Audio Etc. by Edward Tatnall Canby (Sept. 1975)

by Edward Tatnall Canby

NEVER CAN TELL where true binaural sound will pop up these days, for listening inside those thousands of headphones we have been buying. By the time this hits print, my latest binaural experiment will be audible to you, hopefully, right in your home. It'll get there by radio, The Bottom Line-which hasn't a thing to do with IRS Form 1040-broadcasts that were scheduled to begin, all over, in mid-August. Try your local FM schedule. We've found a way to broadcast for both binaural and loudspeakers and OK for both.

No-not stereo via phones! True binaural, specifically tailored from binaural mikes at ear distance. I've named the principle The KC Factor, for self and Don Ketteler, the sound man who got me involved and who did most of the work.

The Bottom Line is what we elders would call a rock palace. It is a big, successful, good natured place that crowds itself into a vast ground-floor cavern deep in the heart of the Village (NYC)-great, dusky spaces; tall, old-fashioned iron pillars, art nouveau style, and ex-factory, and the whole is painted a dark dun color so that when the lights go down, space becomes infinity. On the floor, a score of long, narrow wooden tables jammed around a thrust stage-the waitresses practically climb onto them to reach the customers. In there, you stay put, unless you are a table hopper. On a small projecting rear balcony, accessible by iron rung ladders, is the guts of the place, sound and light, and one of the finest, smoothest sound systems, for its size, this side of the A. and the P. Slung from the ceiling are great hulking speakers, dun-colored too, their odd-looking downward aimed slats directing tidal waves of sound to the tidal waves of young people who wave up from the waves of tables. ... enuf. It's a rock palace! Two shows a nite and jammed to the air conditioners for such acts as Manhattan Transfer (I was there-no fingers in ears and I did NOT walk out) or maybe Mike Bloomfield, David Bromberg, Kenny Rankin, Rachel Faro, the Persuasions (a cappella vocals), the Nitty Gritty Dirt Band &c &c &c. That's the unlikely mise en scène for our binaural.

Don Ketteler is a sound man who inhabits the BL platform. He had read my two "Ispy" articles (Audio, Nov., Dec. 1974), all about the Sennheiser binaural plastic head with the miniature mikes hooked into its ears, and had come up with a hot idea. His balcony, alas, is sonically defective; air ducts and the like hem him in and they make his job quite tough. Why not try a binaural head, located at a favorable listening place, and monitor the shows via binaural surrogate ears? Fascinating, but things aren't as simple as they seem in this world and that project is still hanging. Still, Don got himself an "Ispy II," (exactly like mine except, of course, dun colored) and in no time the boys were taking down binaural on a cassette machine, just to see what was what. Good, too, even unto a Vivaldi concerto playing on the big P.A. system in mono. (It sounded exactly like Vivaldi played in mono.) They did find that the best place for Ispy Il was high up on one of those iron pillars, above the audience and well removed from the stage. That was significant. Mike distance of some 30 feet or more to the nearest performer vs. maybe an inch or so for the close-up cardioids used in the regular stage show. Some contrast! Then came another and better idea.

There was already a remixed "live" tape going out to a nearby FM station which the management was planning to expand into a big-time nationwide hookup via "live" tape. Hey, why not feed some of Ispy II into the remix lines, and get binaural from the BL-on the air! No sooner thought than done, experimentally. Don had the facilities and young engineers are quick to enthuse. In short order, their cassette was taking down a mix, partly Ispy II's binaural signal from up on the pillar and partly the regular broadcast feed. Interesting.

The house P.A., you'll understand, is strictly mono, one enormous audio signal out of 16 or so mike channels combined at Don's console. The stage channels are necessarily either direct, just from guitars, etc., or via ultra close cardioid mike-otherwise FEEDBACK. Totally dead and projected directly as the "live" out-loud sound of the performers. The radio feed is separately mixed, via splitters, into an arbitrary two channels out of all of these same house channels. Note that the actual loudspeaker P.A. sound is almost totally suppressed in this sort of system. It's only for the customers.

Well, the mix didn't work out very well, and it was about this time that Don contacted me, maybe for inspiration à la Ispy. Trouble was, they found that in the phones, in order to overcome the powerful mono signal for the radio feed, the mix had to be almost all-binaural-and useless for loudspeakers. Fix things to sound OK on loudspeakers (essential for any broadcast) and there was no binaural.

What to do? Binaural old-timers will understand.

Binaural is Different. Each channel is fed exclusively to a single ear; whereas via speakers we hear each channel, each speaker, with both ears (and thereby locate them in space). That means utterly different requirements.

In mike technique. For loudspeakers, notably in pop, plenty of cardioid ultra-close pickup, for crisp definition and localization. For binaural headphone listening-distance, 'way off, via omni-mikes (seldom used in pop-the BL hasn't a single omni). And of omnis, only two, spaced a mere eight inches apart. Imagine broadcasting that!

Did I say mono, above? Don didn't get me. Wasn't the broadcast mix two-channel, for FM stereo? Well, yes, but my trusty ears heard the house-mikes' sound, two-channel or no, right down at the back of my inner skull. It was MONO. So we checked-yep. Up at remix control old Ketteler had set the multiple pan pots straight ahead, centered, in neat rows. Probably just to look nice between shows, like pens and pencils on a desk. So we had two-channel mono, to mix with our binaural signal. No wonder.

