FORCED COINCIDENCE

Since practically everybody is in favor of the popular and highly safeguarded recorded stereo sound we generally call "coincident" taken down by some combination of two microphones placed, to all intents and purposes, in the same physical spot before the music--I have already (June 1988) set out my own rather surprised reaction as a music listener.

Something, to my ear, is still missing.

What I miss, very definitely, is the first "real" stereo I heard years back, recorded with a wide separation, or spacing, between mikes for the two stereo channels. The distance varied in degree, of course (having been as much as 10 to 20 feet), yet in every case produced a complex of phase differences due to the different distances the sound traveled.

(A common balancing and adjusting device has been a third mike at the center, between the other two, which may be blended in various ways into the two main channels.) The human ear notoriously dotes on phase differences! Even if they are a serious problem in a number of aspects of audio reproduction.

This month, after a suitable lapse for mental digestion, yours and mine, I present a corroborating opinion, this from within the active audio profession.

I think I was as surprised as he was to find me agreeing with him. Are we the only two souls who have this odd feeling about current stereo recording? Could be!

If you want, then, I'm fishing around this month to see if I can't pull in a few more operators who might find the idea interesting, worthwhile, and, more important, possible in the practical sense. Instead of the coincident arrays we see everywhere recordings are made (and subsequently hear in the sonic product), once again to try the spaced array, discrete separate microphones at sizable distances from each other. And in place of the ubiquitous cardioids (for directionality), the all-around pickup of the omni mike.

Yes, the consequent phase differences, particularly the big-energy bass, must be coped within broadcasting, in LP cutting. But as noted in June, things are changing fast; an enterprising recordist who wants to take the risk can surely cope, and the more so as we get into digital and away from the limitations of the LP, the cassette (analog), and present AM/FM safety standards, if I may call them that.

This professional ally of mine goes out into the field in the most businesslike way and makes recordings or broadcast pickups, for direct and practical use. All sorts of classical music, and no doubt plenty of other kinds, including musical siblings such as band music.

Somehow or other, this guy got the urge to experiment-sort of risky in such situations, you'll have to admit.

Most engineers find it best to stick to the rules, unwritten or no, and get on with the job. Not this one. "I was so bowled over by my first spaced-omnis recording [of concert bands] that it took a couple of years for me to notice that the instruments were a little bit hard to localize precisely." That's quite a whopper of a statement. First, it says that he made a regular practice, for as long as two years, of recording bands with the sort of spaced-out array of mikes I am referring to. More interesting, he was "bowled over" by the sound he got. How's that for corroboration? But in the end, his powers of aural analysis led him to a correct conclusion, as I discussed at length in June: That stereo directionality does not primarily come from phase differences in the direct stereo signals, the pair of them, that you hear. The more specific separation, so that you can "point to" this source or that, comes mostly from volume differences, which are the mainstay of the coincident stereo approach and the reason that directional cardioid mikes often play a vital part in the coincident pickup.

My friend goes on to complete his thought: "Contrariwise, I was left so cold by my first coincident mike recording [in the small hall] that I didn't care about the pinpoint left-right imaging; in fact, it rather reminded me of 'multi-mike' techniques." (No surprise since both rely on pure amplitude differences for the stereo effect.) Now don't get hot under the collar, you proponents of the always-useful coincident systems. There are terrific recordings-right and left, so to speak-made by the enlightened and informed use of coincidence. I am merely saying that something more, very subtle yet powerful, is missing.

And my friend agrees.

"In all fairness, I have since learned how to make better single-point recordings. For one thing I always, but always, avoid using a pair of cardioids, which I did use on that [first] occasion, because with them there is literally no out-of -phase information at all, whereas some [strictly 180°] always sneaks in with the other pickup patterns. This gives the recordings at least a little bit of 'warmth' or 'depth' or whatever it is ...." This, I would guess, pretty much reflects the viewpoint of a lot of audio people who use coincident techniques with, shall I say, a small grain of stereo salt. The foot-or-so separation that I seemed to observe in Denon's "one -point" array again seems pertinent.

I should pause here to explain. My friend and ally, the above quoted, works at a Public Radio station. I have so far de-emphasized this because I believe that his thoughts and conclusions largely apply to other areas of recording. Namely, any area where an unhoked and natural all-over sound, with a natural-seeming presence in the consumer playback, is desired.

Now if I am right (out of some personal experience), local Public Radio stations, often sponsored and underwritten in part by a university or other local institution, are allowed considerable autonomy to do what they wish--and dare--with the material they put on the air. This applies not only to programming, as a matter of course, but also to the technical means used.

