Behind The Scenes (Feb. 1970)

by Bert Whyte

My involvement with four channel stereo gives me a distinct feeling of déjà vu ... as well it might, since there are so many parallels between four- and two-channel stereo. But there are differences, there are dissimilarities between the two, which pose some formidable problems.

As was the case with two channel stereo, there is a great deal of experimentation to be done in the matter of microphone placement before we can optimize this parameter of four channel sound. Of course, it goes without saying that microphone placement before we can optimize variables . . . hall acoustics, individual engineering and recording director preferences, the special demands of certain repertoire . . . that it is unlikely there will be a set inflexible standard. But we must at least have a guideline which intelligently used will provide some reasonable standard of rear channel information.

It is also highly probable that those engineers who make the most successful four channel recordings will have modified their recording techniques even in respect to their handling of the front channels.

They will have embraced new recording disciplines in which they think of the totality of the four channel medium, rather than the front and rear channels as separate entities. This was one of the problems in the early days of two channel stereo ... many engineers accustomed to monophonic recording couldn't orient themselves to stereo . . . they found it hard to "think stereo." In fact you would be amazed by the number of the engineers in those days who thought stereo was "stuff and nonsense!" Experimentation with mike placement naturally means live recording . . . and here is where the problems begin. One might safely assume that a typical professional classical recording session would be the best place for four channel experiment, and for the most part this is correct.

However, everyone on the session is always aware of the giant taxi meter ticking inexorably . . . the staggering cost-per-minute union rate of the musicians . . . and if things aren't going smoothly, the four-channel experiments would have to be abandoned. It is still a two-channel market and that comes first. The alternative of course, is a situation where one can experiment without the terrible pressures of a commercial session. This involves many factors and unfortunately it is going to be a more complicated procedure than it was in the early days of two-channel stereo. For example, there is the matter of the two rear microphones.

In 1951 when I was recording stereo with Maestro Stokowski, the recordings were of actual concerts. Whenever possible I hung my microphones, but often had to use mike stands and booms. This did not too greatly discommode the audience ... the mikes blocked very little in the way of sightlines and the cables snaked along the foot of the stage to one of the wings where I was ensconced with my recording equipment. Monitoring was strictly via earphones. As you can imagine, if you tried to do the same thing today for a four-channel recording of a concert, unless you could hang the rear mikes you would he out of luck as the hall management almost certainly would not permit the placement of mike stands and booms among the audience at an appropriate place in the hall. Over-riding all this would he the matter of union clearance to make the recording. Since what we were doing was strictly experimental and non-commercial, Maestro Stokowski was able to arrange clearance with the local involved. What would happen today is a matter of considerable conjecture.

Well, no matter. If we are to learn anything about this new medium we all must experiment. I have the big Crown four channel recorder and ancillary equipment and I'm ready to go! So where do we conduct our experiments? If you are fortunate enough to be near a large city or live in one, the blessed musical amateurs are the answer. In New York, the suburbs are quite well endowed with amateur symphony orchestras ... community orchestras with as many as 80 members.

There are choral groups galore . . . the colleges and universities have many musical organizations of various types and sizes. In the city itself, there is almost an embarrassment of musical riches in the large churches. As I write this in early December, the churches are offering Bach Cantatas, the Bach "Christmas Oratorio," the "Messiah." Mendelssohn's "Elijah," the Poulenc and Vivaldi Glorias, Kodaly's "Te Deum," numerous organ recitals and much more. Some of these productions are quite modest with little more than piano or organ accompaniment. Others have brass ensembles or chamber orchestras. Still others have elaborate presentations with full orchestra and some well-known soloists. Okay, so these groups don't exactly sound like the Philharmonic and the Westminster Choir! Some of them are surprisingly polished performers and when all is said and done, they are more than adequate for the experiments. Getting permission to record these various groups ranges from dead easy ( especially if the director of the group is a hi-fi nut) to in some cases impossible, due to the presence of some union musicians within a particular group. It is a very hidebound attitude because for one thing the group is not good enough to compete commercially with the great orchestras and choruses. For another thing, the union musicians ultimately will benefit from four channel sound when it eventually supplants two-channel stereo, since all of the symphonic literature including all the old pot-boilers, will have to be newly recorded for the four channel medium.

My experiences in recording two-channel stereo with organizations of this kind has been generally good with amicable relations and polite co-operation.

Once you have decided what groups you would like to record, there is a preliminary task to take care of before asking permission to record. You must visit the hall or church where the groups are to perform and check the acoustics.

Churches are rarely "dry" acoustically, but many halls are quite "dry" with reverb periods so short that they would be useless for four-channel recording. Or there may be other acoustical problems like severe slap-back, too long a reverb period, multiple echos, bass attenuation, and so on. No use trying to record four channel stereo in a poor acoustic situation.