You simply cannot feed a strong mono signal like that into phones. It compresses the brain, kills every vestige of space and overwhelms binaural. (Even worse is to feed any signal into one ear and not the other. Then, all you hear is a one-eared jangle. Yet a lot of pop and even some classical does virtually this very thing, to get sounds into one speaker or the other.) All this gave me my own bright idea.

I suggested for remix we set up the panpots, just for experiment (and NOT on the air!) at opposite extremes, either all-right or all-left. Crazy, but I was getting a hunch. We would now have a feed that was not mono, not stereo, but two-channel discrete, the music split right down the middle. Could I use the binaural signal to pull these channels together? That was the KC Factor, incipient.

Via speakers this would sound incredible, as well as discernible. On phones, it would be schizophrenic.

Just what I wanted! So Don followed through. Next time I listened to his mix, things were really beginning to schizz. Via speakers, the remix feed was two separate recordings of the music, half-and-half sidewise. Via phones, it was chaos. Now we took on a new and useful tool, my handy TEAC 2340 quadraphonic recorder, so portable the boys almost didn't hail a taxi to bring it to the BL. On two TEAC tracks we recorded Ispy II from his pillar, pure binaural, plastic head and all.

On the other two tracks, we took down the bifurcated experimental radio feed, right out of the stage close-up channel. Now we could blend variably to taste, and after the fact, KC was beginning to define itself. Get the idea? Here's how. In practice, even the deadest, most-discrete pop mixdown has some sort of sonic meld to join the final channels into a unity of space and presence. Usually this is via a bit of cross-mix, live or synthetic, here and there, plus additional over-all ambience, the same. A well-recognized art, even into classical technique where ambience is already inherent in the performance. We do it there--close-ish mikes, separated, for definition. Then in mixdown an overall ambience to focus and place the whole. Standard approach.

Clearly, something of this nature would be required for a Bottom Line broadcast. My thought was to use the binaural signal for this very purpose.

We could try! All we had to do was turn on the TEAC and mix our channels to taste. It worked. At least, to my satisfaction. (Ye Editor heard it, and looked cryptic.) I was delighted, because I had a further and trickier hunch. Phones and speakers would "see" this mixed signal very differently-and to our advantage, if we played things right.

Take it from the speakers' viewpoint. To a pair of loudspeakers, Ispy II's mikes, distant and close together, are virtually a point source out in the audience, an omni-ambience mike (with, to be sure, a hint of stereo spread, all of eight inches!), which picks up not only space ambience but the sounds of satisfied customers, right down to the last bravo, which is balm to sponsors' ears. Ah yes. We needed that, and we had it. We could even bring the audience up, between musical numbers. So what could be better, for loudspeakers via FM broadcast? Now look at it from the viewpoint of the headphones, hearing the same mixdown signal. Remember the 100 percent separation. In phones, a very little binaural signal goes a long way, if you give it a chance (no mono). Why else does Mama N. give us only a few inches? All we need. Otherwise we'd have ears on stalks. We are so sensitive to real binaural signals, separately to each ear, that a tiny bit of signal in one ear, the other channel being at full level, is enough for complete binaural fusion, roundness and space-try it. Maybe 60 dB difference.

(And just try waggling the image from side to side via your volume balance control, as you can do with speakers.

Won't budge.) So-from the headphone viewpoint, a small increment of binaural signal should be enough to pull the close-up discrete signals together and add binaural space and realism. In fact-just about the amount we use to liven up the signal for broadcasting. That's the KC Factor.

You can have it both ways.

Of course, this isn't going to be a literal binaural pickup, as from Ispy's own signal up on his pillar. That's OK for phones, but poison for speakers.

What we do get via phones is parallel to the speaker sound, a synthesized, artificial but aesthetically-pleasing binaural effect, a lot better than mere loudspeaker stereo via phones, though even that often works out fairly well, as we all know. Can do better.

Get the formula, then. A generalized principle for all sorts of widely different mike situations. You start with your main or close-up signals, whatever, and give them MORE separation and LESS ambience than you want in the final mix. Then use the distant, ambient-binaural signal to pull the sound into desired focus and space, to taste. Fix things right for loudspeakers and-with the binaural signal present-the sound will be automatically OK for phones. Binaural is flexible, inside the headphones. In practice, you may not need nearly as much exaggeration as we used, but it's good to start that way, just to see how the thing works. So long as your binaural signal is (a) relatively distant, as ambience/audience sound, (b) can be used to pull together that which is overly separated and (c) add space and liveness to that which is overly dead and close, you should be OK for results. Even in classical. Lots of ambience there already, but you still can manage enough exaggeration, as per above, to do the trick. That's the KC Factor.

P.S. in stage whisper: I suspect that two ordinary omni mikes (never cardioid) placed eight inches apart and minus any head, should serve almost as well as anybody's Ispy, though less picturesquely. You can try, anyhow.

So now go out and catch the Bottom Line via your local FM. And have your phones ready.

(Audio magazine, Sept 1975)

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