Chamber Made

How to build a natural space for reverb effects in your studio.
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These days even the most basic processors offer a wide variety of reverb options at the touch of a button. Years ago, however, the vast majority of recording engineers were wont to create their own reverberation effects using reflective rooms known as live echo chambers. Deceptively small (anywhere from 10 to 15 feet long on average, with a low ceiling) despite their enormous sound, echo chambers aped the kind of naturally occurring ambience heard in large concert halls. For years studio technicians would remedy a case of the dries by recording singers in adjacent stairwells or even bathrooms. By having a chamber on the premises, though, engineers could count on a dedicated, controlled space solely for the purpose of adding echo.

Rather than placing the performer inside the chamber, the engineer would send the signal from the console to a loudspeaker situated in a corner of the room. A microphone positioned at the opposite end (in order to maximize the echo effect) returned the reverberated sound back to the console, where it was then mixed with the original untreated signal. Adjusting the amount of reverb was simply a matter of increasing or decreasing the send or return signal, or even moving the microphone closer to or farther away from the speaker.

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FIG. 1: An unfinished basement is an ideal place to build your own echo chamber.
Illustration by Dave Simons

What is the hallmark of old-school echo? For one thing, it tends to be rounder and fuller (listen to any vintage jazz or vocal recording for proof), with none of the telltale crackling decay typical of inexpensive modern reverbs — in short, it sounds more like a real room. And because echo chambers were built by hand, history buffs can often tell where a song was recorded just by the sound of the chamber — Roy Orbison's “Oh, Pretty Woman” (Monument Studio, Nashville) and Steppenwolf's “Born to Be Wild” (American Recorders, Los Angeles) are just two examples of distinctive live echo in action. That concept caught my fancy, and not long after I'd finished writing a book about some of that history entitled Studio Stories: How the Great New York Records Were Made (Backbeat Books, 2004), I built my own live echo chamber right off the drum room in my basement studio. Pretty extreme, I admit, but in all honesty the chamber echo sounds better than any of my digital reverbs, bar none. Most of all, it has a sound that's completely unique to this studio — and there's something very cool about that.

In reality, there's nothing all that complicated about building a chamber. The key is a hard masonry interior, and the most obvious place to find that kind of surface is the corner of a basement. Because you already have the concrete slab flooring and three concrete walls, all you have to do is put up one more wall and a ceiling, and presto — you have the framework for your chamber. (If you don't have a basement, hang on a bit; I'll discuss other options later.)

Getting Started: Framing the Chamber

I chose a remote section of the basement, far enough away from the main living space (for soundproofing purposes) yet easily accessible from the studio itself (see Fig. 1). The designated area measured 15 feet long and 8 feet high, but because of a nearby bulkhead it was only about 4 feet across. However, some very good chambers were also long and narrow. If you do it right, you can get echo in almost any size space.

Start by squaring off the chamber with a long wall made of Sheetrock, fastening the Sheetrock on both sides of the wall frame to a stud every 16 inches. If possible, angle the wall slightly inward (or outward) to create a trapezoidal space, so the sound waves can bounce in different directions. Use the Sheetrock to make a ceiling as well. For an opening, all you'll need is a simple cutout about three feet square, using a hatch made of soundboard for a covering.

Now comes the important part: making an interior that's as solid, smooth, and reflective as possible. Some people use bathroom tile, which will work great but is ridiculously expensive. The majority of chambers are composed of plaster (a bargain at about five bucks per 50-pound bag) or, specifically, portland cement plaster, which is a standard plaster cut with some cement and lime. Once it's mixed, you have about 15 to 20 minutes to hang the plaster on the walls before it turns to rock. Therefore, mix the plaster in small batches and apply it in several layers to both the Sheetrock wall and the preexisting concrete wall, smoothing each layer with a large wet sponge once the plaster begins to set.

Another old trick involves adding hard rounded corners to your chamber to help keep the sound waves moving. Some of the best chambers were actually oval-shaped for this reason. Simply attach a length of Sheetrock or plywood to each corner of the room and then cover it with plaster in several layers.

To make the interior as reflective as possible, chamber builders typically covered their walls, ceiling, and floor with several coats of shellac or even oil-based marine paint (and given the lack of ventilation, nearly asphyxiated themselves in the process). To make sure you're around to enjoy the finished product, use a high-gloss latex paint instead. Be sure to cover the inside of the soundboard hatchway as well.

Though a good extension cable would suffice, it's not a bad idea to bring some dedicated power into the room. Wiring in a combination porcelain lamp holder/outlet box, or something similar, will provide you with light as well as juice — handy should you decide to use a condenser mic, for instance.

