How to make a bright room a little more musical

April 19, 2006 3:39 PM

Looking for techniques on how to deaden an isolation booth in which we are recording drums.

We currently have an isolation booth that has been built with no right angles in the walls. The floors and ceiling are parallel. The walls are drywall, and 7 to 8 feet long each. The ceiling is eight feet high.

We are experiencing a lot of brightness in the room when recording drums. What can we do to deaden the room in a musical way? Solutions that we could remove or fine tune as time went on would be great.

Thanks!

posted by jon_kill to media & arts (15 comments total)

I presume you're already hanging acoustical surfaces such as these...?
posted by frogan at 3:53 PM on April 19, 2006

Hang blankets from the walls? Fit acoustic foam tiles? Egg boxes? Carpet the walls?

Any of the above will help....
posted by gergtreble at 3:54 PM on April 19, 2006

homemade treatments
posted by bigmusic at 3:59 PM on April 19, 2006

I like to record drums in a bright room, but anyway...

What you probably want is a baffle. You can get one that looks like a small wall on wheels. Another easy thing is just large rectangular pieces of thin plywood. They diffuse the sound without making it dull. Move them around until you like the sound.

Here's a link I just found on studio acoustics
posted by bhnyc at 4:02 PM on April 19, 2006

The size booth you are describing is OK for spoken voice work, but is really small for doing anything musical. For one thing, with the dimensions you describe, it's going to seriously limit the creation of low frequency sound components, and this, if nothing else, will certainly unbalance your sound source. Even a 100 Hz frequency component will have a wave length of about 10 feet, which is greater than the dimensions of your booth in any axis. Drums produce significant energy in low frequency sound components, down to about 10 Hz (or over 100 foot wavelength) and the amplitudes of kick drum sounds can be overwhelming in small volume booths such as you describe.

If you can, look for a substantially larger space in which to lay down your drum tracks. Your results will be far superior to trying to work in such a small booth.
posted by paulsc at 4:07 PM on April 19, 2006

Attach a quilt to the ceiling, leaving big slack areas of fabric to hang down. I understand this prevents standing waves. I think parallel ceiling and floor is undesirable in a drum room. Better minds will weigh in on the matter, no doubt.
posted by wsg at 4:22 PM on April 19, 2006

Coats on a coat stand (they're cheap and usully available)
posted by Dub at 4:31 PM on April 19, 2006

Hey, PaulSC. I dream night and day of a larger space in which to record, and that is definitely in the plans. For now, though, we demo at home and the neighbors complain when we take the drums out of the booth. For the time being, we've decided to go ahead and record what few songs this sound suits with the drums in the booth, and then petition the building to finish up the heavier tracks.

Thanks everyone for your advice. We moved some baffly type objects in, and they seemed to mellow things out considerably, so that's good. We also played around with the mics to get it a little crisper without the harshness. It sounds pretty good as is.
posted by jon_kill at 5:38 PM on April 19, 2006

Hang duvets from clothing rails around the drumkit, and do what WSG said - duct tape something thick and soft to the ceiling. You can either cover the whole room in insulation, or make a freestanding cube of DIY baffles to surround the drums. Beanbags make good bass traps.

Paulsc, bhnyc's link appears to contradict what you suggest:

There is a common myth that small rooms cannot reproduce low frequencies because they are not large enough for the waves to "develop" properly. While it is true that low frequencies have very long wavelengths - for example, a 30 Hz wave is nearly 38 feet long - there is no physical reason such long waves cannot exist within a room that is much smaller than that.

Then it goes on to explain why in terms somewhat beyond my understanding. Carpet, apparently, is something of a no-no.
posted by so_necessary at 5:44 PM on April 19, 2006

(Dang, rendered un-necessary at the last minute. Ironic, given my alias. Happy rocking, Jon!)
posted by so_necessary at 5:45 PM on April 19, 2006

On the cheap, make some simple acoustical panels:

1. Build four or more 4 ft. x 4 ft. wooden frames out of 1" x 4"s. Make each frame 4" deep, with a 1" x 4" divider running vertically down the center of the frame.
2. From the back side of each frame, staple 3-1/2" thick x 24" wide paper-faced building insulation inside each vertical half of the frame (the paper side faces the wall.)
3. Cover the front side of each frame (and the exposed fiberglass) with a cheap open-weave fabric like burlap. Wrap the fabric tightly around the frame sides, and staple it to the back edges.
4. Use picture-hanging hardware—screw eyes and braided wire—to hang each frame on a drywall screw or box nail on the walls.

Start in the middle of each wall, and experiment a little to find the best spot on the wall to hang each frame. Build more as needed.
posted by cenoxo at 7:34 PM on April 19, 2006

"Paulsc, bhnyc's link appears to contradict what you suggest: ..."
posted by so_necessary at 8:44 PM EST on April 19 [!]

I read that, so_necessary, before I posted above, and thought to myself "This ought to be good for the AskMe contradiction mill." So here's my expanded contradictory comment, based on a bunch of time in broadcasting and studio operations.

The author of bhnyc's link proposes a thought experiment in which we create low frequency long wavelength audio waves outdoors, in what is traditionally known as a "free field" and then successively do it again in a large "room" with thin paper walls (practically a "free field") and then in smaller and smaller rooms with more and more substantial walls. And that author correctly observes that at no point is it impossible to get low frequency wave fronts generated in those increasingly constricted rooms, that somehow can conceptually pass other points in those rooms, and be sensed as sound vibrations. I agree.

