three channel /four speaker studio that of figure 6 and have been designed for two few aspects of ambisonics studio technology. decoder fed by B- format gives what we believe channel C- format decoding, 21 channel decod- Other devices include an apparatus to convert is the most accurate reproduction of sounds ing (as used in UD -4) and three channel certain existing types of artificial stereo reverb from any desired direction around the listener decoding. As an example, fig. 7 shows a basic units to full surround reverb, and devices for possible with existing technology via four decoder for the BMX system, with phase - compensating for and improving non -ideal speakers. It is not perfect. In particular, it was matched filters centred on 350 Hz with gains as microphone techniques that may have been predicted (in advance of construction) by a new in Table 2. This is not the most refined version used on any existing surround sound recordings. `bispectral' model for human hearing that under development; improvements to reduce Details of these and other devices will be sound waveforms with a very high degree of 'phasiness' will be announced shortly. released at a future time. asymmetry would still tend to be `pulled' to the Other decoders have been designed adjustable Ambisonic technology can, of course, be used nearest speaker position, and this is quite for cuboid (box- shaped) with -height speaker as part of existing 'quadraphonic' systems noticeable on clapping. Experiment and theory layouts for periphonic reproduction. At the (excluding SQ) by treating the A- format hori- agree here, and theory shows that there would present time, this would be confined to experi- zontal -only signals as if they were `discrete' be no way of overcoming this fault other than mental and in- studio use, where producers signals. Similarly ambisonic decoders may be going to a five speaker decoder. Many critical might find it worthwhile to explore the artistic used with existing quadraphonic systems (again listeners would possibly regard this as 'hair- possibilities of full -sphere directional effects excluding SQ). However, it will be appreciated splitting' by comparison with many existing well before they are pushed into premature that the inherent faults of the quadraphonic four speaker systems, such as 'discrete' commercial exploitation. Three and four systems will be apparent in such cases, as the encoding. channel C- format encoding has been designed whole system, from microphones or pan pots to It is not claimed that there is any decoder for periphony compatible with existing or pro- decoders and loudspeakers has to be designed capable of giving really accurate decoding in a posed horizontal C- format encoding, and it correctly for correct results. When parts of very large room or auditorium via four speakers. would even be possible to release periphonic the system are incorrect, ambisonic technology Ambisonics is essentially designed for domestic material on disc (without announcement) to will not make the system any worse, and so a or studio listening conditions, although results avoid inventory troubles at a future time. 30 28 STUDIO SOUND, AUGUST 1975

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www.americanradiohistory.com masked by AMBISONICS -PART TWO despite differing loudspeaker layouts and seating that would be completely other positions, and by giving him convincing side lines in a pan pot recording. capable of optimal results. It must be remem- localisation and smooth 'circling' effects. In bered that it is no more desirable that the four addition to existing 'interior' or 'in the head' (rotation) and 'width' effects speakers should be heard as direct sound effects, new 'waltz' References compatibility exists between ambisonics and are available as well as the first practical control 1. Michael Gerzon 'The Design of Precisely Coinci- quadraphonics -ie ambisonic material can be over with -height periphonic effects, if required. dent Microphone Arrays for Stereo and Surround used for quadraphonic results, although the When required, ambisonic equipment can cope Sound' Preprint of the 50th Audio Engineering converse is not true just as a poor colour film with existing recordings and equipment, but of Society Convention, London, 4th March 1975. cannot be made good by good projector optics. course cannot remove the faults in existing 2. Michael Gerzon 'What's Wrong with Quadra- In conclusion, the ambisonic technology material. Besides these `creative' possibilities, phonics?' Studio Sound May 1974. developed for the NRDC, and in particular by the sound field microphone allows uniquely 3. Michael Gerzon 'Surround Sound Psychoacous- Professor Peter Fellgett, the present author, accurate recording, storage and playback of tics' Wireless World, December 1974, pp483 -6. 4. P. B. Fellgett, 'Ambisonic Reproduction of and John IMF, is with natural sound fields, with all their attendant Wright of compatible in Systems'. Nature. by Directionality Surround -Sound several existing and proposed encoding systems. advantages. The 'ambient labelling°' given vol. 252, pp 534 -8. December 13, 1974. It gives enhanced creative possibilities to the the sound field microphone in particular per- 5. Michael Gerzon 'Principles of Quadraphonic producer both by ensuring that what he hears mits remarkably good sound localisation as well Recording Part Two: The Vertical Element'. Studio will be substantially passed on to the consumer as the ability to separate by ear musical lines Sound, September 1970.

ELSTREE STUDIOS cinemas when these units went in, and this was what's necessary to produce a really high all my life.' quality sound'. encouraged a large programme of standardisa- something I'd been wanting to do One problem that had to be overcome was tion and correct alignment to be undertaken in Ioan Allen of Dolby wanted to do more than that the system had to be compatible with the those cinemas which were to be equipped with use the system to clean optical tracks up: he Dolby. wanted to produce commercial films with the academy roll -off. 'The de- emphasis takes care of the effects of encoding frequencies above Elstree first became acquainted with the sound track encoded, as the pop number on the all 1 do anything about the Dolby system through Stanley Kubrick, who demonstration film had been. He asked Tony kHz but it doesn't frequencies below and the Dolby system is used the system for A Clockwork Orange. Lumkin to help him apply the already estab- as Kubrick had only used the system to keep lished Dolby noise reduction system to optical doing something to the frequencies below well the level of sound drops below a certain generation noise down in the multiple record- film sound recording. Lumkin agreed but said -if to them, so that if ing operation of the rerecording sessions. he could see three problems, which had to be level it does something could have some low Dolby had already designed a cinema noise overcome before he could recommend it to you're not careful you level traffic rumble running in a movie Dolby reduction unit that could reduce the effects of producers: could the sound track, which had up encoded which sounds good but when you play dirt, dust and scratches on the film, giving a to then been cut off at 7.5 kHz or thereabouts, it back not decoded all those low level signals noise reduction of 10 dB. It was also capable of be resolved in the laboratories; was the opera- come up 10 dB and you've got excessive traffic decoding an optical track that had been tion repeatable on one film copy after another; the wrong balance.' The solution is, as recorded Dolby processed, but such a track had and was the track compatible with sound tracks noise now, always, at the desk. 'You can equalise it in such not yet been produced. Eventually a demon- that hadn't been processed? a way that the Dolby sound is right and so is the stration film was made at Pinewood with advice After eighteen months they had overcome the academy sound. That's the only bit to worry and help from Elstree. The first such film problems. Phil Boole of Dolby, who used to in actual demonstrated only the clean up process, but at be a sound engineer at Elstree said: `One out- about fact.' Various producers had allowed them to use the end of it, there was a pop number that had come of all this has been that the processing of they were making, but the been put on to the track in encoded form. `This sound tracks in the laboratories has improved bits from movies first producer to use the system for an entire had everything in transients and all the immeasurably since December 31, 1973.' Ray it- production was Stanley Donen for The Little rest of it -which normally on optical sound- Dolby has said that the experience with the throughout even on his track would But when motion picture system had been a good example Prince. He used Dolby sound rather mediocre. to the recorded wide open, Dolby encoded and Dolby of how long it takes to go into a field, investi- Nagras. Elstree invited Donen round dubbing room to demonstrate the system. They decoded, it sounded like a pop record. It was gate the problems and learn to talk the same him two number from The out of this world, it really was,' Lumkin recalls. language as the people using the technology showed dubs of a Little Prince, one encoded and one not encoded. He saw the potential: 'I knew that Rank were under study: 'We've worked on this now for They played the encoded number back Dolby selling these equipments to the cinemas and I several years and we're still uncovering new and decoded and academy and the non encoded knew that by a commercial exercise at last one unexpected problems all the time, not only in might get a chance to control the quality in the application of our technology but in doing 56 0-

AGONY COLUMN AN ENTIRELY NEW SPECTRUM SHIFTER SOUND EFFECT

* Audio shifts up or down by 0.1 to 1000Hz for weird music and speech effects. The and wanted bongos and congas on the session, and the fixer, being from another * 'EQUAL MIX' gives phasing and beating world and age, didn't really have too many effects. contacts in that area. So someone else booked him and the session went well. * I -10Hz range for versatile howl reduction them for off applications. At the end, the fixer came in to pay everyone, including the two ethnically robed and happy - go -lucky percussionists. `Good afternoon,' said the fixer, 'I am the SURREY ELECTRONICS fixer. Are you on VAT ?' The Forge, Lucks Green, Cranleigh, `No, man,' said a voice from behind a Surrey G U6 7BG. S.T.D. 04866 5997 conga, `but if you've got some I'd love to try it'. 30 STUDIO SOUND, AUGUST 1975

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ACOUSTIC RESEARCH LABORATORY STANDARD TRANSDUCER

John Fisher

MEASURED PERFORMANCE On axis sensitivity Terminal voltage for 74 dB SPL at 1m from centre grille Speaker No Rms voltage Stereo balance AR -LST 1457 0.82 1.5 dB 1579 0.69 Intermodulation distortion To SMPTE method with 50 Hz and 7 kHz in voltage ratio 4:1 Speaker IM at SPL 74 dB 84 dB 94 dB AR 1457 0.45% 0.5% 1.1 % Frequency response data Measured on t weeter axis 1m from centre grille at nominally flat position. Positions three to six to go open- circuit but reduces the output by

74 dB SPL at 1 kHz under anechoic conditions with provide increasing If output and decreasing hf some 30 dB; replacement of the fuse cartridge B & K equipment. Both speakers of stereo pair output; in positions five and six the frequency is a simple matter. measured. balance is nominally similar to that of an The AR -LST is covered by a highly ethical Impedance AR -3a with its controls set to the `normal five -year guarantee covering parts, labour, Measured at constant current (100 mA) under position'. Output from the mid -range units is freight and if necessary packaging, but excludes anechoic conditions. held relatively constant in all six positions to thermal damage to speaker voice-coils. The Acoustic Research, 24 Thorndike Street, impression fuse does not provide protection for very Cambridge, Mass. 02141, USA. maintain the same overall of Acoustic Research, High Street, Houghton loudness at all switch positions. short -term high -level inputs, and to quote AR: Regis, Bedfordshire. It is intended that the speaker should be `will not protect the If cone if the system is used flat against a wall. Low- frequency output plugged into the mains'. They also warn that Hugh Ford will be increased if the cabinet is placed across the speaker may be damaged by attempts to a corner, and decreased if the system is not reproduce `discotheque sound levels which can close to a wall. Despite the increase in the destroy high -fidelity speakers as well as damage THE ACOUSTIC RESEARCH Laboratory number of hf units compared with the AR -3a, your hearing'. AR go on to recommend the care be taken to excessive hf energy use of speakers designed for maximum Standard Transducer is designed for applica- must avoid output fidelity tions that require `repeatable, accurately known input to the LST during, for instance, tape rather than for such applications. spectral energy profiles, including a flat searching. The speaker will withstand very The nominal input impedance drops to response'. high power inputs of short duration without about 4 ohms at various response control 10s; for 30s) and a settings. This means that a heavy connecting The AR -LST is a high -quality, high -priced damage (180W for 64W restricts cable loudspeaker of relatively modest dimensions. fuse /thermal cutout protection system should be used to handle the high level input. currents and also infers For drive unit complement, the LST uses one the maximum duration of a high that some care is A relatively 23W continuous rating is needed in choosing a power amplifier for 300 mm acoustic -suspension If unit, four 38 mm modest use given the replacement fuse unit with the LST at high levels. This is mid -range hemispherical units and four 19 mm to speaker. A situation hemispherical hf units. The individual drive is provided; spares may be ordered through somewhat aggravated by the fact that the units are identical to those of the earlier and AR. Fuse failure does not cause the speaker sensitivity is low. 34 well known AR -3a system. Crossover frequen- cies are 575 and 5000 Hz. The multiple mf and hf units provide greater power handling AR - LST No 1579 MODULUS OF IMPEDANCE than the AR -3a, each of the combinations of mf and hf units being wired in series/parallel -....M-....-N-....- (see circuit). The LST contains an auto - -....--....-N-.... -.... transformer with taps at 1 dB steps. Each of 7Z°==:M::::-.... MN the drive units is connected through its cross- 1011 _::_-.... IN NIMMONS =MENU:.IMIM... NI filter six -position switch to MINN .:'': over and a selector N--. ...CL... the transformer taps, so that the relative output .... CC....-.iN--.. N....CCC..:Vi1CN-...- levels can be adjusted as desired. A large - NINO isáüllliliirii capacitor in series with the autotransformer =I-....-- INN-.N----- !!=1111 ..7 :::----MO01:. prevents excessive amplifier loading (and also MINNC: excessive bass unit excursions) at sub -audio 111 .00. -::..-....NONNI:C _N-....-O frequencies where the transformer's inductive -ii...i= CM3illi®li0:i reactance decreases. .-MINNtC- Switch position one provides an acoustic ..-.... CC..:..-.... BERM response that rises slightly with frequency. 10 20 50 100 200 500 1000 2K 5K 10K 20K 40K The If unit output is then nominally 2 dB lower FREQUENCY IN Hz than that of the hf units. Position two is the 32 STUDIO SOUND, AUGUST 1975

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The 8034 offers real economy and this should be Everything about the 8034 is in the Neve tradition critical in your investment decision making this of excellence. And the best is what you need to year. The price is right and your investment in save money in the long run. Neve's quality of performance and service assures that the real costs are lower over the life of your console. Neve There's plenty of value for money in these 8034 The Sound of Neve is Worldwide features: Rupert Neve & Co., Ltd., Cambridge House, Melbourn, Royston, Herts., SG8 6AU England. Tel. Royston (0763) 60776 Telex 81381 Cables N EVE Cambridge Rupert Neve Incorporated. Berkshire Industrial Park, Bethel, Conn. 06801, USA. 16 track metering and recording Tel. (203) 744 -6230 Telex 969638 Hollywood : Suite 616, 1800 N. Highland Ave., Hollywood, Ca. 90028. Tel. (213) 465 -4822 Rupert Neve of Canada Ltd., 2719 Rena Road, Malton, Ontario, Canada. 20 input channels using either the 1073 Tel. (416) 677 -6611 Telex 0696 8753 Rupert Neve GmbH 6100 Darmstadt Bismarckstrasse 114 West Germany. or 1084 amplifier Telefon (06151) 81764

