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Make Your Control Room Sound Good

(And words like "translate")

by Phil Gates

Does your mix translate to the real world? Have you heard that phrase before? Perhaps so, perhaps not. But I think we’ve pretty much all experienced it. By translate I mean; Can you take something you mixed in your control room to another CD player in someone else’s house, and it sounds just as good? Did it translate to the real world? If so, then great! The next column is about Plug-ins. C-Ya! (Just kidding- Stay here!)

I used to call it being able to "Walk" your mix to another environment, and listening. Whether you "Walked" to your car, or a friend’s house was up to you.

We’ve been talking much about audio, and mixing, and gain, all very happy, and then I moved my studio…
… I moved the studio into a new place. Into an acoustically untreated room. Ever been to the Grand Canyon? Reverb, delay, standing waves, flutter, all from one handclap. Any enthusiasm I had for getting a new room just left with a heavy sigh.

I know I’m not alone. My point, in a very round-a-bout way, is if you’re having trouble with your mix not translating, maybe your mixing chops are great, but your room is killing your mix! What does your room SOUND like? Have you done anything to make your listening environment more neutral for mixing? Is it affordable? It can be. Is it easy? It can be.

Truly, I’m not an acoustic engineer. And I’m not going to go into the science of acoustics. I want to impart on you a few things to think about when it comes to your environment. After almost twenty five years of this, I’ve spent time in a few different rooms mixing.

Is your room square, or rectangular? If it’s square, pick a wall as the place to put your mixer & speakers. If it’s rectangular, use a short wall, and have the length of the room behind you.
After you choose a wall, break out the tape measure. "All things being equal" is the frame of mind that you want to have. Find the center of that wall. The speakers should be equidistant from the centerline of the wall, and your listening position should be equal distance from the speakers. (All figures are approximates) See fig 1.

If you have space between the wall and your mixing desk, then you can put the speakers in-between the wall and the desk, this can help reflections from your desk getting to your ears. See Fig 2.

Next is treating the room. There are two terms that are important to differentiate: Absorption, and Diffusion. The names kind of imply what’s going on. Absorption means the acoustic tile or foam panels will actually absorb the sound energy. Diffusion means that the acoustic tile, wood panels or foam panels are going to more evenly disperse the sound energy a room, not letting the sound gather in one place. A room may need both, and is usually suggested.

There are a few types of materials that comprise the panels. It can be acoustic foam panels, treated material, straight rigid fiberglass, or other materials. Make sure that if you use fiberglass to cover it with material to keep glass particles from breaking loose and getting on you or in gear. Even wood can be used to deflect sound.

The days of egg cartons and carpet are pretty much behind us, but if that’s all you’ve got…
There are companies like illbruk (Sonex), and Auralex that make many different solutions for acoustically treating a room.

How much should you use? Typically you want 40 –50% coverage for a control room to be well treated. You may need more or less, depending on the natural acoustics of your environment.

My room was a totally square room (pretty much the worst acoustic situation possible). I had a ton of reflections, and flutter. So I had to treat it pretty heavily.

The places to place the material are right behind the speakers for bass frequencies from the rear ports of your monitors, and on the sides of the room where the sound from the speakers will hit first. See fig 3.

The red lines are the initial sound travel. I left the rear wall untreated to keep a little live presence goin’ on. There’s a trick that has one person hold a mirror against a side wall, then move from front to rear of the room. While you’re in the mix position, wherever you can see the speakers in the mirror is a place to put acoustic panels.

In the corners are bass traps that are great for getting rid of standing waves. Which really aren’t just sound waves "hanging out" in your room corners, it’s frequencies that have collided with the reflections off of a surface, (say, a corner) so neither sound wave moves for a period of time. This can affect the frequency response of the room.

Which takes us to "how do I know what frequencies are prominent in my room?" I found a couple of shareware programs on the Apple site. One is called "Audio Test", and the other is "Audio Toolbox." I used Audio Test as a signal generator. (Although I’m sure there are plenty of other Audio testing software programs out there.) It generates individual frequencies as constant tones, on a sweep between two frequencies (from 20-20kHz), or pink & white noise generators. I used the spectrum analyzer in Emagic Logic’s EQ to see what was going on. The Audio Toolbox has a Spectrum Analyzer included if you’re audio software doesn’t have one. This is a down & dirty way to analyze your room. Place a really flat frequency response mic (or one where you know the frequency response curve, so that you can compensate for the curve of that mic) in the listening position, facing one speaker. Play pink noise through the speaker at least 30db above ambient room noise, and record it. Then play back the track through the spectrum analyzer, and look at it. Do the same for the other side. Here’s my room before treatment: (The screen readings are intentionally volume shifted to have a horizontal center-line visually for this column) See fig 4.

You can see that the room was totally out of control on the low end. After putting in some absorption materials & bass traps, and some EQ filtering, the curve looked like this: See Fig. 5.

And my square box became a room I can mix in. had I left it alone, all of that extra low-end frequency would have left my mix mixes incredibly thin. I would have easily heard what I “thought” was low end while I was mixing that really was the room’s frequency response. Then when I went to “walk” my mix, it would have sounded really cheesy, with much less bass than I had intended.

Every room is going to be different. Some rooms will sound great right away, and some rooms will need more treatment. Also sometimes, if you can listen to the faults in your room and know where to anticipate them, then you can compensate for that while you mix. I prefer to have a good sounding room, and with a few of these tips, your control room can sound better as well.

Take Care,
Phil
music@philgates.com
www.philgates.com





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