LIVE ECHO CHAMBERS Live chambers are out of style these days. There are a number of reasons why they're not popular. Most of them are well known and sound perfectly logical, but if there's somebody out there who seriously thinks any artificial echo system sounds better than a live chamber, I haven't met him. The usual response to inquiries about live chambers is "Oh yeah, they sound great, but......." But; They take up too much room. But; There's too much noise around here But; They're not controllable like the....system. Every one of those buts is valid. But; For some years, the best vocal chamber available to the mixers at United Recorders on Sunset Avenue in Los Angeles was about seven miles away on Fairfax Avenue. Neat trick? Not really, just the same kind of 'phone lines that have been used to carry the bulk of high quality audio around the country since network radio was invented in the 20's. As a matter of fact they were so pervasive that we still use Ma Bell's transmission line standards for virtually all recording equipment. They used to be called Class A Lines. The current term is Radio and TV Broadcast Lines, and they're guaranteed out to 15 KHZ. The cost of R/TV quality lines is wildly variable over long distances, but for a run of a few miles two unbalanced stereo pairs would probably double your phone bill. Not cheap, but it's a resource. If you can get direct wiring, an old trick for monaural drive is to use two balanced pairs, and hang the drive line on one leg of each balanced pair. It's called a phantom line, and you get one free line for every line you buy starting with two at the cost of a couple of transformers per phantom. In other words 3 lines for 2 and 47 for 24. Class A 'phone lines solve the problems of available space and noisy environments at affordable cost even when nothing can be found in the neighborhood, and since a live chamber is not intrinsically expensive, the remote realie becomes a practical proposition. The question of controlling the characteristics of a live chamber is another matter. While the driving sound can be and usually is equalized to produce an echo return sound that is brighter than that of the echoed instrument(s), controlling anything much more than that is not only cumbersome but largely a waste of effort. The writer speaks from experience here. Bill Putnam once put a long, thin (but very tall) vocal chamber at one side of a control room, and hung the mike on a couple of clothesline pulleys, so he could vary the echo attack delay. As with a set of variable acoustics mechanisms in the studio room, the optimum setting was quickly determined, and the variables were let alone after that. As an aside, Bill just loved chambers, at least partly because he not only recorded the first heavily echoed monster hit (Peg O My Heart with the Harmonicats, still the 2nd best seller of all time) he owned it. It was recorded on his Record Company Licence, Universal Records, and he leased it out. Big bucks. Built a new studio with the bucks. In another case, the writer ran up a small chamber which rang about six seconds, and sounded wonderful on record work. Then we acquired some jingle clients, and stuck a cheap rug in middle of the chamber which we could unroll to pull the chamber time down to a couple of seconds on the theory that the jingle people wouldn't be able to handle a six second ringout at the end of a spot. Turned out they absolutely loved the long echo, and we just downpotted the ringout a little at the end of the spots. Either of those mechanisms could be remoted, but proved useless in the real world. In that same real world, the live chamber can't be varied for much of anything else except funny eq for effect. Questionable. Fortunately, it doesn't need much of anything else, as unlike every synthetic system with which the writer has any experience, you can feed anything into a live chamber and it'll come out sounding terrific. A live chamber loves handclaps and claves, dotes on bass guitar and timpani, probably sounds good on cannons, and damn sure sounds good on everything else. It's primary advantage is that since it's a real room, it sounds like one in a way that nothing else can. On the down side, it can't be made to sound like anything but a room, and from that standpoint it's a specialized device. In the case of a studio whose work involves extensive manipulation of material to produce sound tailored to a specific purpose, a live chamber may well be a waste of time and money. But: For studios in the business of preserving the illusion of reality, live chambers are indispensable. Motion picture work is a prime example of that kind of thing, and the film/TV people are pretty hard nosed about echo. Consider "ET" done on a spring chamber. Preserving the illusion, or "getting a good picture" of the band is the major part of music recording whether the material is extensively over- dubbed or done as live as possible, and physical chambers contribute a great deal to the illusion. Oddly enough, they are very helpful in the case of overdubs, as their uniquely uniform response to all instruments yields a consistent acoustical environment to everything fed into them, with the result that they tend to merge overdubs into the overall sound. You'd never know the dubs weren't part of the original session, especially if you put a trace of live echo on the tracks you're overdubbing. In