33

www.americanradiohistory.com AR -LST Performance General AB Pearl The speaker is available in a variety of wood Initially the contour controls were set to the and paint finishes. The test samples were nominally flat position, which was expected to Mikrofon- finished in attractive semi -matt black, with yield the most natural results, and the loud- pale grey grille cloth and brushed aluminium speaker pair were used for a period of domestic laboratorium. control knob. A screw-terminal plug is listening. This confirmed that the units were provided for connection to the recessed socket capable of a high standard of reproduction, `..ru.s ¡%cvwr íirwïs'rìsr at the rear. With reservations about the price, with a slightly `distant' sound, and that r.r.: yrrrA.vasrsrw:rsrsait rr.rr.ns...sai.rtrrtia.r./ns.s.ss the LST also makes an attractive domestic uncomfortably loud levels could be reproduced ...... loudspeaker in that it departs from the usual with a Quad 303 power amplifier. After some rrr.s..rs.ar.t11s.rrraYS..s* r.sra.T.a..r.s. box shape and will go flat against a wall; experiment the speakers were mounted on some r..vryr.r:rr ready stands about 25 cm off the .s.s.,r10urrs...s.snt certain features of its performance, detailed rough and rrr.s.r.r.s.s.rrm. below, may also commend it for domestic use ground; the contour controls were set at the VIAr.r aria nati MIN* as a quality loudspeaker. Its weight would positions one or two for subsequent listening, ter . -..+11 n as a a noticeable lack , n.r_srrt. probably discourage use of the speaker as higher settings produced :11.r..ral AMIN! monitor speaker for location work. of high frequencies. Possibly as a result of the r. . disposition of drive units, the LSTs seemed Test Conditions less conscious of room position than the The performance of the AR -LST was Spendors. assessed subjectively using direct comparison between live and reproduced sound, live Balance broadcast material and tapes considered to be With the control at position two the general of good quality. The material included speech, sound balance was pleasant and fairly natural. applause, music of all kinds and a musical box. Direct comparisons with other speakers The speakers were also used for some months suggested a slight lack of high frequencies and for general listening -including discs, broad- a slight rise in upper middle frequencies; hiss casts and tapes. Comparisons were made with and surface noise tended to become less other high quality loudspeakers, in particular noticeable than on some speakers, possibly in the Spendor BC1. part due to smoothness of the response. Direct The performance notes include the views of comparisons on speech gave the impression of a number of listeners; some with musical or a slight lack of warmth, slightly more so than technical backgrounds, some without. Some with the Spendor BC1. The effect on music of the comments were solicited, some unsolici- was masked by the apparent slight change in ted, and listening was done by individuals perspective already mentioned, and it was rather than a formal panel. While this method difficult to say whether or not a slight bass lift suffers the disadvantage that the same material (Quad 1) was necessary. Music -particularly was not necessarily heard by all those corn- strings -was felt to lack bite; use of position menting, it had the advantage that all the one was felt to give the best results in conjunc- listeners could enjoy similar listening positions tion with slight bass lift. No frequencies were and that the reviewer could also hear more found to be obtrusive and the general effect items of material in the process. Objections was of a relaxed and untiring, slightly dead can be raised to either method, the one adopted sound. In many instances there was little to being chosen as the more practical in the choose between the sound of the Spendor and particular circumstances. Listening tests were the LST when placed in similar positions. The carried out in a fair -sized room, carpeted and differences were more subtle than I had curtained and with dom -stic furnishings; :es :s expected of a multi -unit American design; were also carried out in the garden to eliminate surprisingly little trouble from interference the effects of walls and room characteristics. patterns was noticed on programme, and then The speech tests were carried out using only on certain material at less than 8ft distance recordings made with various capacitor from the speakers. Mid and high frequencies DC63. microphor.es under nearly anechoic conditions, were well distributed in the horizontal plane. 4e volt, variable patte:n to enable a good comparison to be made with Also available as the live voice. Similar comparisons were Coloration -2ardioid only DC96. carried out with a small musical box. Other than subtleties of balance, there were

For further information on the complete range of Pearl microphones, contact: AR -LST No 01457 RESPONSE AT No. 2 SETTING (NOMINALLY FLAT WITH SPEAKER Allotrope Limited MOUNTED AGAINST WALL, MEASURED FREE AIR) 90 Wardour Street, London W1V 3LP, Telephone: 01- 4371892. Telex: 21624. 30 ll: l..: =11--..C:::::.... MEIER=....= - 11...o. U.K. Representatives for: -i:...ii.=MUMM. ..ro. :: :ï.. AB Pearl Mikrofonlaboratorium - : ::::. 20 r IIM.. li-11.uu -M.... 117 IMI-M118 ...11==I= .I1 & iV..i: Sweden, Microphones accessories. :::: ' IM:::: I di -Z.... :':I IC HES Electronics - Brussels, TSV IQ :: ::'::... ''C ., C: series telephone balancing units, 10 :::0...... -M:.. =-::C:::::C and studio equipment. IMM-=.. ::..M1....©,===.rii.. --z..... Inovonics Incorporated - Camplbell California U.S.A., Audio electronics. MEE = 1 1000 2 ====:::=5 10K 20K 20 50 0 200 500 UI:- Roland Zeissler Werk Für Elektro FREQUENCY IN Hz Mechanik- Cologne, Racks and instrument housings.

34 STUDIO SOUND, AUGUST 1975

www.americanradiohistory.com few vices apparent in the way of coloration. balanced on speakers such as the LST could The bass was extremely `tight' in sound, with sound over -close and ill- positioned when little trace of booming even with bass lift reproduced through speakers producing a and /or the speaker placed across a corner sharp image. (however there was very slight coloration of white noise). The mid -range seemed particu- Sensitivity and power handling larly clear of obvious colorations on pro- Apparent sensitivity was on the low side, gramme and white noise tests. There seemed given the low impedance of the speaker. This little to complain of in terms of high- frequency need not be a serious disadvantage provided coloration, though the apparent lack of top an amplifier capable of delivering high power would tend to mask such coloration to some levels into a low impedance is available; there extent. With the contour control set at one, are however a number of European commercial there was just a trace of coloration on sibilants. amplifiers designed for 8 ohm working which cred It was nevertheless generally felt that the might prove unsatisfactory on grounds of sound, particularly with solo instruments, solo distortion and power delivered. voices, speech, etc, was subtly less transparent Power handling is adequate to generate than with the Spendor BC1; it was never harsh, painfully loud continuous sound in a large never `cardboardy' or `tinny' (how one has to listening room, and enables high levels of rely on these emotive and very subjective uncompressed speech and music to be pro- How else would youle. describe a descriptions!), but somehow slightly thicker - duced in larger surroundings with appropriate preamplifier with: translucent rather than perfectly transparent. amplifiers. * A Peak Unlimiter that restores This difference was very much less obvious on Similarity dynamics lost in recording to large instrumental and choral works. closely approximate the The sound produced by the two review original. * A Downward Expander that reads speakers, both Image on programme material and "gain riding" and expands Perhaps one of the most obvious character- white noise, was virtually identical with the dynamics down to precisely the istics of the AR -LST is the diffuse image differences completely masked by variations intended level. produced. This is presumably due to the wide due to positioning. Careful interchanging and * An AutoCorrelator that makes record /tape hiss and FM broadcast dispersion of mid and high frequencies, and to comparisons failed to reveal any important difference in character. Without a much larger noise virtually vanish without the fact that these originate from several sources affecting musical content. spaced over a considerable width, rather than sample for comparison, it is hard to give any guide to * Plus an Active Equalizer that gives from virtual point sources arranged one above as how well random pairs would match you flat energy distribution over the other. This is particularly apparent on in sound, but the results on the review samples the full audio spectrum, Joystick coincident pair recordings in stereo. Localisa- are encouraging. Balance and Step Tone Controls tion of the sounds is difficult and stability of that allow precise music tailoring Speech to the image is poor; a small shift in listening your listening environment and Speech tests involving a comparison between SQ* and Phase Linear differential position to one side produces a relatively larger live voice and a recording of that voice made logic for Quad Sound. shift in image than with, eg, the BC1. It would under almost anechoic conditions gave very be more difficult than with many speakers to acceptable results; it was occasionally, but pan spot microphones into the proper position rarely, possible to be deceived as to which was on a coincident image because of the diffuse which. The fact that it is at all possible is a effect produced by a pair of these LSTs. good sign. Contour control position two was From a consumer point of view, it could be generally felt to give the best balance. On argued that the diffuse image and slightly indoor comparisons a very slight lack of distant sound might be an advantage, in that warmth by comparison with the live voice was they blur the worst effects of too -closely noticed; this may in part be due to the differing positioned multi -microphone classical record- radiation patterns of the human body and the ings and give some spread to mono images. LST at lower speech -band frequencies. Broad- On the other hand this seems something of a cast speech was felt to be entirely natural with cart -before-the -horse approach; I can see little the switch in positions one or two in mono, disadvantage in producing a loudspeaker that The 4000 is an advanced stereo feeding one speaker only. Speech in stereo preamp that actually puts back in gives sharp images, and some dangers in the drama was well reproduced, but there was a what recording studios take out ... use, particularly for professional purposes, of lack of focus to the sound by comparison with lets your music (at last) reach life -like a monitor speaker which produces diffuse or the more analytical BC1s. Speech in double levels without distortion ... lets you shifting images. There would appear to be a mono, ie, fed to both speakers of a stereo pair, (for the first time) hear your music danger that a multi-microphone recording 36 - from a silent background. It is, in a word, incredible. Ask your dealer for an audition. Warranty: 3 years, parts and labour. AR -LST No 1579 No 2 SETTING (NOMINAL FLAT POSITION

30 mazzaii = At .i_ eArae _ 1 __=...==.o.t . =...J=.o II 20 . . .../ 1.. .11r...V.l:- ... 11Ñ...I.1_-,7 crrmPei'r dB 1=.-- .11==..111.'"...-... -111==...-__.. -M=....M=....1 10 I .-==_.___=/11.=1= -=... _=.11=1 ----..------==..-_. -a__ 4000 11111=111=.--.. ==.. =_=..1111101... = MII THE POWERFUL DIFFERENCE CO:::=:Q::....=... PHASE LINEAR FAMILY 010 20 50 100 200 500 1000 2K 51( 10K 20K luK Main Agents FREQUENCY IN R: Exposure Electronics Richardson Road Hove, Sussex BN3 5RB 35

www.americanradiohistory.com n AR-LST amplifier clipping point (some 25W into 4 IF YOU NEED ohms). The sound was generally convincing. Chamber orchestra lacked focus and immediacy. JACKFIELDS .. . As with the string quartet and solo strings, Musical box reproduction was clean but lacked attack or WHY NOT TALK Similar comparisons to the speech tests were edge on the strings on the two setting. Position made using a dead recording of a small musical one was preferred; woodwind, in particular through a single speaker were also felt to be more TO THE box. Reproduction clarinet and oboe, was good -clicks, stray noises and all -but it natural at position one; while at this setting was rarely possible to be confused, even with the sound was reasonably natural, it was felt SPECIALISTS ? slight adjustment of the Quad's tone controls by all but two listeners (who did not distinguish) to restore the top end and compensate for a that the focus and clarity of the sound were Our new Bantam range gives a space slight extra warmth in the reproduced sound better on the Spendor BCl; equally it was saving of up to 50 per cent. compared with the original; it was interesting generally felt that the sound was more distant to note that although the recordings were made and diffuse on the LST. One person com- under almost identical conditions, there was mented that the sound was `rather lifeless'. this discrepancy over the question of warmth Horn, flute and trumpet reproduced well, the of the reproduced sound. It should be said trumpet requiring the one setting to be that the difference was very slight. No obvious convincing. vices in the speakers' upper range were shown Choral music up by the test. Large -scale choral music was handled clearly, ,.cï8z ä'äEs;SEää_'Su`cSä°ä"sSa. Solo voice effortlessly and naturally, with the one position Solo singing voices, male and female, repro- marginally preferred to the nominally flat duced well with the contour control set at one position; the difference was subtle and required or two with no more than +1 on the Quad a direct comparison to illustrate. The effect control unit. On much material the flat was similar on small choirs, particularly where position of the Quad's control was preferable recorded using a coincident technique; the from a listener's point of view. As with the apparent slight lack of top and imprecise image PANELS AND ASSEMBLIES strings (below) there was a slight lack of bite contribute to set the sound farther back than evident to voices, male and female, but this with more directional speakers, and the sound, No supplier offers a wider range of panels, was by no means always noticeable and not particularly in relation to its reproduced inserts and accessories for just about any everyone mentioned the fact. Consonants acoustic, seemed subtly less clear than with the configuration. And you can get them in rarely sounded unnatural, and when they did Spendors. By comparison with a number of any stage of assembly . . . individual it was usually possible to detect the same other speakers designed or used for monitoring components, sub -assemblies, or com- feeling of questioning when one listened purposes,.the sound of the LST is much to be plete pre - wired and connectorised through other speakers. The speakers coped preferred, however. assemblies ready to install. well with loud female and boys' voices where Large orchestra the transmission medium permitted. Handled well by the speakers. Little prefer- Solo strings and string quartet ence between the LST and Spendor BCI, These were felt to lack bite and focus at except perhaps on sharpness of the image setting two; setting one was considered an when listening at some 3.5 to 4.5m, where the improvement, but the sound and focus of the LST was inferior. As mentioned earlier, for image were preferred on the Spendor BCl, in domestic purposes this might be no disadvan- stereo. The sound of violins was however tage in the reproduction of a number of always sweet, and the tone of double -bass, companies' gramophone records; however it cello and viola firm. may be doubted whether it is generally the speakers are Organ desirable, particularly where The speakers gave a full and satisfying to be used for balancing and general quality reproduction of organ music, handling bright monitoring purposes. The instability of the baroque pipes and heavy Romantic timbres stereo image with small changes of listening with equal ease. Pedal stops were reproduced position would also be a disadvantage. well, except at extreme bass where listening Large works room size and system cut -off combine to Convincing reproduction of large - scale restrict the output of fundamental; no over- choral, orchestral and operatic works at high JACKS AND PLUGS loading problem was experienced up to 38 J

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www.americanradiohistory.com the slight AR-LST one. Percussive bass sounds remained clean the piano appeared to accentuate and free from boom or obvious distress in the tonal differences between the speakers, the listening levels. Clean, tight and effortless transducers. LST producing a slightly brighter sound on sound, not matching that of electrostatics or a Plucked instruments settings one and two, yet lacking the attack small number of moving -coil loudspeakers but Apart from a slight clouding of the sound, that went with the apparently fuller tone of capable of a higher sound level than most harpsichord and guitar were well reproduced; the BCZ; I must emphasise that the difference without distress, and of more natural reproduc- it is difficult to find harpsichord material, in was extremely subtle, and neither speaker tion than many. Contour positions one or two particular, where faults in the transmission produced a wholly convincing sound, though preferred. medium, whether live broadcast, tape or disc, part of the blame for this may lie with inter- do not lead to uncertainties. More reliance mediate transducers and transmission media. Percussion in mono. The reproduction of bass drum and other was placed on the musical box test. Setting two preferred, particularly percussive sounds was particularly good, as Piano were effects in radio drama in a few instances. Good piano recordings produced a very Pop music Despite criticisms elsewhere of a lack of high acceptable sound. Perversely I found it virtually I tend to agree with AR on the subject of frequencies, instruments such as triangle, impossible to express a preference as between pop monitoring loudspeakers, this being an brushes, cymbal etc were most realistically the sound produced by the LST and the BCI, imperfect world in which the loudest loud - reproduced, particularly with the contour at either singly or in pairs, despite the fact that 40