Assuming a good recording locale has been found it is now necessary to face the fact that you probably won't get permission to place your rear mikes among the audience at the actual concert. Even if you could, the location you choose probably wouldn't be right and you could hardly change the mike positions during the concert. After all, the idea is to experiment, right? Thus we must accept the idea that the best time for our experiments is during rehearsals. Then we can make all the changes we desire. I personally plan to attend two rehearsals .. the one before the final and the final rehearsal. In this way I may find a mike placement that seems to have possibilities, and then if I am lucky, I may get permission to hang the mikes in that position and thus record the actual concert. If this is not possible, the final rehearsal will still furnish sufficient data. Since four-channel tape can be spliced as easily as two channel, a skillful editor may be able to put together a complete performance.

We're making progress, but alas, this business of four-channel recording is quite cumbersome. For example, let us assume we are in a good hall at a rehearsal. Your front mikes are in place and the rear mikes some distance down the hall. Ideally, to monitor the four-channel sound you will be in a room off to the side of the hall, or perhaps behind the stage. To reach this room from the hall you may need as much as a hundred feet of mike cable for each mike. You can't monitor in the hall with loudspeakers, hence the long cables. In the room you will have your four-channel recorder, two stereo amplifiers, two loudspeakers in front of you, and two in back of you. The room will have been heavily damped with rolls of builder's fiberglass insulation ... we want to hear the acoustics of the hall with a minimum of interference from the room acoustics. Unless you are rich enough to have an intercom system or closed-circuit TV, you'll be working blind in the room. What comes over the mikes will have to be your cues to start recording. In the case of a concert, you'll practically have to run continuously. To cope with varying acoustics of halls our mike complement would include four with cardioid pattern and four omnidirectional, to be used in various groupings. A mike that would greatly facilitate experiments is the AKC Model C-12 which has a number of patterns remotely switchable from the recorder locale. As you can see, the recording and monitoring of four channel stereo darn near requires an expedition with pack mules! As an admittedly lazy type, the thought of all that equipment appalls me. How much easier two-channel stereo recording is! You can usually have your recorder right in the hall or church with you, albeit off to one side, your mike runs are short and oh! those lovely earphones! Surely the inventive genius of the audio industry can devise some way to monitor four-channel stereo via earphones? Perhaps two separate elements in each earphone reproducing front and rear mikes? The front sound would undoubtedly swamp the rear. How about one pair of phones on the ears and the other signals via bone conduction? You can't blame me for trying! Probably the simplest thing is to plug phones alternately between front and rear amplifiers and try to hazard a guess as to whether you have too much or too little rear information. It's worth a try although I don't really believe it will work. There are many other facets of four-channel recording that require special attention, and as knowledge is acquired we'll pass it on to you.

Because we writers for the various high fidelity publications are always in the van on new developments, such as four channel stereo, there is sometimes a tendency to forget that it takes time for these advances to reach the hi-fi public.

A case in point is four-channel sound. It has occupied a great deal of space in the press, and as a very significant step forward in the quest for sonic realism, this is as it should be. However, the cold facts are that only a miniscule fraction of the hi-fi public have even seen four-channel stereo equipment, let alone heard a demonstration of this new sound. The market today is two-channel stereo and is likely to remain so for a considerable time. The two-channel stereo medium has reached a point of high refinement with some truly sophisticated recording and playback equipment. The past several years have seen the emergence of new formats of two-channel stereo, notably the eight-track cartridge and the cassette.

In the broadest terms, the cartridge has been considered a playback medium and the cassette a recording medium. At the present time the cartridge is the champ in the pre-recorded tape market, with the cassette coming up fast. The advocates of the cassette are quick to point out that it has now developed a solid market for pre-recorded tape and at the same time retaining its recording ability, and they see in this the eventual demise of the cartridge. Only time will tell if they are right, but there have been some developments in eight-track cartridge recorders which may cause the cassette people to revise their timetables. The cartridge recorders have generally been maligned because of the difficulties inherent in the endless loop format. Their critics point out the lack of fast forward and rewind, the inability to spot specific selections on the tape, their alignment problems with the very narrow tracks, and so on. While the cartridge will probably never equal the cassette for ease of recording, there now are eight-track machines with fast forward and a magnetic coding system exists, (though not yet in use) which is said to make spot selection on the tape feasible. As to cartridge recorders, a few of the early models suffered from a variety of ills . . . poor motion, bad crosstalk, poor timing facilities. The attraction that a good workable cartridge recorder would have for many people is undeniable. Even at discount prices the average cartridge is over four dollars and the motorist who has car stereo has an insatiable appetite for new material. With blank cartridges costing quite a bit less than the recorded variety, they could "roll their own" cartridges with any kind of music they want from FM tuner, phono, or open-reel tapes. Furthermore, they could erase the material when they tired of it and record something new, and really cut the cost.

