Studio Tech Tip - Taming the wild bedroom
By Dennis Kambury

If you're like most of us, your studio is an extra bedroom or basement. Usually small and boxy, these rooms are designed for habitation, not musical creation. Their dimensions cause hot spots, dead zones, and flutter echo, making live recording a challenge. However, there are ways to tame your music room that will make it far more effective.

A brief nod to acoustics

Everybody knows that rooms can make or break a sound. Look no further than the bathroom singer - a legend in their own mind, rivaling the greats, as long as they remain in the confines of the bathroom. Why? The dimensions and hard surfaces of the typical water closet allow standing waves, echo, and reverberation to flourish, giving the singer's voice a fullness and depth that it doesn't normally enjoy.

Think of a room like the harmonic series on a guitar string. Starting at the 12th fret - the octave - and working towards the bridge, the harmonics become more closely spaced. The intervals move from octave to fifth, fourth, third, and so on until at last, they're only microtones apart. Rooms exhibit a similar response pattern, with air taking the part of the string, and opposing walls acting much like the nut and bridge. The length of the room determines the fundamental frequency, and the first harmonic is the lowest-frequency standing wave that will develop. For the technically minded reader, the formula for this frequency is f1=565/L, with L being the length of the room in feet. Each successive standing wave can be found by multiplying f1 times 2, 3, 4, and so on.

At this point, the astute reader will note that unlike a guitar string, rooms have more than two walls, as well as a floor/ceiling relationship to consider - resulting in very complex interactions that require some serious engineering knowledge if you want to gain control of the situation. Or do you?

Reflections on a sheet of drywall

Why are bathrooms bright and reverberant, while bedrooms are usually warm and quiet? By the simple addition of soft beds with big blankets, curtains, wall-to-wall carpeting, dressers, and other furniture! Reflections are broken up, sound is absorbed, and standing waves are greatly diminished. To tame your music room, take the same approach - break up and absorb the sound waves, and you'll be well on your way to a decent sounding space - all without an engineering degree!

Breaking up

One of the tried and true ways to reduce standing waves is diffusion. Resorting to analogies again, think of your walls as parallel mirrors, and sound waves as the seemingly endless reflection of light between them. By substituting one of the mirrors with, say, a disco ball, the recursion is effectively destroyed, as light is scattered in every direction. So it is with sound. Break up the flat surface of one wall with a bookshelf, and sound waves scatter, leaving flutter echo and higher frequency standing waves behind.* This alone will go a long way towards improving your room. A more elegant solution can be found with products such as the Auralex T'Fusor that use careful design to promote broadband diffusion.

Suck it up

The other part of taming your room is absorption. For this, hanging blankets on the walls, using upholstered furniture, laying carpet, and hanging curtains will absorb flutter echoes and standing waves, lowering reverberation and lending a more refined sound to your room. It's not necessary to layer every surface with absorbers, and in fact, studies have shown that alternating absorbent and reflective areas is even more effective.

Where to put it

The hard truth is that no matter how much you decorate your walls with absorbers and diffusors, the art of small-room acoustic treatment is making the best of a sub-optimal situation. I've adopted a homemade blend of treatments that essentially keep my listening area relatively reflection-free, but leave enough hard surfaces to keep the room from sounding dead. My mix position is surrounded on three sides with Auralex LENRDs and 2" Studiofoam panels. One sidewall has patches of Studiofoam plus an overstuffed couch, and the other is curtained - in part to alter the acoustics, and in part to let the light in! For the back wall, I use shelving and instruments to break up the sound. LENRD bass traps fill all corners, and the floor is a firm carpet over a thick carpet pad, all on concrete. Bottom line - it sounds great, especially for vocals and acoustic guitar. You can view the room at http://www.idora.com.

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*Low frequencies are much harder to tame in the typical spare-room scenario, and as such are beyond the scope of this article.

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