AR -LST CROSSOVER NETWORK /SWITCHING CIRCUIT +T OA1 + OR2 POSITIONOI /TWEETER .'TWEETER \AR PART # AR PART # 02 A HA -1600 HR -1600 0 INPUT +0 - o3 TERMINALS 04 0R3 + T ARl o5 TWEETER /ITWEETER 0.1 AR PART # AR PART # STA HA -1600 HR -4600

« I Cl 6yF 01 ORS +OA6 02 MIO-RANGE MID-RANGE 03 1 AA PART # AR PART # AUTO TRANSFORMER MR-1500 MR-4500 i #6 -1dB STEPS T0 -6dB 04 240 TURNS 1dB 05 01.35mH _ O OR ORB MID MIS-RANGE 6 STO #1 -RANGE 0 2 AR PART AR PARI 3 50 TURNS # # MR -1500 MR -4500 -4 0.O44mH _o P 0006` >) -5 01 O 02 COMBINATION R1 Vv0.511 C2I11--.OpF 03 2500pF poo 5V 4 #13 + ORB 316 TURNS e-05 CC3o WOOFER 2-60mH C6 I C4 O AR PART # FUSEIRON MALLOR 6 S1C 12W 3700 C7 I C5 FPO 32361 cr\.D

Teknik 27s Graphic Equaliser

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38 STUDIO SOUND, AUGUST 1975

www.americanradiohistory.com Take a Quad 50E Amplifier (a good start for any installation)

plug it into your monitor system and it sizes include : Excellent power and frequency bridges 60052 lines to drive your speakers. response ( -1dB). Take that same amplifier and, without Low distortion (0.1% at 1kHz at all power changing it in any way, plug it into another levels). installation to deliver 50 watts into 100 volt Low background (better than 83 dB referred line * from a 0.5 volt unbalanced source. This to full output). versatility and its attendant easing of stocking Pre -set level control adjustable from front and maintenance problems is one reason why panel. large organisations use the Quad 50E. Unconditionally stable with any load. Proof against misuse including open or short * or indeed any other impedance from 5 to 250 ohms. circuited output. Small size (44" x64" x 124 ") - (120mm x 159mm x Other advantages appropriate to users of all 324mm). QUAD Products of The Acoustical Manufacturing Co. Ltd. for the closest approach to the original sound QUAD is a Registered Trade Mark Send for details to Dept SS, Acoustical Manufacturing Co Ltd, Huntingdon PE18 7DB Tel : (0480) 52561

www.americanradiohistory.com This differ- AR-LST at all frequencies may be felt to be one. My while after writing my comments). greatest personal reservation would probably ence in response as measured could be a be over the limp sound image. reflection of how far apart the serial numbers speakers do not necessarily produce the most The facility of switching the hf response is a of the two speakers were. However, one realistic or pleasing sounds at normal listening commercially useful one, since it allows the should bear in mind that with a speaker such levels with a good microphone source of signal. same speaker to be acceptable to the US and as this, using a multiplicity of drive units, a Nevertheless, with these reservations, the LST European markets and tailored, to some extent, very small change in angle or distance is likely can produce a very good account of pop music to local conditions. I would however have to produce quite large changes in response as to the loudest levels which I can tolerate for preferred separate bass and hf adjustments so measured, because of interference patterns as any length of time. I find it impossible to that raising the hf output did not necessitate well as the normal angular response variations assess the LST further in this context, except reducing the bass, and vice versa; failing that I of units. This perhaps underlines the dangers to say that it will handle quite prodigious would prefer to modify the existing switching of placing too much emphasis on the measured amounts of bass guitar. AR would doubtless arrangement to affect the hf alone. Visually I frequency response of a loudspeaker in advise on use of the LST for pop monitoring. would have preferred the control knob recessed, comparing reviews, and the difficulties of as the projecting knob spoils an otherwise correlating measured response with subjective Conclusions simple and pleasing appearance; in view of the assessment. Regardless of any preconceived notions - weight of the units I am very pleased that the about the use of multiple mf and hf units, control is not tucked away behind -though in about mounting them in a vertical line or order to discourage knob twiddling, perhaps AGONY aumN spreading them to diffuse the sound and it should be! produce a response that is more nearly omni- While I have expressed some reservations Throughout the morning rehearsal, Sir directional over a hemisphere than most about the LST, it would be too easy to read Thomas Beecham knew there was something current loudspeaker designs -it must I think too much into such criticisms as there are. wrong with the orchestra although the fault be admitted that the LST produces a very clean One manufacturer has complained, somewhat was not obvious. It took many bars before he and mostly natural quality of sound, combining bitterly and not without reason, about review- located the cause in the string section; the lady this with large signal -handling capabilities. ers `nit -picking'; perhaps it is a back-handed cellist was clearly experiencing an off day. No The better monitor loudspeakers, and listening complement when there are only nits to pick. matter how she tried, she could not control the loudspeakers, are beginning to sound more The LST clearly has strong competitors at strident noises coming from her instrument to and more like each other and like the real under half the price, but given the high cost the requirements of music or conductor. thing; subtle differences, however, remain, and of the rest of a modern studio, this is hardly Having obtained no response to appeals for it is these as much as power handling or relevant. It is most certainly a speaker to live diminuendo, Sir Thomas felt the matter appearance that must still make a final choice and work with. required a more direct approach. Without a personal one to some extent. I feel that the fuss, he dismounted from the conductor's LST just lacks the sheer transparency of sound Footnote rostrum, walked across to the string section that a small number of other loudspeakers by My comment that the two AR -LST units and whispered in the offending cellist's ear: a smaller number of manufacturers produce, supplied for review sounded virtually identical 'Madam, between your legs you have the most yet in its own way it compensates by offering is not at first sight borne out by Hugh Ford's beautiful instrument in the world. The object other subtle advantages; the wide dispersion response curves (which I did not see until some is to play it, not scratch it.'

AMBISONICS -PART ONE important feature of Ambisonics, it also converged on surprisingly concordant conclu- provides facilities for all the usual artificial sions about how surround reproduction should `effects', and some not available (or which be implemented, and there is now less doubt sonic two channel encoding also uses a cannot even be defined) in some other that the present confusion will be resolved great circle but takes account of the free- systems (see Part Two). along these lines than about exactly when it dom to tilt and otherwise modify it slightly may happen. to improve stereo and mono compatibility, Preserving options in the recording So long as uncertainty remains, it is prudent and to implement other refinements; studio for any studio to record in a form that is likely details will be published in due course. Much of the present uncertainty concerning to remain useable no matter which viable This work is very consonant with conclu- methods and standards for surround reproduc- standards are eventually adopted by the sions reached by the BBC.' tion may be ascribed to systems having been industry. Part Two consequently lays stress 3. Compatibility between surround and promulgated at a stage which now appears to on preserving options in this way. stereo playback has often been discussed have been premature in relation to the formula- without explicit realisation that original tion of adequate aims, and to the development reverberation) may come theoretical tools for implementing sound (including of adequate References will necessarily be aims. The consequence is not only lack from any direction, these 1. Gerzon, M. A. 'Surround -sound psycho- acous- encoded in some manner, and therefore of agreed standards between systems, but also tics', Wireless World, December 1974, p 483. must be located (more or less well) in some a tendency to patch up deficiencies so that 2. 'Regular Matrixed Disk Records'. Japan Phono- direction in stereo playback. Stereo there is variation of encoding standards even graph Record Association, Engineering Committee compatibility therefore involves making within what is nominally one system. So- called Standard, dated Tokyo, March 25, 1972. these directions as acceptable as possible, `logic', ie signal- controlled gain, may be seen 3. Gerzon, M. A. 'A Geometric model of 2- channel while recognising that for example origin- as a response to such deficiencies, and it is not 4- speaker matrix stereo systems' (in press). for Quadraphonic disc records'. rear positions cannot be correct in difficult to show that this stratagem is at most 4. 'Standards ally United States RIAA, Bulletin No E7, 12 September stereo playback; ie it is essentially a of only limited value. 1973. mapping operation. Once this is realised, Technological reality is however now coming 5. Scheiber, P. AES Journal Vol 19, p 835 (1971). the basic choice is seen to be largely to the fore, and it is not surprising that systems 6. Fellgett, P. B. 'Directional Information in Repro- prescribed by the need to avoid contradic- proposed with the benefit of later knowledge duced Sound' Wireless World Vol 78, p413 (1972). tions6 and this choice is followed in seem to have been preferred by independent 7. Ratliff, P. A. 'Properties of hearing related to Ambisonics. It appears not satisfactory critics, notably the Nippon Columbia BMX Quadraphonic Reproduction' BBC Research Depart- to map the comparatively small stereo system among current two -channel commercial ment Report 1974/38. T.W. J. (based on work by) 'Subjective the devil 7,8,9; it will be thought Crompton, front -sector on to itself, letting proposals perhaps not performance of various quadraphonic matrix take the hindmost and sometimes encode too disingenuous to mention that the NRDC systems. BBC Research Department Report 1974/29. it as front -sector. Ambisonic system (with which BMX is essen- 8. Shorter, G. 'Matrix Decoding'. Hi -Fi News & 4. Effects. Although the unique ability tially compatible) has come still later. Research Record Review Vol 20, No 3, March 1975. correctly to treat natural sound is an by various groups around the world has in fact 9. Holmes, P. 'Elektor Vol 1' Dec 1974 p 33. 40 STUDIO SOUND, AUGUST 1975

www.americanradiohistory.com B tween us, DI Hi -Fi sound esn't cost e earth.

These new Philips N6310 stereo headphones must be the bargain of the century - because they give just as good performance as other headphones of the same type (meeting DIN Hi -Fi 45 1500), have several extra advantages, look better and actually cost less. They have an impedance - 2 x 600 ohms - so you can use them With a 360° DIN plug, suggested with studio equipment. And you can selling price is only £12.44 including choose them reauy- fitted with the type VAT; with other plugs, slightly more. of plug you need - 360° DIN, or 6.3 mm See your Philips Dealer and post this coupon for full Jack, or Loudspeaker DIN plugs. details to:- Philips Electrical Limited, Dept SP, Century House, Built on the `open air' principle to Shaftesbury Avenue, London WC2H 8AS. give superior bass response, they give Please send me the full facts on iti6310 Headphones. smooth coverage from 20 -20, 000 Hz. Name Weight is only 160 gm, sensitivity Address 92 dB at 1 mW, maximum power input 2 x 20 mW, and nominal power output 2 x 1 mW.

PHtU/S PHILIPS Simply years ahead.

41

www.americanradiohistory.com Studio requirements for headphones ADASTRA Frequency response: 16 Hz to 20 kHz. Adastra Electronics Ltd, Unit N22, Spl: 112 dB at 1 mW (0 dBm input level). are very different from Cricklewood Trading Estate, Claremont Construction: close. those of the domestic listening Road, London NW2 1TU. Max spl: 125 dB at 20 mW at less than 1% thd. environment. Usually, Phone: 01 -452 628819. Weight: 330g. electrical and mechanical Price: £22. construction is more important H5 Impedance: 841.. than sound quality. Most Construction: close. AUDIO- TECHNICA applications are for foldback where Max power input: 0.5W. Audio -Technica Corporation, 2206 electrically lightweight cans Features: mono. Naruse, Machida, Tokyo 194, Japan. Weight: 360g. are prone to damage when the Phone: 0427 22 7641 Price: £5. UK agents: Shriro (UK) Ltd, Shriro inevitable fader is left up House, The Ridgeway, Iver, Bucks while listening to the last take G5555 SLO 9JL. in the control room. This Impedance: Bit. Phone: 0753 -65222 7. Frequency response: 20 Hz to 20 kHz. assumes escape from mechanical Spl: 110 dB at 1 mW. AT703 damage. However, Construction: close. Impedance: low. requirement does exist for Max power input: 0.5W. Frequency response: 20 Hz to 20 kHz. headphones exhibiting Features: coiled lead. Construction: close. Weight: 390g. input: 200 mW. sound quality as a primary feature, Max power Price: £15.75. Weight: 250g. such as in ob and mobile monitoring. This survey includes G8000 AT706 electret models serving both Impedance: 8!1. Impedance: low at input to inverter. Frequency response: 20 Hz to 22 kHz. categories. The demands of the Frequency response: 10 Hz to 25 kHz. Spl: 130 dB. Max power input: 10W. recording studio explain Construction: close. Features: separate inverter transforme-. the absence of some headphone Max power input: 0.5W. Weight: 220g (headphone only). models in the medium Features: coiled lead. cost bracket which optimise Weight: 350g. AT707 electret Price: £10.85. Impedance: low. neither feature. Frequency response: 20 Hz to 25 kHz. G8030 Max power input: 0.8W. Impedance: electrostatic. Features: built-in inverter transformers. Frequency response: 20 Hz to 20 kHz. Weight: 310g. Spl: 95 dB. Survey: Max power input: 10W. Features: self energising power unit. BEYER Weight: 420g (headset only). Eugen Beyer, Elektrotechnische Fabrik, Price: £46.80 complete. D71 Heilbron, Thereseinstrasse 8, West headphones Germany. Phone: (07131) 82348. AKG UK agents: Beyer Dynamic (GB) Ltd, Akustische und Kino -Gerate GmbH, 1 Clair Road, Haywards Heath, Sussex Brunhildengasse 1, A -1150 Wien, PH16 3DP. Austria. Phone: 0444 51003. Phone: (0 22 2) 92 16 47. UK agents: AKG Equipment Ltd, DT100 Eardley House, 182'4 Campden Hill Impedance: 4000 (standard: others available). Road, Kensington, London W8 7AS. Frequency response: 30 Hz to 20 kHz. 01- 229369516. Phone: Spl : 110 dB at 1 rW. Construction : close. K100 Max power input: 1W. Impedance: 6000. Features: available with various types of cord and Frequency response: 20 Hz to 20 kHz. termination. Spl: 112 dB at 0 dBm input level. Weight: 350g. Construction: close. AKG K140 Max spl: 125 dB at 20 mW. DT900 Features: high noise exclusion. Impedance: 6000. Weight: 360g. Frequency response: 30 Hz to 18 kHz. £9.90. Price: Spl: 114 dB at 1 mW. Construction: close. K140 Max power input: 200 mW. Impedance: 600i1. Features: various terminations available. Frequency response: 20 Hz to 20 kHz. Weight: 190g. Spl: 112 dB at 50 mW. Construction: open. DT480 Max spl: 119 dB at 250 mW at less than 1 thd. Impedance: Features: light weight. Frequency response: 20 Hz to 20 kHz. 175g. Weight: Spl: 115 dB at 1 mW. Price: £16. Construction : close. Max power input: 1W. K150 Features: various terminations available. Impedance: 6000. Weight: 495g. Frequency response: 25 Hz to 20 kHz. Spl: 112 dB at 1 mW (0 dBm input). DT302 Construction: open. Impedance: 6000. Max spl: 125 dB at 20 mW at less than 1 thd. Frequency response: 20 Hz to 20 kHz. Weight: 240g. Construction : open. Price: £14. Rated power input: 7 mW. Features: ultra light weight. K160 44 10- Impedance: 6001.1. 42 STUDIO SOUND, AUGUST 1975

www.americanradiohistory.com Soft contact (like Columbus's egg: a simple answer to a difficult problem)

AKG headphones K 140 'barráarr - the ones with the universal joints. Unlike eggs, Automatically adjusting headband. Soft contact. heads are not all alike. So we have developed the Large diaphragm. Frequency range: 20 -20 000 Hz. automatic headband. It adjusts itself to any size of Light metal alloy casing. Each earphone on head, gut keeps the contact pressure equally universal joint. Suitable for all hi -fi equipment. distributed. Pressure? Well, hardly any, that:, why we Available in 104 countries all over the word and from

say "soft contact". your hi -fi- dealer. www.americanradiohistory.com SURVEY: HEADPHONES SE40 HITACHI Impedance: 852. Hitachi Sales (UK) Ltd, New Century Frequency response: 25 Hz to 16 kHz. House, Coronation Road, Park Royal, Construction: close. London NW107QN. Weight: 66g. Price: £9.80. Phone: 01 -965 9861.

