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The Stuff That Rooms Are Made On

Find out how to direct the noise inside your room to better effect


How are the acoustics in your home studio, and should you put traps down for them? John Peel stares at the four walls and suggests what to do about being dead, being live, and living with eggboxes.

THEY'RE SO persuasive, those 4-track ads. "All you need is a Funkbang 999, a mike and a pair of headphones, and you've got a complete recording studio." Which only shows that Funkbang's copywriter has never been closer to a recording studio than I have to the editor's wallet.

The truth is that all the gizmos you buy (or drool over) are only what goes inside a studio. The actual studio is the room you use them in. And that room can have at least as much effect on the final quality of recordings as the equipment you use. The reason is acoustics.

Acoustics is basically about three things: reverberation, resonance, and isolation. Reverberation is fairly straightforward. Sound waves spread out in all directions from their source. When they hit something, like a wall, they're either absorbed or reflected. So if you put your ears, or their electronic equivalent, a microphone, at a particular position in the room, you'll hear the sound that's travelled directly from the source to your ears, plus all the reflections from walls, floor, ceiling, windows and furniture.

Sound takes time to travel through air, so the reflections arrive later them the direct sound. And a room creates multiple reflections as the sound 'bounces' to and fro between the room's reflectors. So the bigger the room, and the more reflective it is, the longer before all those reflections return, and the longer before they fade away. This is called a 'live' room, and the opposite is a 'dead' room.

To complicate matters further, different surfaces will absorb and reflect different frequencies. For example, curtains absorb treble, but have scant effect on bass. It's this difference between materials that creates what is called a 'bright' (trebly) or 'warm' (bassy) acoustic. Obviously, if you move the sound source or your ears, you'll change the acoustic result. And if you put the source and your ears next to one another, you'll hear more direct sound and less reverberation (and, with a 300 watt combo, you'll go deaf too).

Resonance. As sound waves fly around creating reverberation, they may also get amplified at certain frequencies only. These resonances only occur in the bass range, where they tend to 'colour' sounds by making some notes sound louder than they started out. Just which frequencies are affected is determined by the distance between the walls, and between the floor and ceiling. Just like reverberation, the resonances all contribute to the total 'sound field' at any particular point. The worst possible room is a cube, because all the resonances are at the same frequency and some very noticeable amplification goes on. For example, an 8 x 8 x 8 front room is very bad news, a 12 x 8 x 8 room is fairly bad, and 12 x 10 x 8 pretty good.

One more word about resonance. Buzz. (No, not that sort.) You play a certain note, and Aunt Agatha's picture buzzes. You play the same note louder, and it falls off the wall. That's the kind of resonance you don't want (unless you love the sound of breaking glass — hey, good name for a song there). So play through from your deepest notes to your highest and listen for any buzzes.

Just one more item, and then we can get down to applying all this theory. Isolation. There are lots of different types of isolation you may need: to keep the sounds of passing traffic from being picked up by your mikes, to keep the drum sounds from getting into the guitar mike, to stop cans' foldback from getting into microphones, to stop live sounds getting through to wherever you're monitoring, or, of course, to stop your 300 watt combo driving the neighbours insane at three in the morning.

OK, let's see how all this pans (ha, ha) out in practice. The ideal is obviously a room you can use permanently as a studio. Then you can do pretty much what you like to tailor its acoustics. But...

Today's commercial sounds need voices and instruments to be close-miked, with reverb added electronically. So you want a dead acoustic for recording. But when it comes to monitoring the result, to add EQ, effects (including reverb), and balance the mixdown, you do actually want a reasonably live acoustic. Why? Because, when you submit your demos, they'll be listened to in a room with living-room type acoustics. So that's what you've got to balance it to sound right in. If you balance in a dead room, you'll add far too much reverb, bass and treble, and the result will be a muddy, shrieky mess when played in an ordinary room. Nicht gut.

So we've got a conflict. Dead for recording; live for monitoring. One answer would be to deaden the 'studio', and use your living room for monitoring. But that can mean lots of running to and fro. Alternatively, if the room's big enough, you can create a live end and a dead end. But with a smaller room, anything below about 25 feet long, this won't be practical. Neither approach helps much if, like most people, your studio also has to double up for some other, totally trivial purpose, such as the family living room.

The answer is variable acoustics.

Which brings us to the practical matter of how you actually alter acoustics. In all my years (sorry, my calculator can't handle such long numbers), I've used or seen just about every cheapskate trick in the book.

The first studio I ever designed was for a university radio station. The room was a near cube, and boomed like mad. Also, having gone over-budget on the equipment, we'd got about £5 for acoustic treatment. £5? No problem.

Ingredients: one large tin of glue (£1.50), and a six pack of beer (£3). Installation instructions: hand six pack to local grocer/supermart in exchange for a pile of abandoned old egg trays, and get busy sticking them on the walls and ceiling. Because of their material and shape, egg trays quite effectively absorb sound and cut down resonances (also there's the entertainment value of watching them come unstuck and fall on people's heads at vital moments).

But egg trays are kids' stuff compared to one home studio I saw. I say studio, though the place actually looked more like a psychedelic padded cell. The guy had decided that mattresses would really deaden the acoustic, so he'd bought a whole pile of them dirt cheap (and pretty dirty) from a junk shop, then simply nailed them to the walls. Radical, but very, very effective. (Don't try nailing them to the ceiling though; a mattress on your bonce is not so funny, though one on your manager's trilby might be...)