Once completed, give your chamber a preliminary test by sticking your head through the hatch — and only your head, because your body will absorb the echo if you stand inside the chamber — and then giving a good yell and clapping your hands. If the echo decays too rapidly or the tone seems fluttery, try the following:

Click to continue reading about how to build a natural space for reverb effects in your studio.

Setting Up the Chamber

  1. Go back into the chamber and inspect for gaps of any kind, then get out the plaster and cover any potential offenders good and proper. This is crucial — in order to keep those sound waves in motion, the chamber should almost resemble the inside of a refrigerator, says producer Mark Neill, owner of San Diego-based Soil of the South Studios. “This guy once built a chamber using ceramic tile but neglected to grout between the tiles, and it was just dead in there,” recalls Neill. “The second he finished filling in those little grooves, the thing rang forever!” While you're at it, get a caulking gun and carefully seal all ceiling, floor, and wall joints.
  2. From the inside of the chamber, apply some pressure to the Sheetrock wall and make sure it's good and solid — even the slightest bit of vibration can kill the echo. If you feel any movement at all, reinforce the wall by adding extra Sheetrock screws at each stud until the entire frame is totally secure.

To generate your effects send, you'll need a speaker situated at one end of your chamber, facing into the corner (rather than at the microphone, because you want the least amount of direct signal possible; see Fig. 2). A small speaker is preferable, since speakers with larger cabinets can add absorption and also tend to produce tubbier echoes. At the other end of the chamber, suspend a microphone on a boom stand, pointed away from the speaker toward one of the opposite corners (see Fig. 3). After much experimenting, I settled on a Røde tube condenser mic for the return, because a hotter mic would increase the amount of available signal from the chamber. However, even a basic dynamic mic such as a Shure SM57 would be suitable.

Other Natural Reverb Solutions

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FIG. 2: Place a speaker near and facing into a corner of your echo chamber and adjust its position to get the sound you want.
Illustration by Dave Simons

To drive your speaker, connect a small power amp to the effects send patch of your console. From the outputs of the amp, run some speaker wire out to the chamber, punching a hole in the walls just large enough to allow the wires to pass through, and connect the speaker. Then connect a long mic cable to the effects return of your console, and run that out to the chamber microphone. Incidentally, should you want a stereo effect, simply use two mic-speaker combinations, one for each side of the chamber.

There are a few tricks you can try to enhance the sound of the reverberation. Using predelay widens the gap between the untreated signal and the “chambered” return. (In the old days, engineers used a tape machine for this purpose, but a digital delay will work just fine.) Running the return through a compressor helps maximize the ring-out, while placing a noise gate in the signal path can prevent extraneous sounds from intruding once the echo has faded. You can also equalize either the send or the return to the chamber, as needed. Hint: though the tendency is to add all effects after the fact, experts contend that you get far more echo out of the chamber when using it live.

Depending on the size of your space and your attention to detail, your chamber should ring anywhere from two seconds minimum to a possible four seconds for larger chambers (mine clocks in at around three seconds on a good day; see Web Clips 1 through 5). Some engineers insist that you have to crank the send to get the best sound out of the chambers, but this approach can obviously present some soundproofing issues. In fact, I now do just the opposite — I use only a moderate amount of send level while boosting the return (hence the importance of the condenser mic).

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FIG. 3: Point your mic away from the speaker and place it at the opposite end of the chamber.
Illustration by Chuck Dahmer

If building a chamber isn't feasible, there are numerous ordinary household items that can provide organic reverberation in a pinch. A shower stall or tiled bathroom will do, as will a concrete bulkhead, a length of metallic heating duct, or even a galvanized garbage can. Simply wire up as you would a standard chamber. Other “found” spaces include hallways and stairwells; some of the best echo on record came from such environments. You can even make a chamber outdoors — Les Paul once built one into a hillside adjacent to his home. I even know someone who converted an old concrete septic tank into a chamber (and no, it didn't sound at all like crap).

“I don't think I really got the whole picture until I had a chamber of my own that was producing a recognizable reverb sound,” says Liam Watson, owner of London's ToeRag Studios and producer-engineer for the White Stripes, among others. “It literally changed my life! The thing about an echo chamber is that until you've actually used one, you can't really understand how different the echo sound is from anything that's processed. There are studios that still have the old chambers but won't use them, even though it would only take them about half an hour to set them back up. But for me, it's been the biggest breakthrough ever.”

Naturally, it's way easier to get reverb out of a box, and like all things analog, a live chamber requires some willingness to work and experiment. But if creating sounds that aren't just like everyone else's appeals to you, then a 4 × 15 room made of plaster and paint may be a good place to start.

Dave Simons is a faculty adviser with BMI's online resource He is the author of Studio Stories: How the Great New York Records Were Made (Backbeat Books, 2004) and Analog Recording: Using Vintage Gear in Today's Home Studio (Backbeat Books, 2006).