DT48 S E60 HD60 Impedance: 8.25 or 20012. Impedance: 811. Frequency response: 20 Hz to 20 kHz. Frequency response: 16 Hz to 20 kHz. Frequency response: 25 Hz to 18 kHz. Construction : close. Spl: 112 dB at 1 mW. Construction: close. Max power input: 0.5W. Construction: close. Price: £10.80. Weight: 420g. Max power input: 0.2W. Price: £14.90. Features: various terminations available. Weight: 400g. Eagle H2008

DT96 Impedance: 40052. HOWLAND -WEST Frequency response: 30 Hz to 17 kHz. Howland -West Ltd, 3,5 Eden Grove,

SpI: 110 dB at 1 mW. London N7 8EQ. Construction: close. Phone: 01 -609 0293 6. Max power input: 0.1W. Features: various cords and terminations available CIS 1100 Weight: 120g. Impedance: 15011. Frequency response: 18 Hz to 22 kHz. The company also manufacture modified headphone Max power input: 0.1W. sets with built -in induction loop receivers to enable Features: very thin. cordless operation. Other products include mic/ Weight: 130g. headset combinations. Price: £18.

Micro MX1 Impedance: electrostatic. Frequency response: 20 Hz to 25 kHz.

Spl : 115 dB at less than 1 °;; thd. GOLDRING Construction: close. DYNATRON Goldring Ltd, 10 Bayford Street, Features: Hackney, self powered converter. Dynatron Radio Ltd, Ditton Walk, London E8 3SE. Weight: 240g. Cambridge CB5 8QD. Phone: 01- 9851152. Price: £42.

S P -3 K -105 C1S300 Impedance: low. Impedance: 811. Impedance: 811. Frequency response: 16 Hz to 22 kHz. Frequency response: 18 Hz to 20 kHz. Frequency response: 20 Hz to 20 kHz. Construction: close. SpI: 96dB at 1 mW. Construction: close. Features: two -way driven with full x over. Construction: close. Max power input: 0.5W. Price: £21.99. Max power input: 0.5W. Features: control box, stereo /mono /volume. Price: £12.90. Weight: 400g. Price: £11.50. K -110 Dynatron SP3 Impedance: 20012. Frequency response: 16 Hz to 22 kHz. Howland West Hero HXI Electrostatic Spl: 91 dB at 1 mW. Max power input: 0.1W. Price: £18.

G RU N DIG Grundig (Great Britain) Ltd, Newlands Park, London SE26 5NQ.

Phone : 01 -659 2468.

215ADR Impedance: 40012. Frequency response: 20 Hz to 20 kHz.

SpI : 100 dB at 1 thd. Construction: close. KOSS Koss Corporation, 4129 N'Port Grundig 215 ADR Washington Avenue, Milwaukee, Wisconsin 53212, USA. UK agents: Tape -Music Distributors Ltd, 114 Ashley Road, St Albans, Herts AL1 5JR. Phone: St Albans 64337

EAGLE ESP9 Eagle International, Precision Centre, Impedance: electrostatic operation. Heather Park Drive, Wembley HAO 1SU. Frequency response: 10 Hz to 19 kHz ±5 dB. Phone: 01 -903 0144. Construction: close. Features: supplied with power unit. H2008 Price: £86.50. Frequency response: 20 Hz to 20 kHz ±5 dB. Construction: close. PRO -5LC Features: spun nylon diaphragm. Impedance: high. Weight: 350g. Frequency response: 10 Hz to 20 kHz. Price: £12. 46 0. 44 STUDIO SOUND, AUGUST 1975

www.americanradiohistory.com The RP18 and 20E headphones planar electromagnetic drive sockets. A full list of NAD are two of the finest currently system; it can be plugged stockists can be obtained by available. directly into normal headphone writing to us at the address below. The 20E is a stateoftheart electrostatic headphone and 11 TELEDYNE ACOUSTIC RESEARCH the R P18 is a new design with a High St, Houghton Regis, Dunstable, Bedfordshire LU5 5QJ.TeI:(0582) 603151

THE EARS OF GOLDRING. If you nave good sound to listen to. you can match its quality with these handsome Lenco K105 Headphones. They are good to look at. good to listen through, comfortable to wear and not expensive. Providing high quality stereo reproduction, the headphones have a frequency response of 18/22,000 Hz and an impedance of 4/16 ohms. Supplied complete with 220 cms of curled cord with a standard jack plug.

OGoldring

Goldring Ltd., 10 Bayford Street, Hackney. London E8 3SE.

45

www.americanradiohistory.com PIONEER Spl : 102 dB at 1 mW. SURVEY: HEADPHONES Pioneer Electronic Corporation, 4 -1, Construction: open. 1 Chome, Meguro, Meguro -Ku, Tokyo, Max power input: 0.1W. Construction: close. Japan. Weight: 135g. Features: individual volume controls. UK agents: Shriro (UK) Ltd, Shriro Price: £18.80. Price: £34.50. House, The Ridgeway, Iver, Bucks SLO 9J L. H D 110 PRO 4AA Phone: 0753 -65222/7 Impedance: 20052. Impedance: medium. Frequency response: 20 Hz to 20 kHz. Frequency response: 10 Hz to 20 kHz. S E205 Spl: 98 dB at 1 mW. Construction: close. Impedance: 8r1. Construction: close. Features: individual volume controls. Frequency response: 20 Hz to 20 kHz. Max power input: 0.1W. Price: £31.50. Spl: 115 dB at 0.3V. Weight: 285g. Construction: close. Price: £40.20. K0747 Max power input: 0.5W. Impedance: 600x1. Weight: 450g. Frequency response: 30 Hz to 20 kHz Spl: 110 dB at 1;,; thd. S E300 Construction: close. Impedance: piezo electric driver. SONY Features: mono /stereo switch. Frequency response: 20 Hz to 20 kHz. Sony (UK) Ltd, Central Distribution Price: £23.50. Spl: 100 dB at 3V input. Dept, 219 Bath Road, Slough, Berks. Construction: close. Phone: Slough 34611. K 0727 B Max voltage input: 30V. Impedance: medium. Features: static capacity 0.08 pF. ECR500 Electret Frequency response: 10 Hz to 18 kHz. Weight: 280g. Impedance: 30!1 at input of inverter. Construction: close. Frequency response: 20 Hz to 20 kHz. Price: £18.00. S E305 Spl: 91 dB at 1V, 300 Hz. Impedance: Construction : 'hear through'. KRD 711 Red Devil Frequency response: 20 Hz to 20 kHz. Max spl: 114 dB. Impedance: 600!!. Spl: 108 dB at 0.3V input. Features: impedance converter supplied. Frequency response: 10 Hz to 17 kHz. Construction: close. Weight: 350g (headset only). Spl: 110 dB at 0.5" thd. Max power input: 0.5W. Price: £57.50. Construction: close. Weight: 435g. Features: crunch proof. Weight: 340g. S E700 Price: £12.50. Impedance: piezo electric driver. Frequency response: 20 Hz to 20 kHz. STAX 1A HV Spl: 100 dB at 3V. Stax Industries Ltd, 25-5 Zoshigaya, Impedance: 600rr. Construction: close. 1 -Chome Toshima -Ku, Tokyo, Japan. Frequency response: 15 Hz to 20 kHz. Max voltage input: 30V. Phone: 03 -981 7227. : 109 Spl dB at 0.5" thd. Features: static capacity 0.1 µF. UK agents: Wilmex Ltd, Import Division Construction: open. Weight: 295g. Compton House, New Malden, Surrey Features: 'high velocity' driver. Weight: 260g. KT3 4DE. £26.50. Price: Phone : 01 -949 2545. Pioneer SE 305 SR5 and SRX /3 Impedance: electrostatic. response: 30 Hz to 25 kHz. Koss ESP9 Frequency SpI: 110 dB maximum. Construction: close. Features: power units with varying spec. available. Weight: 390g and 380g. Price: £42 and £88. Power units priced about £30.

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W675 SENN HEISER Frequency response: 20 Hz to 20 kHz. Sennheiser Electronic, 3002 Construction: open. Bissendorf /Hann, West Germany. Features: DIN 5 pin plug. 8011. Phone: (05130) Price: £24.90. UK agents: Hayden Laboratories Ltd, PHILIPS Hayden House, 17 Chesham Road, Philips Electrical Ltd, Eindhoven, Amersham, Bucks HP6 5AG. Netherlands. Phone: 02403 -5511. UK distributor: Philips Electrical Ltd, WHARFEDALE City House, 420 London Road, Croydon. H D 424 Rank Radio International, PO Box 596, Phone: 01- 689 2166. Telex: 946169. Impedance: 20001.2. Power Road, Chiswick, London W4 5PW. Frequency response: 16 Hz to 20 kHz. Phone: 01- 994 6491. N6310 Spi: 102 dB at 1 mW. Impedance: 600rr. Construction: open. ISO DYNAMIC Frequency response: 20 Hz to 20 kHz. Max power input: 0.1W. Impedance: 100! 2. Spl : 92 dB at 1 mW. Weight: 190g. Frequency response: 16 Hz to 22 kHz. Construction: Open air principle. Price: £27. Spi: 95 dB at 30 mW. Max power input: 20 mW. Construction: close. Features: Available in 3 types of plugs. HD414 Max voltage input: 23V rms. Weight: 160g. Impedance: 2000D. Features: 120 dB spl at 0.1% thd.

Price : £10.46. Frequency response: 20 Hz to 20 kHz. Weight: 450y. 46 STUDIO SOUND, AUGUST 1975

www.americanradiohistory.com An exciting newçoncept in tereophonc listening Koss engineers have developed a new phase to stereophone the centre of a live performance. listening. A concert so exz ting and so different from other Now flip the Ambience. Expa,de- switch on the right earcup stereophones, we called it Phase 2. to the E posi:icn. You'll heat a ctamatic expansior of the centre Ir effect, Koss Phase 2 Stereophones do for the music lover charnel on yo_r recorcing ttat glues you incredibly enhancad wl-at the zoom lers cid for the photographer. By binging the dent- and rich-ess. Then rotate one control separately from tie orchestra into vivic close -up or expanding the other; it's like sitt ng on :he piano benc' one inirute musical sphere surrounding you so that you and in the rricst D_ :he violin secion the nct. feel encircled by a panorama 01 sound. To go mc< tc canventioral sound, set You have the option of personalising the Ambieice E >pander on J position and each stereo recording as i' it nad reduce the Panoramic Source Contols been tailor -made b your individual on both ears :D zero. As an addec ocn- taste, being aale to do things that vemence a Momentary Comparator unti now only a recording engineer sw tch 31 the let* cup lets you cou d do at tt-,e origin s ssior. acmpare the new sound The secret is the rotatñg capabilities with The Panoramic Source Cortrol located coiventioral stereo mxfe. at the lower edge of eact- earcup. Ask your Audio Deale- to They range from zerc to 10, and ,et you hear Koss Phase 2 as you acvan:e the level you fee Stereophones. Ard write drawn doser and :loser toward for our free full -eclbur catalogue