To be frank, I had about given up any hope that I would ever see a cartridge recorder that really worked, when I spotted a new unit at the Consumer Electronics Show made by the Telex people in Minneapolis. Designated the 811-R, it had all the amenities needed for recording cartridges, with a few new twists to ease the task. The Telex people were kind enough to send me one recently, and to put it succinctly, it works and works well. I refer you to our PROFILE on the unit in the October, 1969, issue for all the nitty-gritties about frequency response, wow and flutter, distortion, and so on.

To my ear, all parameters were "go" . . . it sounded nice and clean with pre-recorded cartridges and the same with the cartridges it recorded. In fact, when recording from a high-quality open-reel tape or good disc, the signal-to-noise ratio of the Telex recording was better than the commercial recorded product. The big problem with all these cartridge recorders is in timing the program and knowing where you are on the endless loop of tape.

The Telex has what they call a logic circuit, which enables you to either stop at the end of each of the four programs, or play through all four programs and then stop. Blank cartridges vary slightly in the length of the tape packed in the case, so Telex suggests playing through one of the programs and timing it, so you will know exactly how much total program time you have available for recording.

The main thing is to avoid cutting into program material when the head switches to the next set of stereo channels. My contribution here is that I will pass on a procedure used to record commercial cartridges. I recorded and sequenced the first several hundred classical cartridges for RCA when they first appeared in 1965.

Let us look at a typical blank cartridge.

This one is loaded with 150 feet of blank tape. At a speed of 3.75 inches per second this will give you four stereo programs each of eight minutes duration. Let's assume you are going to record a pop program from a disc which typically contains five or six numbers on each side of various times and with a four- or five-second spiral between numbers. Recorded in straightforward fashion, you are likely to cut into a selection at the program change. What you do instead is to make your own dubbing master by recording from the disc onto an open-reel recorder.

Most non discs give the timing for each number. If not, time each number you have recorded on the tape. Now add up all the times including five seconds between the numbers for the spiral. Divide the result by four, and the result is the amount of time needed to record each program or sequence. In this case, the program is longer than the amount of time available on each sequence of your 150foot cartridge. Obviously if you want the entire contents of the disc you will need a cartridge of longer duration. If you are staying with the 150-foot cartridge, you will have to eliminate some selections to make it fit. Now the best part of making your dubbing master is that you are not restricted to placing the selections in any rigid order. The thing is to manipulate the selections so they add up closest to the desired program length, in this case eight minutes. Instead of the spirals of the disc that separated selections, you are working with lengths of tape . . . pauses between selections.

These can be adjusted to bring the program to it's proper timing. For example let's say we had one selection of 2:18, another of 3:00 even, and another of 2:30. They add up to 7:48. We need twelve seconds to bring the program to eight minutes, so we add six seconds after the first and second selections. The same thing is done for the other three programs, in each case varying the length of the pauses to bring the tape into balance.

Now you have an open-reel tape 32 minutes in duration. You cue to the beginning of the tape, set the Telex to program one with the logic switch on four, start both machines simultaneously and every eight minutes you'll dub a program on each of the four sets of stereo channels on the Telex. Using this dubbing technique you will rarely have to cut into a pop selection. Admittedly, you have interposed a tape between the Telex and the source, but on a good tape machine there will be little degradation of the signal-to-noise ratio. Those who own Dolby recorders will have no degradation at all. With classical recordings, the dubbing-master technique is infinitely more difficult. All you have to work with is the pauses between movements of a symphony or acts between an opera plus all the various little pauses and rests found in classical music.

You really need a recorder with an accurate timer where 15 inches of tape equals one second of time. The only one I know of is a $6000 Studer. With this you can run back and forth on the tape looking for splice spots without losing track of the timing. In addition to all this, bringing a classical program into balance needs the services of a master splicer. You can try a classical piece if you have the patience to undertake a very tedious job.

Best thing to do is time the classical piece, divide by four and record it on a cartridge of sufficient length and grin and bear it when the program change happens to cut into Leontyne Price holding a high C. It goes without saying that if you want to use some "off-the-air" material, you can record it directly into the Telex but at the peril of not knowing a thing about the timing. Better to record on the open reel machine first and then do your editing, timing, and manipulation on your dubbing master and then dub the result onto the Telex.

I've had a lot of fun with this 8-track recorder and it is nice to be able to make up your own programs.

(Audio magazine, Feb. 1970; Bert Whyte)

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