More expensive, slightly less effective, but far less distressing to look at, are floor-length heavy curtains (of rugs) over the walls. A great advantage of curtains is that they can provide the variable acoustic I was talking about earlier. Close for dead acoustic, open for live. True, it means you've got to walk round changing curtain layouts fairly frequently, but if you're too smashed to manage that, you can always crawl round. (Canny shopper hint: since you'll need an awful lot of curtain, the best place to buy is a street market. Even though markets are already cheaper than shops, with the amount you'll need for a whole room, you should he able to haggle at least another third off the asking price.)



"I've actually known people deaden sound by carpeting their walls... trendy."


Carpets can also deaden acoustics, but note that, unlike curtains, thicker, more expensive carpets aren't really much more effective than cheapish ones. I've actually known people deaden sound by carpeting their walls (no kidding, there was a time when it was very trendy). But heavy curtains are nearly as effective, and they don't take the plaster off the walls when they fall down.

I haven't (yet) met anyone who's carpeted their ceiling (even worse than mattresses suffocation-risk-wise), but ceilings do play an important part in room acoustics. Look, or rather listen to it, like this. You've deadened the floor with carpet. You've curtained the walls (and presumably the windows). So now the ceiling is the only highly reflective surface left.

If you've got the ceiling height, you can't beat a sloping false ceiling covered with acoustic tiles (three degrees or more slope; low at speaker end, high at listening end). It cuts resonance and adds a feeling of depth to monitoring sounds. Also, if you're a DIYer, it needn't be all that expensive. However...

Provided, and I stress PROVIDED, you've already deadened the floor and walls, then the answer is called (techo-waffle warning) unidirectional or cardioid mikes pointed downwards. This way they'll pick up less of the ceiling reflections.

If your room's got a strong resonance (bass boom), then it's time to get DIYing. Buy some 8x4 sheets of hardboard (name must have been invented by marketing entity, since hardboard possibly softest wood known to man), then glue carpet to same. Position them in the middle of walls, leaning so they're angled slightly upwards. Result may look weird, but if you use enough to cover 40% of wall area, guaranteed effective.

And now it's time for isolation. If the problem is incoming sounds, then their entry point has to be identified. For windows, you need two things: acoustic double glazing, plus money. Acoustic double glazing can cost £200-£1000 depending on the size of window. The main differences between ordinary and acoustic DG is the space between panes (at least six inches for the latter), and the fitting of acoustic tiles covering the gap's sides, top and bottom. You can also have thicker than normal glass, which helps improve bass isolation.

Noise transmission through doors can be reduced by felting all edges (don't use draught excluder strips, they just don't work).

If bass noise is coming in via the floor, then you're in for mucho money. In principle you can use fibreglass or preferably Rockwool to deaden both floorboards and joists, but the reduction isn't going to solve any serious problem. Move to country mansion.

If you're getting deep bass rumbles from traffic, and you're trying to record vocals, or an instrument that hasn't got any deep bass, then you could filter out the rumble with tone controls/sweep equalisers. But this ties up an EQ control. Instead, try Tandy's PZM mike (£24.95, Cat No 33-1090A), actually Blutacked onto the instrument (but not onto the vocalist). The PZM's bass response depends on the size of panel it's mounted on. If you just use it without any panel, but held by a mike clamp, you'll filter out rumble without wasting an EQ control. Clever, huh? And cheap.

Isolation between instruments: get DIYing again. The standard answer is to make screens out of hardboard and carpet, mounted on bases to hold them upright. But don't expect miracles; the best you can hope for is a 15-20dB reduction in spill level, and even then only at mid and high frequencies. Uncle John's answer: make a large box out of plywood or chipboard, line it inside with carpet, then dump it over the amplifier and mike. Sounds daft, but this not only improves isolation, it also often improves tone quality.

Foldback spill, usually a problem with vocalists, can only be solved by using 'closed-back' cans. You can buy really nice Beyers for around £60, or cheapos from about £5. The main thing is to make sure they're comfortable.

And so we come to the biggest toughie: isolation to stop your wonderful music upsetting philistine neighbours. Letters to editor suggest this is probably your most common acoustic problem, so I'm really glad we've done away with that nasty old habit of killing the bearer of bad news. Because the news IS bad. All my tricks (except for egg trays) to deaden acoustics will help reduce noise transmission, but not enough to make a radical difference.

You can deal with the problem, and also all incoming acoustic noise, by creating a 'floating' studio. This is basically a room within a room, mounted on enormous springs. But at £10,000+, you'll also need an enormous overdraft.

More realistically, try that recipe above (sticking amps in absorbent boxes), and if that doesn't work then you'll have to change the way you work: everyone listens on cans, all instruments go by DI (yes, I know that means you'll lose the 'quality' of your 300 watt combo), plus the drummer has to be reprogrammed and re-equipped with a synth kit. I know the whole idea hurts, but truth is like that.

To end on a sweeter note, a few words about monitoring. You would be amazed at how much difference speaker positioning makes to sound quality. Good monitoring is essential for good-sounding demos. Try raising and lowering your speakers, moving them in and out from walls, and tilting them. Do all of this using good quality commercial music. Take your time; it really is worth it...


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Making Music - Copyright: Track Record Publishing Ltd, Nexus Media Ltd.

 

Making Music - Mar 1987

Feature by John Peel

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