www.americanradiohistory.com The high levels of sound now IF YOU STAND with unprotected ears near a noise level limits. Unfortunately it gives no generated by bands on stage and steam hammer, a rifle range or a sheet metal guidance over the actual limits which should be by monitor speakers in studio working machine, you will suffer a shift in the imposed. Thus it is possible that other local threshold of hearing. In other words, your ears authorities will soon take action similar to control rooms may constitute a long thus Leeds which will be criticised as over- protec- term risk to the hearing of musicians, will become accustomed to the noise and attenuate it, deafening you to quiet sounds. If tive. There are signs, already, that the GLC has audience and engineers. exposure to the loud noise is only brief, then plans to impose sound level limits on public the threshold shift will only be temporary, and music performances and, although the levels your hearing will return to normal within hours which the GLC is considering are higher than or at the very most days. However, if exposure those adopted by Leeds, it is likely that they continues, day in, day out, year after year, the would still outlaw the louder concerts and Hearing temporary threshold shift will become perma- clubs. nent and you will start going deaf. This has long The single most informed critic of Leeds has been accepted as an occupational hazard in been Sandy Brown Associates, who produced a damage some areas of industry. The phrase `deaf as a report to the Association of Ballrooms on weaver' sums up the inevitable result of a Hearing, Health and Musico. Much of the Leeds lifetime spent working in a jute mill. action was based on work carried out" B and ADRIAN HOPE We hear because sensitive hair cells in the ear conclusions drawn by R. W. Fearn, Principal sense air pressure changes and transmit impul- Lecturer at the Department of Architectural ses to the brain. Excessive sound creates Studies at Leeds Polytechnic, and the Brown excessive pressure on the cells and this causes report disagrees with both Fearn's conclusions the damage. When the damage is temporary, and the Leeds measures. But Sandy Brown has, the shift of threshold is temporary, and when for years, publicly expressed fears that exces- the damage is permanent the threshold shift is sively loud amplified music constitutes a permanent. The process of permanent damage hearing risk, and one of his associates, Alex is slow but irreversible and because the process Burd, has published his views on the problem is slow, the effects often pass unnoticed for as an AES paper'. It is this background that years. When the threshold of hearing has risen makes the report by Brown on the Leeds by about 25 dB, then there will be a slight measures so important; most of the other impairment in the understanding of everyday vociferous attacks on Leeds have been launched speech. When it has risen by 30 dB, the sufferer by parties who have absolutely no understand- will realise that something is going seriously ing of the complex acoustic and medical issues wrong with his ears and consider the use of a involved and, who often have vested financial hearing aid. A hearing aid will not repair the interests in loud music. Also Sandy Brown damage, but simply amplifies sounds to reach made clear to the Ballroom Association that if higher thresholds. Unfortunately, hearing loss he took the commission the Association would is often more than a simple shift in threshold; have to foot the bill, whatever the conclusions. the upper frequencies may be rolled off more In the event the Association, in Brown's drastically than the lower, and this will make words, `was lucky'; report found Leeds over- speech unintelligible. Try this for yourself by protective. playing a dialogue disc or tape and roll off the It is possible that some STUDIO SOUND readers top frequencies-the dialogue becomes muffled have already suffered in one way or another and no amount of gain boosting can repair the from the Leeds decision. Certainly, pop groups problem. now shun the area, and the only live music is Although it has long been known that indus- orchestral, classical, folk or anaemically ampli- trial noise constitutes a risk to hearing, it was fied, soft pop. This must inevitably have not until the 1970 Department of Health & affected local promoters and if the leeway given Social Security Report, Hearing and Noise in by the Control of Pollution Act is taken up by Industry, by W. Burns and D. W. Robinson,' other local authorities, then the same situation that a serious attempt was made to evaluate the may soon exist in other parts of the United problem statistically and quantitatively. The Kingdom. But most important to people in the report was followed in 1972 by a Department of business is the fact that there is danger. There Employment Code of Practice for Reducing the are now few informed observers now who will Exposure of Employed Persons to Noise,' and put hand on heart and argue that the Burns and these two documents are now standard refer- Robinson warnings over noise and hearing loss ences. Neither investigates the possibility that do not also apply to excessively loud music. excessively loud music can be regarded as Unfortunately, few people can agree on just synonymous with industrial noise, but over how music can be equated with industrial recent years this suggestion has been put for- noise, and thus what the real risks are. But as ward with increasing persuasion. studio engineers are more likely to be running The first positive action was taken by the those risks (whatever they are) than any other Leeds local authority, who invoked powers sector of the community, they would be well have made available to them by the Leeds Corpora- advised at least to consider the facts that tion Act of 1906, to impose a statutory limit of been established and the various interpretations 96 dB(A) on musical performances in the area. that have been placed on them. But although this action was born of the best Although many people will be familiar with motives, it has been strongly criticised on the dB scales of sound measurement, a crisp several counts. Probably the most pertinent reminder of the definitions may not come amiss criticism is that the limit adopted is in practice because they are essential to an understanding over-protective. Although, at the time of of the topic. writing, the Leeds limit still stands at 96 dB(A), Sound is conventionally measured in units of it is unlikely to remain so for much longer. pressure or intensity at the ear. The basic unit The Control of Pollution Act, 19743, how- of sound pressure is the newton /square metre the ever, gives wide powers to local authorities (N/m'), and the basic unit of intensity is throughout the United Kingdom to impose watt /square metre (W /m'). Both measurements

48 STUDIO SOUND, AUGUST 1975

www.americanradiohistory.com are most conveniently expressed on a dB scale, two hours, it can be 96 dB(A), and so on Burns and Robinson and the Code of and the following formulae are used:- upwards-until the upper absolute limit of Practice offer an answer to the problem of Intensity level in dB =10 loglo(i /io), where i 135 dB(A) is reached. evaluating the risks of non -steady noise. This is the intensity of sound in W /m2 and io is the Levels of noise which indicate a serious is based on the use of Leq or `equivalent reference intensity level (0 dB) of 10- 12W /m2. hazard to hearing continuous sound' levels. This gives a value for Sound pressure level in dB =20 log,o(p /p0), Exposure duration Maximum sound level exactly what the name implies -the sound level hours per day dB(A) where p is the sound pressure in N /m2 and Po that will produce sound energy and effects 8 90 is the reference level (0 dB) 0.00002N/m2. directly comparable to a continuous sound 4 93 of The two reference levels given above are 2 96 the same numerical value. A conventional sound generally regarded as standard and were 1 99 level meter (reading in dB (A) will indicate a deliberately chosen to bring the intensity and 102 true value for Leq only when the sound level sound pressure dB scales substantially into line. 105 being sensed is continuous and steady. If the However, because sound power energy or Fearn, in Leeds, carried out meticulous and sound is discontinuous and erratic in level, then intensity (analogous with electrical power) is extensive tests on the hearing of young pop Leq can be defined mathematically by the proportional to sound pressure (analogous with club and concert attenders, comparing them following equation: electrical voltage or current) squared, a with control subjects who did not attend. He Leq =10 logs r T [PA(t)]z dt doubling of sound power, intensity or energy is concluded that the loss of hearing which the 0 poz subjects exhibited indicated that Burns and written as a 3 dB increase and a doubling of where: lines Leq = level, normal- sound pressure is written as a 6 dB increase. Robinson's guide for industrial noise equivalent continuous sound ised to an eight hour exposure Virtually all dB values likely to be found in these were equally applicable to pop music noise. It was this that brought Leeds to impose the T =total working period in hours pages, and bandied around in the context of PA- instantaneous A- weighted sound pressure noise -induced hearing loss, are sound pressure 96 dB(A) maximum level limit. Brown argues that music, even the most monotonous pop in N /m2 level meaurements, and most sound meters are Po-reference rms sound pressure as specified music with the smallest dynamic range, cannot in fact sound pressure meters. However, such in BS 661:1969 clause 2006, viz 2 x 10-5 meters normally have weighted response curves. reasonably be equated with continuous levels of N /m2 The `C' curve or scale represents nearly flat industrial noise. This raises probably the most /-time frequency response and the `A' and `B' scales important single point to emerge from the It should be borne in mind that because involve various degrees of low frequency sup- whole mass of confusion and half -truths which Burns and Robinson were working on industrial pression. These scales are intended to compen- have been bandied around over recent years. noise, all their deductions and predictions sate for the non-linear response of the human The Burns and Robinson Report and Code of centre round an eight hour day or 40 -hour ear to different frequencies at different levels. Practice clearly indicate that sound should not week. This has become the standard currency of Most of the meters which engineers are likely be regarded as continuous unless it is reason- noise risk. Thus when equivalent levels are to encounter in studio or allied work will read ably steady and never fluctuates by more than given they are normalized to an eight hour day on the `A' scale, and although this is not 8 dB(A). But, very little if any pop music, and require further adjustment if they are to be regarded as ideal for noise risk measurement falls within this category. applied to shorter periods of time, such as pop purposes, it has been almost universally adopted concerts, or longer periods of time, such as as a reasonable working compromise. all -night mix -down sessions. As an example, an Leq level of 90 dB(A) normalised for an eight The normal threshold of hearing of the t. hour day would not be exceeded by a two hour human ear is such that a sound 0 dB(A) is only of 125 - concert or session with an Leq of 96 dB(A). just audible. Normal conversation, television Also, because we are talking in terms of Leg or radio listening levels are around 60 dB(A), a rather than peak readings, that two hour - loud factory or workshop has an average level L., session could contain sound levels of well over pop 120- of around 90 dB(A), most discotheques or 120, -6 96 dB(A) provided that they were between levels levels 100 dB(A), 6 groups produce sound of over of below 96 dB(A). For instance, one minute at a jet plane at a couple of hundred yards notches e 105 dB(A) would require 32 minutes at less up 120 dB(A), and at 135 dB(A) the around than 90 dB(A) to maintain the 96 dB(A) Leg is likely to instantaneous 115 - 110 human ear suffer level. 2 permanent damage. At 150 dB(A), the whole The Department of Employment Code of is at risk. But it is for body not uncommon 80- Practice contains a useful, nomogram for studio control room levels to be at around -, 60 calculating equivalent continuous sound levels 120 dB(A) when pop music is being monitored, 110- 100- <0 from discontinuous levels. Simply take a ruler and levels of 128 dB(A) are not unkown. and draw a straight line between the measured Working with industrial noise, Burns and sound level in dB(A) on the L scale to the time 20 Robinson concluded that only sound levels of the t scale. The point at which 105- of exposure on under 80 or 85 dB(A) can be regarded as 90 the line crosses the centre scale gives the Leg. totally safe. In the more realistic middle ground 10 Thus exposure of 90 dB(A) for eight hours gives in between this and the `instantaneously an Leg of 90 dB(A); but an exposure of 102 dangerous' 135 dB(A) level, Burns and Robin- dB(A) for two hours fifteen minutes per day 100- 60 son suggested that the human ear must be 4 gives an Leg of 96 dB(A). regarded as being at long term risk if it is It is also worth bearing in mind that noise exposed for eight hours a day to continuous 2 dose meters are now coming onto the market sound levels of over 90 dB(A). So, if this level 95 - which will give a direct reading of Leq. Thus and duration is to be encountered, then ear 60 the time may come when studio engineers will If 60 1i protection, eg ear muffs, is needed. Still work- wear Leg dose meters just as workers with ing with the notional concept of continuous radioactive materials consistently wear radia- is case in sound (which often the practical 90 - tion dose meters. industry where machines create noise all day Sandy Brown's report points out the fact at virtually constant levels) Burns and that even the most monotonous sounding pop Robinson laid down the guide line for safe music has an Leg level which is substantially exposure to higher levels. Each halving of the 65 lower than the maximum level that the music duration of the eight hour day permits an reaches. In one discotheque visited by Brown's increase of 3 dB. Thus, if exposure to contin- NOMOGRAM FOR CALCULATION OF researchers, the Leg measured with a dose uous high level noise is for four hours rather meter was 92.5 dBA. and the maximum level than eight, the noise level can be safely EQUIVALENT CONTINUOUS SOUND LEVEL increased to 93 dB(A). If exposure is for only 50 49

www.americanradiohistory.com HEARING DAMAGE ( L,+IO log,, (T/T,)+Up-ai H 27 .5 [ I-rtanh Up which the meter read during the evening was IS / 102 dBA. The Leg calculated by statistical analysis was 91.4 dBA. In another discotheque the Leg as measured by the dose meter was 96.3 dBA, the maximum level recorded was is far more risk prone than fifty per cent of the is a comparatively new occupation, and that the 104 dBA and the Leg calculated statistically population, and how hearing loss hits hardest progress of noise induced hearing loss, although was 95 dBA. Thus, in the first discotheque there at 4 kHz (so- called 4k dip). But any dip at sure, is slow. 1 was a discrepancy of 9.5 dBA between maxi- 1 kHz is important because that frequency is This can be his downfall, but the knowledge mum and Log levels, and in the second disco- in the middle of the main speech band. of it can also be his salvation. Anyone who theque there was a discrepancy of 7.7 dBA. Equivalent Predicted hearing loss dB feels he is at risk has time on his side. If he is noise At 1 kHz At 4 kHz Leeds prepared to have his hearing checked out every refuses to work with Leg (or has so level 10% 50% 10% 50% far refused), on the grounds that there can be year or so, he will have a clear picture of any dBA level level level level loss that is accumulating. Once he knows he is no knowing what the disco or concert attend - 91 6 0.6 15 2 suffering a loss, he can take steps to curtail it, ers have been doing where they have worked 95 10 1 20 5 for instance by cutting down on pop music during the day. But in this Leeds is accused of 97 11 1 22 7 being over -protective. Critics maintain that 100 12 2 27 8 monitoring or cutting back on levels from the majority of disco and concert attenders, 107 18 3 38 17 speakers (or headphones because it is, of who work in quiet surroundings during the Put in words of one syllable, if ten sound course, only too easy to produce dangerously day, should be allowed to enjoy loud music engineers expose themselves eight hours a day high levels on phones). Once an engineer at night if they wish, and should not be penal- for five years to equivalent noise levels of realises that he has a problem, he could well ised because a few attenders will have been in 107 dB(A), then one of them is likely to suffer consider the possibility of wearing a sound dose noisy surroundings during the day. a hearing loss of 18 dB at 1 kHz and a staggering meter to warn him when he is at risk of 38 dB at 4 kHz. The 107 dB(A) level is high aggravating this hazard. On the other hand, Most of the argument in this article has so but not unknown by studio standards. of course, he could simply cross his fingers and, far been academic. Because excessively loud I find this quite horrific and can only hope, like drunken drivers, heavy smokers and over- amplified music is a relatively new phenomenon for the sake of many studio engineers, that there ambitious amateur rock climbers, reckon that and hearing damage is slow to appear there are is a flaw in the chain of calculations using the 'nothing like that will ever happen to me.' 1 few people who are sufficiently deaf to cause Burns and Robinson formula and my interpre- immediate concern. And it can always be tations. But I doubt it. Likewise I hope, but argued that those who showing signs are of doubt, that there is a flaw in my interpretation deafness would have done so anyway. This is of the calculations put forward by Sandy perhaps, the problem facing biggest the indivi- Brown, also on the strength of the Burns and dual. Is he to believe the prediction of hearing Robinson formula. These suggest that if ten loss made by Burns and Robinson and echoed References and further reading sound engineers work for four hours a day for 1. Hearing & Noise in Industry. Burns, W. & by R. W. Fearn in Leeds, or is he to regard them two years at an equivalent level of only 100 Robinson, D. W. HMSO. £1.75. as unproven and not worth considering? If the dB(A), then one of those ten can expect a 2. Code of Practice for Reducing the Exposure of arguments linking noise and music are ever hearing loss of 8.7 dB at 500 Hz, of 9.3 dB at Employed Persons to Noise. HMSO 1972. 52 }p. conclusively proven, there will be by then large 3. Control of Pollution Act 1974, Chapter 40. HMSO. i kHz, of 11.4 dB at 2 kHz, and 17 dB at 4 kHz. numbers of pop fans and engineers who are £1.22. In this connection, mark well that the American already suffering from possibly substantial and 4. Hearing, Health & Music-Report to the Associa- Academy Ophthalmology irreversible hearing loss. In any case, if the of and Otolaryn- tion of Ballrooms. Sandy Brown Associates, 12 regards a hearing loss 25 attitude of the public towards the warnings gology of dB as the Conway Street, London W1P 5HP. beginning of impairment understanding 5. Leeds Department of Architecture. Reports Nos. repeatedly offered them over the risks of smok- of spoken English. AS71/5 and AS72/7: Pop Music and Hearing ing are a reliable guide, then even when there is Before anyone shouts !' Damage. Fearn, R. W. concrete proof that loud music causes hearing 'scaremonger too loudly, let him first try telling a joke softly to 6. Physics Bulletin, October 1974. Letter, p.422. loss, many people will still bury their heads in Fearn, R. W. someone who has worked half his life in a sheet the monitors and ignore it. 7. Hearing Damage from Music -UK experience. metal factory or a jute mill. Let him then Burns and Robinson produced a formula Burd, A. J. Audio Eng. Soc. September 1974. remember that monitoring music at high levels 8. World Medicine. August 11, 1970, pp.21 -25. which gives the noise -induced hearing loss H which can be expected in a given percentage P of a normal population which is daily subjected to a noise level LA2 over a period of time T. This formula is written as: (see above) where Xi is a constant depending on sound Recent events thicken the plot and raise many more questions than they answer. The Greater frequency, To is a reference duration and Up London Council has published a draft Code of Practice that places industrial limits on is a constant depending on the selected per- entertainment. Although the Code is not yet formally in force there are signs that it is already centage P. LA2 is a sound level reading that is making its presence felt, for instance when conditions are attached to licences given by the GLC not exactly the same as the noise level L which to concert promoters. can be read directly off a sound level meter, The GLC limit is the Leg recommended by the British Government and the ISO as a but Burns and Robinson give conversion guideline for industry--a daily eight hour dose of 90 dBA continuous sound, or the tables for this and parameters other in the energy equivalent in discontinuous and varying sound spread over the duration of the concert. equation. Tests I have run in the London area show that this limit effectively kills all loud As only the most mathematically active music stone dead. One pop group clocked up the full safe GLC dose for the day in around minds will feel inclined to work out their own quarter of an hour-and they weren't particularly loud at that. A disco with a predictions from this formula, I will plagiarise moderate sound system hit the full daily dose in not much over one hour, even though there was the published work of R. W. Fearn and Sandy segué sound in the club for hour and a half hours a night. Most interesting of all Brown to give the following examples of what was the reading from a virtually acoustic jazz piano trio-86% of a full daily dose in two hours type of risk can be predicted from Burns and playing time. By this token every musician who has played a lifetime in a jazz big band Robinson's work. (such as Basie, Ellington, Heath, Kenton, Rich, Goodman) should be well and truly deaf by now. The following table shows what can be But as far as I know they aren't, so is the ear more tolerant to 'nice' noise than 'nasty'? No-one expected after five years of eight hours a day seems to know or care, but I am currently looking into this possibility and would welcome exposure at various equivalent levels. Thus the any comments that any readers may have for inclusion (without attribution, if requested, of table shows how ten per cent of the population course) in a further article shortly. 50 STUDIO SOUND, AUGUST 1975

