Quick Home Studio Acoustics Primer

Many musicians and home studio enthusiasts place top priority on expensive plugins, computers, monitors, and other gear. Those are great things, but the well-initiated know that when it comes to making a home studio great, acoustics is where you can get the most bang for your buck.

Whether you’re recording and want to capture a better sound or mixing and want your mixes to sound great elsewhere, properly treating the room you work in is the best way to supercharge your results.

You may think acoustic treatment is the sole purview of expensive, professional facilities, but that’s not the case. In fact, it’s relatively easy to make a significant improvement to your acoustic environment, even on a budget – if you understand a few basic concepts.

We’ll go over some of those here to get you started improving the sound of your home studio.

Why Treat?

If you’ve ever walked into an empty bedroom, you know why acoustic treatment is so important. In a hard cube with six parallel surfaces, sound reflects and interact with each other and the direct sound, causing peaks, nulls, comb filtering, and all kinds of undesirable acoustic phenomenon.

If you’re recoding or mixing music, this obviously poses a problem. Since its unlikely you can rebuild the room a different shape, you’ll need to treat it to tame and control its acoustic characteristics.

Soundproofing?

Before we go too far, we should distinguish acoustic treatment from “soundproofing”. Soundproofing really means isolation – aka making sure your sound doesn’t leak into other rooms or bother neighbors (or vice-versa). Isolating a room is a very different job than treating it, and sometimes the two tasks are at odds. So, we’ll leave off isolation for another time, and just talk about treatment.

Absorption and Diffusion

There are two basic solutions to the problem of reflections interfering with each other and causing ugliness: absorption and diffusion.

Diffusion spreads reflections in an even manner, so interactions aren’t as extreme. In a big space, diffusion is an excellent way to create an even, beautiful sound which is not too “dead”. Many types of diffusors are used in big recording or concert spaces to create live, even sounding spaces.

Unfortunately, diffusion requires a lot of space to work and most home studios are just too small. So strategic absorption is most likely your best bet.

If it’s not obvious, absorption simply means absorbing all or most of a sound wave when it gets to a surface, rather than letting it bounce off and cause problems in the room. So, we’ll look at absorption from here forward.

Lows and Highs

While low and high frequency waves are technically the same animal, they need to be treated differently, mainly because of their size difference (low frequency waves occur literally over a longer distance).

For treatment purposes, think of low frequencies as anything below about 400 Hz and especially below 200 Hz. That’s the bass and low-mid bass area. For reference, middle C is 262 Hz.

Low frequencies are usually more problematic because you can’t hear them interacting just by clapping or yelling in a room. These frequencies build up or cancel each other out in different spots in the room, causing listeners to hear the bass inaccurately during mixing, or mics to pick up less than ideal low-end information during recording.

Low frequency interaction might cause a room to sound boomy, a bass drum to sound dull, or a mix to sound thin, to name just a few examples.

High frequency problems can be heard as ringing, resonating, boxiness, echo, phasing, or other audible phenomenon. In recording, these problems can cause instrument to sound flat or extra boomy, make vocals sound ugly and lifeless, or even give a reverberant quality that you don’t want.

In mixing, uneven high frequency reflections may skew the stereo field, or create a wash of sound which makes it hard to hear the difference between left and right, how reverbs and delays sound, or even just how details interact in the mix.

Simple Solutions

As mentioned above, the quickest and often the best solution to these problems is simply to absorb reflections.

High Frequencies

At high frequencies, this is simple. Think of a high frequency sound wave like a ray of light. It bounces off a wall at the same angle it approaches. In many cases one can easily see where you might need high frequency absorption, but here are some quick tips:

1. Floor or ceiling – Floor coverings can make an incredible difference in a noisy room very quickly, but professionals often leave floors uncovered and treat the ceiling instead.
2. Reflection free zone – in a mixing room, it pays to absorb high frequencies in the area surrounding the mix position. Directly to your left, right, and above you are the areas which cause the most problems. You can also treat the wall behind your speakers, but not every pro does this, because speakers don’t necessarily fire backwards. Many pros leave wall behind them live, or if the room is big enough, they use diffusion.
3. Even out a recording space – In a recording space, there’s not necessarily one area you’d like to sound good. You don’t necessarily have to treat every surface – in fact, that may create an undesirable deadness. Instead, evenly space acoustic panels around the room to tame reflections and even the response.

Low Frequencies

Because of their length (often longer than the room), low frequencies act less directional than high frequencies. Still, they do reflect and interfere with each other, and the solution is almost always to absorb them.

In theory, material that absorbs high frequency waves would also absorb low frequency waves – if it were thick enough. The problem is, in order to effectively absorb lower frequencies, panels would need to be very thick – think eight or more inches. Since most people don’t want to give up a foot of space around their room, low frequencies are usually dealt with differently. Consider these few principles to treat low frequencies:

• Corner traps – Bass tends to build up in corners of the room, so this is a great place to absorb. Corner traps of various types are available for this purpose, and ideally should be used in every corner of a room.
• Panel traps – A panel trap is a low frequency absorber which uses any of a number of resonating membrane techniques to absorb low frequencies while reflecting highs. This kind of absorber is very handy for taming the low end of a room without making it to dead sounding at high frequencies.
• Absorb more – In most rooms, you can’t absorb too much of the low frequencies. So, look for areas beyond just the four vertical corners where you might use various kinds of low frequency absorbers. You can absorb too much high frequency information, depending on your goals and taste, but low frequencies should be generously treated until the room responds the way you want.

We hope this primer has helped you get a grasp of the basics behind tuning up your studio. Let us know in the comments your favorite techniques and acoustic products.

Also in Audio Info & Education