Some readers may remember my discussion, years ago, of the extraordinary mike pickup I saw at the Oregon Bach Festival in Eugene. Large oblongs of transparent plastic hung giddily over the orchestra's heads or were set oddly on the floor below the concert stage, aiming upward at an angle, like so many zany music stands, toward the solo singers at stage edge.

PZMs. That was Public Radio, considerably supported by the University of Oregon-station KWAX. Nevertheless, this suggested a very considerable independence of mind to me, and still does. The PZMs, prototype do-it-yourself models before Crown, have been retired, and all now is coincident. New regime, I assume.

On the other hand, the national PBS, the big network that distributes its recordings to hundreds of PBS outlets at varying times--and not, I gather, always the same network--follows a very different principle. Perhaps necessarily, to avoid (so to speak) mismatches and other local troubles, PBS sets up strict procedures, just as rigid as the network is large. This is inevitable, as all can understand. But in some opinions, it goes too far, for the sake of uniformity and safety, when subnormal intelligence is at work. (It always is.) On and off for a number of years, my own homemade broadcast tapes were aired on a fair number of individual NPR stations, sent from one to another on an extracurricular basis entirely outside the auspices of the national network. I was told emphatically that these tapes-both the content and the Canby "engineering"-would never pass muster at the national level. But local enterprise liked them, and indeed a few stations put them on the air via copies, without even bothering to ask my permission nor to tell me when. At that point, I cut off the source in a hurry. The least they could do ...! Now, every station that originates broadcasts or recordings naturally hopes to get itself onto the big NPR network, with its hundreds of outlets.

Who wouldn't? (You've heard the tag lines plenty of times, so-and-so originating in such-and-such a city.) And therefore there is a very heavy pressure, in local operations, to conform lo the national standards.

"Last year," writes my friend, "I went to a workshop given by National Public Radio ... on classical music recording techniques. Overall, it was a really excellent workshop, designed to give producers for local stations the skill to turn out tapes of 'network quality' ... My one complaint about it was the hard sell of strictly coincident miking techniques. They had set up a makeshift LEDE monitoring environment, and we made tapes one night on an 8-track machine, which allowed simultaneous recording of the same event with four different stereophonic microphone techniques. The workshop leasers all claimed to hear the most accurate representation with the coincident (particularly M-S) techniques, and did not understand my objection that depth was lacking." Words, words! What is "depth"? Not easy to say.

He goes on: "To my ears, although it was possible to figure out how far back on the stage an instrument was by its relative amplitude, ambience ratio, etc., the overall effect was still akin to looking at an ordinary photograph (or painting): You can tell that some things are nearer and some farther away, but it is not like a 3-D photograph or hologram [or reality]." In a word-mono. Is not a mono recording much like a flat photograph? Major and satisfying clues as to space and distance are there, but other clues are absent. Are they missed? That depends. Can they be provided? Perhaps--but always at some cost, variably different according to the situation. That is what we are talking about.

This man's account essentially confirms my thought, that strict coincident stereo is actually multiple mono--many different mono sounds in different directions. The real stereo "depth," the living ambience provided by variable and multiple phase differences, is specifically removed by the coincident techniques. There's still much left in sonic effectiveness. Plenty to keep us all going. Yet something more might be added, if we will face up to the problems involved.

My friend ends his comments on the NPR workshop with the appearance of an unexpected ally (not myself). Though his workshop leaders did not understand his thinking (and listening), he was reassured, later on, when he found that "They had invited a music professor who did not know much about audio to listen and give his opinion, and he preferred the spaced technique over all the others [my italics], saying it sounded the most like listening to music in the hall." Forget the old concert hall bit-as I've said, this is still the standard phrase to use when you think a recording sounds the way it ought to. But the professor used his good musical ears, and, by golly, I say he was right. Will you, the home (and car?) listener, agree with him? I expect so.

Professionals can be forgiven their wishful thinking, making things as they want them to be. Convenient and all too easy. The consumer ear, when it listens carefully, can be very objective.

I think, finally, you may understand why I have left my PBS friend anonymous. I would prefer to give his name and even address, but the man's life work is involved, and I, for one, do not wish to give him even a hint of trouble.

If he wants to promote spaced-out stereo with his own people, he should do so of his own choice, not mine. Good luck, John Doe!

(by: EDWARD TATNALL CANBY; adapted from Audio magazine, Aug. 1988)

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