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www.americanradiohistory.com AMBER MODEL 4550 AUDIO SPECTRUM DISPLAY

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MANUFACTURER'S SPECIFICATION Frequency range: 20 Hz to 20 kHz. Quantity of bands displayed: 10 octave-width '! t6 bands. _. Centre frequencies: 31.25, 62.5, 125, 250, 500 Hz, 76. 1, 2, 4, 8, 16 kHz. .... 2 Centre frequency accuracy: ±5% internally .. adjustable. slope (asymptote): 12 dB per octave. Filter _8----i4-..._,,.._..-x__..-.-_ / Display range: 10 or 20 dB selectable. e _.?S---ar-.... Accuracy of dB steps: ±0.25 dB non -cumulative. ..._' -6 Input Sensitivity range: 0 vu may be calibrated to level between dBm indicate any absolute input -12 aus b'!-5 125 - '1O as Spp tk Iy -°--Ak -----` and +12 dBm. Normally supplied with O vu= +4 dBm bk 16k 8, calibration. Front panel attenuator range: 20 dB in 2 dB steps. Attenuator step accuracy: ±0.25 dB non -cumu- lative. Display Amplitude accuracy: +0.25 dB for a steady sinewave at filter centre frequency (internally adjustable). Quantity of audio inputs: 4, individually selectable. Input impedance: greater than 18 kS . Quantity of memories: 2, independent. Maximum storage time: virtually indefinite with continuous ac power. Display response time: display indicates within good high frequency saturation performance is So much for the display, and now to the really 1 dB of actual value; within 2ms above 1 kHz or 4 sometimes copied without `treatment' onto a novel features. Being a digitally operated display cycles or less 1 kHz and below. compact cassette format which has relatively the technique offers the possibility of operation Display decay time: to fall 20 dB takes approxi- poor high frequency saturation characteristics in real time and from a digital store. The Amber mately 2.3s. result being a terribly `mushy' cassette instrument takes advantage of both modes. In Power requirements: 120/240V ac ±10% 48 to -the from clean master tape. real time, two operating states are possible. In 62 Hz, 25 va. being copied a filters act upon the input Size: (excluding handle and feet) 133 x 210 x 279 mm. Hitherto, the way out of these problems has the first, the band Weight: 3.6 kg. been by purely subjective assessment of the signal producing spectral amplitude content on Price: UK: £880, US: $1800, Canada: $1600. programme material; the only suitable instru- the display. In the second, all the display Manufacturer: Amber Electro Design Ltd., 613- mentation has been a very expensive real time bands are run in parallel giving a single 100 Francois, Montreal, Canada. analyser costing several thousand pounds. channel ppm indication. UK agent: Scenic Sounds Equipment, 27/31 While the Amber audio spectrum display is, A rotary four position switch selects the London WI. Bryanston Street, in effect, a real time analyser, it has been specifi- display data from either of two separate Phone: 01 -935 0141 cally made for the recording industry and does memories or from the two 'live' modes without not require the extreme accuracy of previously affecting the accumulation of data by the available instruments. It does, however, have memories. These are controlled by three push perfectly adequate accuracy for the purposes for button switches for each identical memory. The which it is intended and also includes some first of these erases the contents of the chosen novel features which are not found in other real memory, such that the memory is ready to time devices. accept new data. Two modes of data entry are WHILST NORMAL PROGRAMME level To start with, the display consists of a 10 x 10 available: the first is a 'sample' mode in which meters give an indication of the overall pro- matrix of light emitting diodes, each vertical the memory accumulates data when the 'sample' gramme level, it is of course desirable to have row of which indicates level in either 1 dB or push button is depressed; the second is the some knowledge of the spectral energy distri- 2 dB steps within one of ten octave bands. 'enter' mode which is controlled by a locking bution, because all current methods of audio These are arranged to correspond to the hori- 'enter' push button. While this button is recording reach a saturation point which varies zontal axis of the display. The centre frequen- depressed, the selected memory accumulates according to the frequency of the incoming cies of the ten filters are arranged from 31.25 Hz data and stores the maximum levels in each signal. In the cases of tape recording and fm to 16 kHz, thus covering the audio spectrum of octave band. It follows that it is possible to broadcasting, pre-emphasis is used to increase normal interest. Unlike the expensive precision accumulate the spectrum from two different the available signal to noise ratio, and such pre - analysers, the filter shape does not aim to have sources (say master tape and 'treated' copy emphasis directly affects the saturation point of the normal rectangular response as is essential master) and to directly compare the spectra at the system. Similarly, in disc recording, there is for other applications. Another important the turn of a switch. Furthermore, the display the standard RIAA curve and the mechnical difference is the fact that the Amber device uses may be operated in any mode while data is consideration of the system to be taken into a peak rectifier with a fairly long time constant being accumulated. account. hold circuit as opposed to the genuine rms Many other modes of use will come to mind An even more serious situation arises in tape rectifiers which are essential for spectral density when it is realised that the unit has four separate duplicating where a high speed master tape with determination. 54 52 STUDIO SOUND, AUGUST 1975

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www.americanradiohistory.com AMBER 4550 board to which are mounted three sockets for The final matter affecting the overall level the subsidiary boards, one of which forms the accuracy of the instrument is the operation of display. The mother board may be readily the +10 dB step attenuator. This gave a inputs which are isolated from each other. removed, as all the front panel controls and creditable worst case error of 0.3 dB between Either individual inputs or the arithmetic sum rear panel functions are wired to the mother steps or 0.33 dB absolute error overall. of any combination of input signals may be fed board via plugs and sockets. However, I do to the display in accordance with the setting of have one relatively serious complaint about the Display response the four input selector push buttons. The final construction, and this relates to electrical It was found that the rectifier characteristic was front panel facility is an input attenuator which safety. As has been found with other American to true peak, which is probably the best for the covers a +10 dB range in 2 dB steps, the zero products, the mains voltage selector is in the intended application of the instrument. How- point being determined by the setting of a rear form of a truncated slide switch which has ever, this characteristic does mean that the panel calibration control. too small a clearance between its solder tags instrument is not suitable for frequency To the rear of the instrument are the four and the metal case fixed to the instrument response alignment using random noise electronically balanced inputs in the form of chassis. sources and, in this respect, both the sales three pin XLR sockets, and IEC standard leaflet and the instruction book are misleading. mains input, mains voltage selector and mains Calibration The effective rise time of the display is very fuse, all of which are clearly identified. In addi- As supplied, and with the step attenuator set to fast, such that an indication within 1 dB of the tion, there are two calibration controls for zero, the 0 vu indication of the display corres- final value is reached in 500 u.s with a 16 kHz adjusting the basic input sensitivity and for ponded to +4 dBm with the display in the sinewave input, reducing to 1 ms at 2 kHz and setting the dB per step of the display. Con- 2 dB per step mode. However, the rear panel about 8 ms at 250 Hz. The display then holds cluding, the auxiliary input for remote actua- calibration control had a range of 24.7 dB with the final value with an effective measured fall tion of the `sample' mode of either store and the this initial setting near the centre of the range. time of 1.4s to -20 dB. While the fall time auxiliary output. The latter is intended for One thing that was found to be rather confusing leads to the display being easily read, it may be using an oscilloscope to display the spectrum was that, when changing from the 1 dB to the felt that the effective rise time is too fast such of the incoming signals and provides a time - 2 dB per step mode, the minimum display that the instrument may display peaks base trigger and a `Y' input. The resulting indication remained at a constant input level. which cannot lead to audible distortion- display is in the form of a vertical `bar chart' as opposed to the 0 vu point remaining at however, the proof of the pudding is in the with the rise and fall times of the instrument. a constant input level. eating. Probably the user will wish to set the overall Construction sensitivity, but will not wish to adjust the Inputs and outputs The external and internal appearance of the individual centre frequencies and gains of the Whilst I have already mentioned the input instrument are both neat and tidy with all ten filters, all of which are adjustable by inter- sensitivity using the balanced input, it should operational facilities being clearly identified. nal preset controls. This parameter, therefore, perhaps be mentioned that the active input However, while the individual components are was investigated in some detail. In practice the circuit is such that the sensitivity is identical in not identified by component references, the centre frequencies were found to be within 3 the unbalanced mode, but that the input layout and all details (both mechanical and of nominal in the worst case, and the level impedance is lower. The impedance of the electrical) are given in the first class instruction accuracy of the filters within 0.3 dB overall balanced input was found to be 17.8 kû when manual which is provided with each instrument. error, with the exception of the 16 kHz filter the input was not actuated, rising to 107 kû A hinged carrying handle is provided, and which was down 0.5 dB relative to the I kHz with the input active. In the unbalanced state this is also intended to act as a tilting device filter. Bearing in mind that these checks were the impedance was, as might be expected, half when the instrument is used on the bench; made using the `just on' points of the display these values. however, when used for the latter purpose the leds having 1 dB increments, there is certainly Checking the unit for possible interaction mounting point of the handle is too far to the no cause for complaint with this accuracy. between inputs showed that interaction was at rear, with the result that it is very easy to topple Again using the 1 dB per step mode, the least 70 dB down at any audio frequency with the unit on the bench. accuracy of the display increments was found the inputs loaded from a 600 ohm source, the Virtually all the electronic components are to be within ±0.2 dB between any two indica- interaction reducing with frequency to -96 dB mounted on fibreglass printed boards, the tions, and this excellent accuracy also held for at 1 kHz at a rate of about 6 dB per octave. bottom of the case being occupied by a mother the 2 dB per step mode ! 56 0

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www.americanradiohistory.com /AMBER 4550 well prove to be a useful tool for evaluating be used for measuring sinewave frequency signals before a recording process. It may also response if the analyser's centre frequencies are have The oscilloscope output was generally satis- appropriate, but, as explained, it does not factory giving a linear output with approxi- the rectangular filter response of the very mately +5 volts corresponding to full scale expensive real time octave analysers. The fore- going applies to the peak rectifier characteristic. output as per the 2 dB per step mode. The FIG. 1 oscilloscope output was not affected by any This means that it is not suitable for noise analyser adjustments other than the input analysis or for evaluating frequency response attenuator. One snag which was noted was that using random noise, and in this respect the the oscilloscope output contained rather a lot supplied literature is misleading. From a point of mains hum. It is thought that this is due to of view of construction, the standard of the high output impedance and the proximity workmanship and design is good, but the mains of the output leads to mains wiring within the voltage selector switch requires modification for unit. The type of bar chart display created is the British market. I have also mentioned one subject to shown in fig. 1. or two other matters which could be improvement. Summary Overall, this is a very valuable tool, and is to The Amber 4550 Audio Spectrum Analyser is be thoroughly recommended for applications undoubtedly a very valuable tool for analysing where it is required to consider the possibility the spectrum of recorded levels when duplicat- of signal compression by recording media and ing tape or disc cutting. Furthermore, it may frequency sensitive devices.

