Not just for studio control rooms, but also for any room where music plays through loudspeakers, a worthwhile goal is to create a reflection free zone at the listening position. The concept is very simple – to prevent early reflections (also called first reflections) from obscuring the stereo image and degrading clarity. This occurs when sound from the loudspeakers arrives at your ears through two different paths – one direct and the other delayed after reflecting off of walls, ceiling and floor. The reflections obscure fine detail and make it difficult to localize the source of the sound or musical instrument.
The general goal of a reflection free zone is to eliminate the early reflection paths by placing absorbing panels in key locations. It’s equally important to avoid early reflections off the ceiling, floor, and mixing desk if present.
When an echo that arrives within 20 milliseconds or less accompanies a direct sound, the ear is unable to distinguish the echo as a separate sound source. So instead of sounding like an echo or general room ambience, the sounds coming from different directions combine, which obscures clarity and confuses the stereo image. You can still tell when an instrument is panned all the way to the left or right, but the in-between positions are not as well defined. Put another way, listening to music in a reflection-free zone is similar to listening with headphones — musical instruments sound clearer and their placement in the stereo field is much better defined.
When the budget allows for dedicated studio construction, early reflections can be avoided by angling the sidewalls and sloping the ceiling upward. Given a large enough angle – at least 35 degrees — the reflections are directed behind the listening position without having to apply absorbing materials to the walls or ceiling. This lets you better control the overall ambience in the room because you don’t need additional absorption just to get rid of the reflections. But most people do not have the luxury of building new walls, so the only option is to apply absorption at key locations.
The easiest way to tell where to place absorption to avoid early reflections is with a mirror. While you sit in the listening position, have a friend place a mirror flat against the sidewalls and move it around. Any location in which you can see either loudspeaker in the mirror should be covered with absorption. It’s a good idea to treat a larger area of the wall than you identify with the mirror, so you’ll be free to move around a little without leaving the reflection-free zone. Once the sidewall locations are identified do the same on the ceiling. Although it’s more difficult to slide a mirror around on the ceiling, one way is to attach a hand mirror to a broom or garden rake with rubber bands.
Finally, it’s important to understand that the range of frequencies absorbed affects the quality of the reflection free zone. Some people use thin panels made of fiberglass or foam, or blankets, and believe that’s sufficient. But those materials absorb reflections at higher frequencies only. Broadband absorption kits such a TruTraps GENESIS systems by Auralex will give you control of the lower range of frequencies as well.
As ever, if you require some assistance in choosing the right sound absorption materials for your home studio, contact your Sweetwater Sales Engineer.