What I don't concede, and what is later tacitly admitted by the author of that article is that the increasingly constricted rooms he asks us to imagine will have increasingly detrimental effects on the resulting sound, as a coherent musical experience, and he recommends trying to damp such rooms heavily and perform corrective frequency equalization on the result, for recording purposes, as his best practical strategy. And no, this isn't a case of my nearly magical ears sensing something only 1 person in 10,000 can possibly appreciate. Everybody that isn't massively hearing impaired senses this, right away, when entering small rooms. Any three year old with normal hearing can be asked to close their eyes, and enter a house from outside, and can tell you accurately when they've been carried inside, largely by the changes they perceive in the sound field of the enclosed space into which they are carried. Do the same experiment, but carry them into a large aircraft hanger, or auditorium, and they'll be less sure they've entered a structure, for lack of near field alterations in the reflected sound fields, as such large spaces more nearly approximate the "free field" experience.

The author of the article proposes that all the cancellations and reflections in rooms too small to contain unreflected long wave energy can somehow be damped out, smoothed, and otherwise made to go away by some slick placements of damping materials and/or reflective surfaces. But the fact is, in very small rooms, if you have a lot of complex sound energy being created, it's impossible to passively correct for the all the problems simultaneously, and the tendency is to massively overdamp such rooms, and then try to recover the sense of acoustic "free field" by amplification and complex signal processing. So these efforts tend to wind up sounding like room sized headphones might, in a bad dream.

About 20 years ago, academics and a few commercial companies started research into systems which used active electronics, and large speaker arrays to perform active sonic corrections in audio studios and in large concert hall and meeting rooms. The idea was to use electronic signal processing and amplification on a large scale to overcome architectural deficiencies in rooms of all sizes, and give any space a controllable sonic profile appropriate to any number of changing loads and uses. I've heard many of these efforts, and my general impression is that it is possible to sweeten a good space a bit, but still almost impossible to turn an acoustic sow's ear into a silk purse, even with the best systems and most advanced processors. The reason is simple: in a good acoustic space, sound energy decays predictably and generally smoothly, as it does in a free field, with perhaps a few easily characterized primary resonances or cancellations, and perhaps a bit of unphased reflection. Such halls or rooms can be substantially improved with only a few corrections, and performing the corrections will not generally introduce new problems.

But in very small rooms, where the physics of reflection, absorption and decay are considerably more complex, trying to compensate for the many cancellations and phase issues inherently present is practically impossible. Small rooms are generally far from "free field" situations, and to the extent that they introduce phase and amplitude cancellations of their own, they are going to be perceptually small spaces.

All this is not to say that enterprising musicians can't play with a room's acoustics, to some musical advantage. If that's what you're going for, I say have fun with it. But generally, in my experience, musicians do better, sooner, if you put them in a large quiet space, and let 'em play.

I do appreciate jon_kill's problem, and I'm glad not to be the one trying to put a drum kit in an 8 x 10 x 8 foot room, mike it, and get something coherent out of it for a recording. His problem is not unlike that of some of the people doing "live" jazz recordings in small clubs back in the 50's and 60's, where the "intimate" sound they got was primarily a pretty hot natural "presence" band around 2 to 5 KHz, created by the small band stand mike placements, and small rooms stuffed with hundreds of bodies smoking and drinking, creating a massively overdamped sound field. Something like this, or this is the likely result, if it goes well. Not a bad sound, but not the real sound of drums, either.
posted by paulsc at 11:06 PM on April 19, 2006 [1 favorite]

Another way of thinking about all this is to view car audio systems as a limit case of the small room problem. Sure, if you pump enough low frequency energy into a confined space, you will have bass.

But is it musical? Opinions vary, but mark me in the "not even close" group of respondents...:-)
posted by paulsc at 11:13 PM on April 19, 2006

Here's a good discussion on egg carton and carpet myths, and what actually what works and what doesn't. Many say that soundproofing boils down to mass and little else.
posted by jikel_morten at 7:24 AM on April 20, 2006

Okay. Some thinking out loud to cap this off.

We put some baffles in there, and the sound is actually... uh.. good. As in, I enjoy it. Would it be better if we could record in a big room? Yes. What does better mean, really?

The song we recorded drums for last night was mainly two acoustic guitars, bass, keyboard, vocals, harmonies and drums. We had imagined a dry but creaky sound for the drums. Creaky was our goal for this track, and that meant a sproingy snare drum (accomplished), a little sizzle on the hi-hat (accomplished with an Oktava 012), and some "room sound".

I'm glad we wrote this song with the drummer in the booth riffing on what we were doing outside. It tailored the sound and dynamics of what the other instruments are playing. I guess the whole thing could be summed up to a thought experiment. While writing songs, we've consistenly applied little restrictions in each scenario depending on how we were feeling that day. This drum sound (which we've learned to expand/"compress"/deaden/etc... through use of mics and their placements) is part of the restriction for this song.

The bad part is: we have five or six songs for this record that need a big drum sound. That means contacting the neighbors, buying bottles of wine, keeping an ear out for the cell phone... sigh.

We're hoping to gain enough experience and.... well, gear accumualtion, to make the jump to a larger space, at whcih point I'll be calling drummers and asking them to come down so I can just wallow in the beauty of it all. PaulSC, it sounds like you're in a similar position, and that must be great. Sigh.

Thanks for the help, everyone.
posted by jon_kill at 7:42 AM on April 20, 2006