ELSTREE STUDIOS of the effects sounds were shot on the spot. logue you lose intelligibility if you're not He had even managed to use train noises careful. If you know you're going to get (nobody knows where he dug them up from) greater range and keep it flat you can take more they played back academy. had no number 'He which were recorded from the genuine Orient liberties; I don't think people realise how much hesitation, he said "I want Dolby ",' Lumkin Express when it had been running. intelligibility is lost in the areas that get rolled recalls. he want Dolby as a Not only did All these rolls, of music dialogue and effects, off in academy. The music benefits a lot from mono, on optical, he decided he would want a may total 50 rolls of film. All of these cannot Dolby. The equipment doesn't add any Dolby encoded as well, which we did for stereo be mixed at once so premixes may have to be complications.' A three version him.' track magnetic recorded done to combine all the effects, or as many of Tony Lumkin again: `Others don't know the film Hills a of was shown in Beverley at them as possible, then mixing them with the what problems they've got along the road, Paramount Pictures Sales presentation towards music and dialogue. Bill Rowe: 'I try to avoid because we've grown up with it. They think the end 1973, the first ever. of doing a premix. You only do them as an they can go straight in but that isn't what it's The way the is will vary. Dolby system used operational necessity. We can do 36 tracks at all about. It needs expertise on that dubbing For the dialogue the synch track is taken from desk to make it work, to know what you can Nagra once.' a 6.25 mm machine and Dolby encoded All the premixes-dialogue tracks, effects get away with and what you can't get away before it is transferred to a roll of fully coated and music-are decoded through the rerecord- with.' A lot of them didn't have that expertise, 35 mm film. is usually magnetic After this it ing desk, mixed, encoded again and placed on he maintains. 'They could come unstuck.' post -synched at a separate recording session, a 35 mm magnetic film in three tracks: dialogue, Be that as it may the system is in use and when recording is the made on the set replaced music and effects. This is the master roll. It is working well. I've seen two movies for which by a recording better made in the quiet of a used finally to record the optical track. Sim- the soundtrack has been Dolby encoded and is then post-synching studio. This recording ultaneously, a single encoded track is made for the difference is marked. In Steppenwolf, for encoded as it is transferred to 35 mm fully transfer to the optical sound recorder, using the example, there is a long sequence during a coated film and becomes the master dialogue anticipatory noise reduction system. meal which is silent, really silent, except for the roll. The music is mastered on a 16 track Does using Dolby make things more or less music of knives and forks. Yesterday they machine, recording often at a commercial easy for the sound men. Mike Bradsell, editor would have disguised the breakfast noise with each decoded studio, and track encoded and on Stardust: 'In the editing process there are brooding cellos. Today they leave it alone. record is three on and replay as it mixed on to a things we no longer have to make allowances And you can hear every word. Stardust was from the track master. It will be decoded for. If you're planning heavy music with dia- such a good film I didn't notice the sound. multitrack machine, mixed with the other tracks and the result will then be encoded as it goes on to the 35 mm film. The triple track will be of left, centre and right signals. In the case of music for a mono film, three track music is supplied and mixed down through the dubbing Mains powered self contained units desk. The effects which are made specially for 10 OUTLET DISTRIBUTION AMP the film, post synched as the dialogue has been, GENERAL STUDIO WORK * FEEDING MULTIPLE SLAVE PA will be Dolby encoded as they are transferred AMPLIFIERS * DRIVING FOLDBACK HEADPHONES to the 35 mm film. Other effects available from Excellent distortion and LF performance with specially designed mas- a library, 'wild' effects, are generally not yet sive output transformer having separate secondaries for each 600 ohm available in Dolby encoded form but effects balanced output, giving complete dc and ac isolation £94. Also available libraries are building up their stock of encoded -kit of all electronics, excluding case and XLR connectors £55. material. There may be twenty or more effects film rolls for a sequence. STEREO DISC AMPLIFIER Collecting and assembling effects is part of BROADCASTING * DISC MONITORING AND TRANSFER the dubbing editor's job. The dubbing editor on Magnetic cartridge to balanced lines with HF and LF filtering. Orient Express was Jonothan Bates, and Bill TO IBA SPECIFICATION £95 Ring for leaflets. Rowe spoke highly of him: 'He's the top SURREY ELECTRONICS dubbing editor. He doesn't just lay tracks, he The Forge, Lucks Green, Cranleigh, Surrey GU6 7BG studies Bill Rowe said that Bates had the film.' 04866 5997 not used a single loop in Orient Express -most STD 56 STUDIO SOUND, AUGUST 1975

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Mastering Lab BUSINESS FOR ANY good and well - known cutting studio is usually so brisk that working insanely and then lying in the sun when not must seem a pretty good proposi- tion. And in the case of the Mastering Lab, add to that their almost -establishment position in LA circles, having been in their present form for more or less ten years, then commercial superstar - dom surely results. It does. In late May, the top four in the Billboard album charts had been cut in the modestly- fronted emporium near Hollywood and Gower. A rough internal guess put the average for the year at around 20 % the total American charts-one past sunny day they chalked up 26 of the 100, `but we're trying not to work that hard playback, limiters and equalisers and Keltner are playing together, now, Jesus no'. (all passive) are house designed with stereo top kit, snare and bd At the centre of the Mastering ... present results and clients list mies on each plus two additional Lab operation is Doug Sax, with are testament to their ultimate toms for the latter; that's real -time Mike Reese also cutting during my persistence at least. engineering. visit and Sandi Johnson completing The most startling things to come What about separation in such the apparent personnel: despite the out of the studio are hardly wildly a live situation? Sax: `These ubiquitous nature of the product, commercial, although doubtless stories about jumbles are just old theirs is a single cutting studio and they aren't run as any audio charity. wives' tales. On our records we the intention is to keep it that way. They are, though, in Doug Sax's get twice anybody else's separation While work may come and go, words 'a labour of love', an expres- since we don't have to trail through the gear is constant: for example, sion which echoes round LA. the console and tape machine twice speakers one -offs with added Sheffield Labs is an associated . . . and you can quote that. crossover designed by brother company, run by Doug with Separation isn't of course auto- Sherwood Sax (crossovers find partner Lincoln Mayorga, whose matically wanted -you need blend. their way to A &M, RCA, Sound playing and arrangement comple- But we don't baffle on these Factory, and Sound Lab just down ment engineering in the series of sessions and never have any the road). According to Doug, direct -cut discs which at the time troubles in fighting lack of separa- Sherwood has just about the whole of writing is a collection of three. tion. Each successive record has place attributed to him in terms of Some are out of print: the limitation used less baffling until Thelma's design credits. One relic still to two master lacquers (master and when we used none at all.' Mayorga: surviving and sounding smart is a slave cutters) holds the total run avoidance of transformers and `And I started off by using the cans 1948 Ampex, `the 23rd off the to some 50 000 copies, and this expanded over the previous 24 by and conducting from those, but for production line,' which remains with German Teldec's guarantee of Bud Wyatt. more and more tracks I just took largely unmodified and includes the 20 stampers for one mother, or In fact, more than 32 mies were them off and listened. Apart from original relays. Replay electronics 1000 to 1500 pressings each. A set up during the session: despite the drummers, I think everyone only are replaced ... Sherwood's tape master is taken simultaneously the complexities of having to cut else did too.' design. In particular, the 356 mm at the session, 'but only for evalua- four or five tracks in real time to a The music making leaps at you spool capacity is an obvious ting performance and mix, you standard demanded by the evolu- off the record - the electricity advantage with the upsurge of understand'. tion of more leisurely mixing tech- generated by needing to get 15 to 76 cm /s recording. The fourth issue is rather more niques, there was no way that the 20 minutes of music not just right Other technical areas remain ambitious. As a result of the usual sound was to be compromised but good in one take is obvious in practically as designed; when the surfeit of telephoning in all direc- through lack of facilities. Apart practice as well as theory. As Doug studio was put together, the avail- tions and the corresponding amount from the musicians rearranging Sax points out, if it wasn't such able commercial units were found of coordination, sessions were themselves between tracks in the an interesting session from the wanting ... subsequent introduc- arranged with a total of 18 top LA time given by the disc itself, an artists' points of view, there was tions such as cutting amps 'give session musicians, six classy back- amount of replugging had to be no way that they could all have higher powers, but don't give me ing singers, and Thelma Houston done, not to mention resetting as been collected in the studio at one any reason for changing my mind'. (released by Motown for the event). much eq as was necessary ... many time, with all the money in the The two old Scully lathes incor- Direct lines were taken as usual hands doubtless assisted engineer world. The contrast with the usual porate Neumann cutters but with from the studio next door, Produ- Bill Schnee in the lightning trans- rhythm plus subsequent overdub homespun old valve amps continu- cers Workshop, which is now formations required. The arrange- procedure is obvious: musically, ing to give consistently good equipped with a 32 input desk, ments themselves pull no punches. the solid gold style is for the horns service. Elsewhere, tape machine custom-made with a pathological And on some tracks both Gordon to simply tramp in at 2.30, play 58 STUDIO SOUND, AUGUST 1975

www.americanradiohistory.com expected to be a limited issue of labour of love seems to be getting SESSION LINE -UP 50 000, held down by the master- harder, although malfunction of Trumpets Guitars Jim Gordon ing limitations, which must become the photostat machine has Chuck Findley Dean Parks a classic. But even when the music occasionally hindered operations. Paul Hubinon Larry Carlton Percussion was finished and the players had Record Four should be out in July. Gary Coleman gone home, worries had only just Cost: $10 from Sheffield Labs, Victor Feldman Trombones Keyboards started. PO Box 5332, Santa Barbara, Lincoln Mayorga Dick Hyde Vocalist `We had two lathes driven simul- California 93108. UK distribution Lou McCreary Michael Omartian taneously, Mike Melvoin Thelma Houston which means that those arrangements: watch this space. Larry Knechtel lacquers are rather precious. Then Michael Thorne French horn Background singers one of them didn't process, due to Dick Perissi Morgan Aames a faulty Bass blank that had remained Myrna Matthews unseen despite our careful checking. Reinie Press Marti McCall Sax /flute Then a second side went down . . . Lisa Roberts I checked it Tom Scott Drums Jackie Ward out and it looked as if Jim Horn Jim Kellner Jim Gilstrap the record amp had gone down . . . $40 000 gone already and we start losing lacquers, that's no fun. I never felt quite that bad. 'I came in the next morning, having told Lincoln something was going wrong. Tried the lacquer again beside the tape avoiding the disc playback . . . the tape got blown off the tape machine. You Around the receptions know, that's the only time the TO THE INN On the Park for the playback's ever gone down, the arrival of Mr Evel Knievel, singer, first failure in eight years ... you motorcyclist and sometime rocket get so used to functioning one way, pilot. Best freeload since they you get conditioned to think it's launched the Good Beer Guide one thing. It was my birthday, some weeks back (same pr outfit too.' incidentally. Full marks Brian The few pauses in this story- Cartmell of Blackpool.) Scored a telling were interrupted because the brace of Ips, three posters and a T liquor store came on to discuss the shirt-a bit on the small side but order. Yes, it was to be champagne, I've asked them to change it. 11.00 am sharp, cold. Hey and I The record? Robert Craig can get Mouton Rothschild cheaper Knievel, 35, from Butte, Montana from this other guy in Hollywood, should stick to what he knows best, what's with you? breaking bones-more than 50 so Sheffield Labs' fifth project was far. Over to the man from the under way, a direct -cut recording BBC: `Is it true, Evel, that you of Lincoln playing the complete have a death wish ?' Mr Knievel: Chopin preludes, Brahms Op 119 `Bullshit. I enjoy life to the full (three Intermezzi and a Rhapsody) and want to make the most of it.' and obscure Prokofiev piano Fair enough squire, but please arrangements of a waltz from War don't make any more records. and Peace and a Contradance from Lermontov; he was abstaining from To the Manchester Square EMI the party until later. hq for the launching of something The expression, not mine, is a shade on the progressive side, an `state of the art, 30 years ago'. album of songs from the tv series Well, perhaps a little better. It's It Aint Half Hot Mum. Impressive generally called purist technique. impromptu performance of One stereo mic leading directly Whispering Grass by Windsor from the Producers Workshop Davies and the miniscule Don through unbalanced lines directly Estelle - after consuming large into the lathe. The only transfor- quantities of a beverage made from mers in the signal chain are then grain. I'm told the dynamic duo those in the cutting amps, at which are now doing cabaret in Jersey. point perhaps you can start Go easy on the cheap booze, chaps. quibbling about the drive coils. Lincoln: `Habit dictates that you To the Churchill Hotel to wel- go to tape, even if there's no editing come Mr David Gates. Best gin along with musicians that they complaining about the slow, boring to be done. Certainly, we're not and tonic of the week -a handsome might last have met last month, to sessions they were having to endure. expecting a flawless record, but at measure of Gordons and not too music that they've just seen for the So: both music and technique least it should be something of a much fizz. Nice one, A &M. first time and don't give anything coincided successfully, without un- piano sound. And it's good to do Mr Gates, the denim -clad pr for. When rhythm and brass are due compromise. To say that the the music like this.' man told me, was giving interviews playing at each other across a session arrangement had to be Future projects include further upstairs and did I want to take a crowded room, there's feedback tighter than usual is something of piano from Lincoln, with other turn after the man from the Daily that used to be there in the good an understatement, and technically ideas in the melting pot. Glyn Mail? Sorry, David, time was old days which we've got accus- ... the only limiters in circuit were Johns threatens to take up his running out and here comes that tomed to missing now. Apparently on Thelma Houston and Reinie standing invitation to organise a waiter again. the players spent the next few weeks Press's bass. So the result is session there. In the meantime, the Freeloader 59

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Single discs, I -20, Mono or Stereo, delivery 4 days 25 to 1,000 records Advertisements for this section must be pre -paid. The rate is 10p per word, minimum 1.20p. Box Nos. 25p from your tapes. Quantity runs PRESSED IN VINYLITE IN OUR OWN PLANT. extra. Semi -display rates on application. Copy and remittance for advertisements in SEPTEMBER 1975 Delivery 3-4 weeks, Sleeves /Labels. Finest quality issue must reach these offices by 16th JULY 1975 addressed to The Advertisement Manager, Studio NEUMANN STEREO /Mono Lathes. We cut for Sound, Link House, Dingwall Avenue, Croydon CR9 2TA. many Studios UK /OVERSEAS. SAE list. NOTE: Advertisement copy must be clearly printed in block capitals or typewritten. DEROY RECORDS Link House, Dingwall PO Box 3, Hawk Street, Carnforth, Land. Replies to Box Nos. should be addressed to the Advertisement Manager, Studio Sound, Tel. 2273 Avenue, Croydon CR9 2TA, and the Box No. quoted on the outside of the envelope. The district after Box No. indicates its locality.