fact, a little live echo on a CD absolutly transforms the sound. So there's a case to be made for a live chamber, and there's a way to get it off the premises. The next logical step involves construction and setup. To the surprise of absolutely nobody, a live chamber is a very live room. Actually, it's a totally live room, which makes construction a little different than for normal rooms. What's required is walls that neither absorb sound nor drumhead when driven by sound. In short, masonry. Don't panic. Masonry's cheap. Specifically, concrete block walls are cheap. The ideal venue for a chamber is a nice quiet basement with a poured concrete floor slab and a concrete ceiling. Concerning the ceiling, fat chance, but it's not essential. A chamber needs about 10 feet to handle low frequencies, but only in two dimensions, so ceiling height is not critical. 10 x 12 x 8 to 9 feet works nicely. A little bigger is a little better, but it's best not to get carried away. While chambers get longer as they get bigger, even small rooms will yield several seconds of echo time, and very large ones tend to go somewhat muddy because of air absorption at high frequencies. It comes down to a matter of volume, and 800 to 1600 cubic feet appears to be optimum. Since it is the function of a chamber is to generate standing waves, the normal rules of acoustics don't apply. For that reason the actual shape of the room is immaterial. I recall one that was built into the space left under a staircase. It was short, but the sound was first rate. Square, cubical, triangular and round rooms all work equally well, except for placing equipment. Assuming stereo, that could get pretty weird in a triangular space. If a concrete ceiling is not available, 1 inch Lamiboard (a heavy form of particle board at 200 pounds a sheet) will do, as will sandbagged solid 2 x 4's on edge. The primary thing is to prevent vibration, which eats energy and therefore cuts down the chamber time. Concrete floor slabs wick up moisture from the ground, so the floor slab must be waterproofed or the chamber will be damp forever. If there's a question of ground moisture and/or wicking, lay a couple of sheets of plastic food wrap on the slab for a day and see how much moisture accumulates on the underside. You might be surprised. A proper door in a chamber is hellish expensive, and not really needed. A more practical approach is a 3 foot square hatch with a door made of 2 inches of particle board. Glue up two sheets of one inch board and use bolts to mount the hardware. Forget screws. They won't hold. The hatch should be airtight to keep outside sound out of the chamber unless it's in a dead quiet area. If it's really tight, you can get away with an amazing amount of outside noise. This is, after all, a soundproof room with the mikes normally sloped off below 200 HZ. The only time I've had noise problems with a chamber was an oversized item that sat about 100 yards off lake Michigan. Storms caused enough ground vibration so that we had to mount the thing up on bridge pads. With walls and ceiling in place, waterproof the inside with one of the various masonry waterproofing paints to force the masonry to dry to the outside, and finish the inside with Portland plaster. That's the stuff used in bathrooms you can't drive a nail into, because it's not really plaster. If it were, the shower steam would take it out. Portland plaster is actually fine grained concrete, and it's hard as rock. It is also the equivalent of terrazzo or marble, with virtually no sound absorption at all. Given this construction and finish, the chamber should come up at ten to twelve seconds inside, yielding about half that on record. Keeping in mind that it's easy to shorten an existing room but very difficult to lengthen one, go the whole nine yards and get the maximum ring for starters. Equipment; Neither speakers nor mikes are critical for a chamber, although the mike amplifiers had better be as quiet as possible since the mikes are working at levels down to no sound at all. The speakers and amps should be capable of handling 100 watts or more, partly because of the top end equalization normally set into the driver line, and partly because the chamber's signal to noise ratio depends on your being able to drive it to fairly high levels. If you can put 110 Db SPL in the chamber you're not likely to hear anything anything with no signal, as the undriven room will be at 35 Db or so and that's a 75 Db S/N ratio. NoNoise is about 72. One very special bit of equipment is a 100 watt light bulb with a diode button under it. Keeps the chamber warm and dry. Setup; Nothing complicated here. Stick a speaker in each corner, and hang a mike about 7 feet off each one. If you want a more solid stereo center (and the chamber will supply one) put the speaker-mike pairs closer together rather than increasing the speaker to mike distances. Seven to eight feet is optimum. In use, crossing the returns (left sent to right return) improves instrumental clarity a bit, and makes the overall sound even better. Finally, a live chamber will do a lot for the sound of most studios, doesn't cost as much as might be thought, and if there's no room on or near the premises, can be remoted to any reasonably quiet space available using high quality telephone lines. The competitive advantage is undeniable, and the project is worth consideration. -30- 1915 words