STUDIO FACILITIES Roger Squiic Studios *Fanfare Records. Tape - disc pressings, demo's, masters, any quantity. Studio /mobile specialist recording studios for sound commercials and Neumann disc cutter. S.A.E. brochure. 1 radio programmes: contact Tony Newman orJayne. Broomfield Close, Rydes Hill, Guildford. Tel. NW8 6JN. Tel. 01 -722 8111. 0483 61684. 55 Charlbert St, London,

* Revox A77 sold, services, modified. Full WOLLENSAK 2770AV range of modifications that only we carry out. CASSETTE FAST -COPIER Ring 01 -586 0064, Radio Recordings. SCS Appointed Main Dealers RAC MIXERS Demonstrations Personal Service Maintenance mixers for groups, P.A., Cassette Fast- Copying -Short or Long Runs Custom -built 14/.0076 x 2 braided hospital broadcasting, recording, discos, etc. *Ten different colours of Full Information on Request mic cable in stock. 45ín. spring tensioned mic RAC plug -in audio modules for building SOUND CASSETTE SERVICE (SSI) arm, fin. thread for stand adaptors, designed for PO Box 2, Gerrards Cross, Bucks SL9 8EG your own mixers. D202 etc. Heavier springs for Neumann mics. Tel: 02813 84409 Sony, Akai, TEAC, Tandberg, Marantz, Lux, Radio Recordings 01 -586 0064. Nikko, Dual, Quad and Armstrong dealers. Shure, Calrec, AKG mikes and stands, etc. SOWTER TRANSFORMERS APRS Manufacturing members. FOR SOUND RECORDING AND REPRODUCING EQUIPMENT We are suppliers to many well -known companies, RUGBY AUTOMATION CONSULTANTS MICROPHONE PREAMPLIFIER studios and broadcasting authorities and were estab- Small pc board (70 x 90mm) accepting two 30 -600 ohm lished in 1941. Early deliveries. Competitive prices. 19 Freemantle Road, Bilton, Rugby, microphones (balanced inputs) and feeding loads down to Large or small quantities. Let us quote. Warwickshire CV22 7HZ 5 Kohm. Board plugs into 12 -way gold edge connector E. A. SOWTER LTD. Manufacturers Designers Tel. 0788 -810877 (Rugby) (supplied) and has presets for gain. Professional specifi- Transformer and cations. Supply +24v but will adapt for 10 to 40 volts. 7 Dedham Place, Fore Street, Ipswich IP4 IJP Call, write or phone us Board built and tested, 2 channels £37. Kit E29. Telephone 0473 52794 PEAK PROGRAM METERS TO BS4297 also 200 kHz version for high speed copying: Ce -Court Electronics are subcontractors to the *County recording service stereo and mono Drive circuit, 35 x 80mm, for I ma L.H. zero meters to Electronics Industry and lacquer discs from your tapes. BBC ED 1477. Gold 8 -way con supplied. Established in 1973 we have achieved a high masters E17. Complete kit E12. Built and aligned reputation for quality and reliability Telephone Bracknell 4935. London Road, ERNEST TURNER PPM meters. Below scalings stocked Binfield, Bracknell, Berks. Type 642, 71 x 56mm E12.60; 643, 102 x 79mm £15.00; Facilities are available to undertake the following TWIN MOVEMENT, scale 86 x 54mm E37.00. *J & B Recordings. Tape to disc. 12in. L.P. P C B ASSEMBLY £3.60.7in. 45 rpm £1.50. E.P. £1.65. Pressings - stereo /mono. Tape Copying, 14 Willows CABLEFORMING Avenue, Morden, Surrey. 01 -648 9952. WIRE WRAPPING CONSOLE & RACK WIRING *For hire Revox A77 (HS+LS, NAB +CCIR, FREQUENCYUENCY Vari- Pitch, Vari -Speed etc), AKG, BX20 SHEET METAL WORK Quad 303, Revox A78, Spendor speakers, SHIFTER Prototype production Teac four channel, mic stands, etc. Radio FOR HOWL REDUCTION Recordings 01 -586 0064. Please contact Mr S.F.Caldecourt PUBLIC ADDRESS SOUND REINFORCEMENT Ce -Court Electronics In any public address system where the microphones and Cambridge Trading Estate in the same vicinity acoustic feedback loudspeakers are Hanwell. London W7 3PA (howl- round) occurs if the amplification exceeds a critical value. By shifting the audio spectrum fed to the speakers Telephone 01.567 9672 3 ALLINGTON by a few Hertz the tendency to howling at room resonance AUDIO DEVELOPMENT frequencies is destroyed and an increase in gain of 6 -8dB is possible before the onset of feedback. Manufacturers of MIXERS SHIFTERS IN BOXES with overload LED, shift /bypass connector and housed in strong 794 A2 Mansfield Road switch, BS4491 mains diecast boxes finished in attractive durable blue acrylic. FOR SALE-TRADE Nottingham NG53GG Jack or XLR audio connectors. Type A B C Tel: Nottingham 69514 200Kohm 200Kohm IOKohm Balanced Input impedance TYPE 3678. Our Output impedance 2Kohm 20or600ohm 20or600ohm BAL SOWTER TRANSFORMER E58 f68 £84 latest production. PRICE 600 ohm, 200 ohm and 60 ohm SHIFTER CIRCUIT BOARDS FOR WW July 1973 article. Primary windings for from 2 K ohm to 10 K ohm. Complete kit and board f24 Including p.s.u. and with Secondary loadings Sound Communication use our open reel Frequency response plus/minus #dB 20Hz to 25KHz. *For Board built and aligned f31 mains transformer box, 33mm mono /stereo cassette copying service. A DESIGNER APPROVED Contained in well finished Mumetal and diameter by 22mm high with colour coded end leads. prospectus describing our other services is Low distortion. DELIVERY (small quantities) EX available on request. Sound Communication SURREY ELECTRONICS STOCK. HIGHLY COMPETITIVE PRICE. FULL (Publishers) Ltd., Field House, Wellington The Forge, Lucks Green, Cranleigh, Surrey GU678G DETAILS ON REQUEST. (STD 04866) 5997 E. A. SOWTER LTD., Dedham Place, Ipswich Road, Dewsbury, West Yorkshire WF13 1HF. CASH WITH ORDER less 5','(, U.K. post free, add V.A.T. IP4 IJP. Telephone 0473 52794. Tel. 0924 469436. 60 STUDIO SOUND, AUGUST 1975

www.americanradiohistory.com FOR SALE-TRADE SITUATIONS VACANT TOP RECORDING STUDIO (Continued) Requires experienced maintenance engineer. Please reply in writing to *West End Audio Visual Company require a technician for studio, presentation and pro- Miss Lee Packham jection duties. Sound knowledge or repairs and 8 -IO Basing Street, LONDON W.II maintenance and driving licence an advantage. Mixers? Salary negotiable. Tel. 01 -580 3184. zero 88 WANTED *Lee Electronics. The Tape Recorder and AUDIO MODULES Hi -Fi Specialists wish to purchase good quality DISC CUTTING AMPLIFIERS Tape and Hi -Fi equipment for cash. 400 offer high quality at competitive price WANTED Edgware Road, W.2. Phone PAD 5521. *BOARD Contact Richard Brown at Zero 88, NEUMANN Type LV60 Canadian company in market for used 16in/4 sub /8 mon or 16in /8 out mixing 115 Hatfield Road,St.Albans,He Valve Power Amplifiers with GV2a Feedback console. Neve, Triad or other reputable L14JS Tel.63727 Amplifiers separately or in VG I or VG2 rack equipment only. Contact Peter Alves, c/o or complete mono lathe. Unison, 1310 Rue Lariviere, Montreal, Quebec, Please reply to: Canada. Phone area code 514, tel: 527 0559. & H p.a? Mixer? GERALD *H Band in need of class REYNOLDS bargains. Caterham (22) 44804 after 7.30 p.m. Hermes Development Company Ltd., *Audiofact No.1 ! ! You can build 8 Cathedral *Recording and electronics enthusiast requires Complimiters into your mixer for less than 38 Handsworth Wood Road, studio equipment. Anything in the class of Birmingham B20 the cost of the one medium price competitor - 2DS. uneconomical to repair or completely u/s. and they perform. We also manufacture a or phone 021 -523 7307 Limited cash available. Phone Hay -on -Wye range of high quality audio modules. S.a.e. 556 after 6 p.m. or write to Paul Elkington, 28 details. Cathedral Sound, Fourways, Morris Gipsy Castle Estate, Hay -on -Wye, Hereford. Lane, Halsall, Lancs L39 8SX. Tel. Halsall BTR2 handbook, (0704) 840328. *EMI buy or hire. A. Berry, 18 Camrose Road, Ely, Cardiff CF5 5ER. *35mm projection gear bought and sold *Tektronix power supply/mainframe PS503/ Contact Leslie Bradley, 021 -353 3171. TM501 + e 20V + e 400mA 5V supplies, SOUND ENGINEER new £180. Tektronix triple TM503 mainframe Experienced for TM500 modules, new £100. Tel: 359 0051. man with high standards required in the public address and sound recording field- knowledge of electronics, tape editing and recording would be useful for asset. Smart appearance essential -reliable driver -salary negotiable. FULL FOR SALE -PRIVATE Full written details to: Managing Director, INFORMATION Griffiths Hansen (Recordings) Ltd,, PROFESSIONAL 12 Balderston :Street, London WIY ITF RECORDING STUDIO ON selling 8 Track and 4 Track machines with Desk Patch Bay and associated equipment ADVERTISING at a very reasonable price. Phone 01 -437 6255 IN ROYAL HOLLAWAY COLLEGE (University of London) *Otari DP 4050 -OC 3.75 x 6 Cassette Dup- Egham Hill, Egham, Surrey licator, A5 new£2000 o.n.o. Tel. 01- 731- 4436/7 STUDIO EXPERIENCED LANGUAGE

LABORATORY TECHNICIAN SOUND BUSINESS (Grade 2B) OPPORTUNITIES Required as soon as possible. Salary TELEPHONE on the scale L1,86042,187, plus I London allowance of £260 a year. 0 -686 -2599 Applications stating training and INDIE. PRODUCERS MAKE MONEY experience together names RECORDS available and wanted for pressing /distri- with the bution deals, U.K. and world -wide. State cash advance and addresses of two referees and ask to speak to and precentage wanted or leave open for negotiations. should Do NOT send tapes or discs until asked. Details only be sent to the Personnel Officer as to: Gavin Green, Executive Producer soon as possible from whom further TONY NEWMAN G.G.A. -INTERNATIONAL details may be obtained. Casa Mimosa, STA EUGENIA, Majorca, Spain

61

www.americanradiohistory.com Magnegraph Recording Company Ltd.

SITUATIONS REQUIRED

I am an electronics design engineer

I have worked mainly on synthesisers, instrument processors and automated Quadraphonics

I am experienced in analogue and digital design

I use advanced designs combined with "state of the art" technology Acoust ical Manufacturing 39 Koss Electronics .. 47 A.K.G. Equipment Ltd. .. 43 Lee Engineering . 55 I am familiar with every stage of producing Alice (Stancoil) Ltd. .. 37 Macinnes Labs Ltd. 6 equipment Allen & Heath .. 51 Magnegraph .. 62 Allotrope Ltd. . .. 34 Magnetic Tapes Ltd. .. 10 Audio & Design Recording 29 Mustang Communications 8 19 I am used to working long and difficult hours Audio Developments 55 Neve, Rupert. & Co. Ltd. Baileys .. 53 Philips .. .. 41 BASF .. 23 Radio Recordings .. .. 53 I want to earn lots of money Bauch, F. W. O., Ltd. 7 Raindirk ...... 53

Cadac (London) Ltd. 2 Revox . 64 Capitol Magnetics .. 33 R.E.W. Audio Visual Ltd. 9 Why not write to me: Ce -Court Electronics 37 R.S.D. Systems . .. 53 Communications, Accessories Scenic Sound Equipment .. 8 & Equipment Ltd. .. 36 Scully'Metrotech .. .. 31 Exposure Hi -Fi .. 35 Sescom Inc...... 29 TIM ORR Ferrograph Co. Ltd. . 10 Shure Electronics .. 11 Future Film Developments. 54 Soundcraft Electronics Ltd. 27 22 Mapesbury Road, Goldring Ltd. .. . 45 Streetnoise Synthesisers . 51 Grampian Reproducers Ltd. 6 Surrey Electronics .. 30,56 London NW2 Griffiths Hansen .. 37 Tannoy .. 29 Hampstead Hi- Fidelity .. 15 Taylor Hutchinson Ltd. 37 Howland West .. .. 51 Teledyne Acoustic Research 45 Icelectrics Ltd. 27 Triad 57 Ind. Tape Applications 4, 5, 63 Turner Electronic Industries 8 Klark Teknik Inc. .. .. 38 Tweed Audio .. .. 57

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Please use this coupon for your private sales and wants. Rates 10p per word. Box Nos. 25p extra. To: Studio Sound, Classified Advertisements Dept., Link House, Dingwall Avenue, Croydon CR9 2TA. Please publish the advertisement indicated below for insertion /s under the heading

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\Voodchester, Published by the Proprietors, Link House Publications Limited, 10 -12 South Crescent, Store Street, London \V.C.1, and printed by Arthurs Press Limited, Stroud, Glos. GL5 5PB.

www.americanradiohistory.com ITA Britain í Leading Distributor EVOX R E\/OX R A-7CC SER - The new big Revox - ideal for all studio requirements. Highly sophisticated design features include servo tape tension, full deck logic, crystal controlled servo electronics, 3 speeds, tape footage counter. Immediate delivery. £569 * r -7 £306 + A? R E\/OX A-77 S ERHS Mk4

The famous A77 has been consistently improved over the past 8 years and is now available in the latest Mk. 4 version. The wide choice of specifications includes versions for duplicating and logging applications. Backed by UK's fastest service. Hire service. Check cur prices. Immediate delivery.

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5 Pratt Street, London NWT' OAE. Industrial Tape Applications OT Tel: 01 -485 6162 Telex: 21879 www.americanradiohistory.com Your tape system When you play it later, will it still sound the The tape equipment of your system same? How to is your musical memory bank. It is At first sight this could seem an the one area where only the best unnecessary question. It's not makes sense. Choose carefully, though. In the course of time a high select a recording instrument that fidelity enthusiast upgrades one or neither adds nor detracts from the more units in his system. keepthe With time, rising affluence plus sound you put into it. Few machines really meet this advancing technical innovation in requirement. The Revox A77 does - all aspects of audio, will bring and by a safe margin. better reproduction within the musical scope of all. Your tape recorder and your money The recordings you make A truly professional quality tape that unit is your wisest audio now could, therefore, sound even investment. It will last for years better in the future - when, as excellence and years. finances permit, you add a better amplifier or loudspeaker to your Witness the number of Revox equipment. machines built more 20 than years Conversely, a poor recording ago that are still in service ! It's surprising made now will sound really inferior you've hardly then, that Revox when exposed to more exacting recorders command very high playback. prices second or third hand - if you With the Revox A77 you will can find them available ! retain the excellence of every already Revox owners seldom change - recording to enjoy now other than to a later model Revox. -and perhaps appreciate even more in It's also interesting to note that future. our warranty records show on the that So visit your nearest Revox paid for: average our users have bought 2 or 3 Dealer for full information and a ocher makes before choosing demonstration. Revox. Then we read the lament "I only wish I'd bought a Revox sooner."

Record it on a Revox A77

R EVOX

Revox C. E. Hammond & Co Ltd; Lamb House Church Street London W4 2PB, Revox Corporation, 155 Michael Drive Syosset N.Y. 11791 U.S.A. © Admark International Revox Corporation 3637 Cahuenga Boulevard West, Hollywood California 90068. The illustration contains optional extras. Revox International: Regensdorf 8105 ZH, Althardstrasse 146 Switzerland. BHE

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