Room Acoustics!


The critical thing, for me, is to have a good sounding room that enhances what I am doing--recording instruments, vocals and listening critically while mixing and editing. Lets not forget, listening for pleasure too. Your audio pleasure factor is a good guide. A bad room really grates on my nerves in a short period of time. My ears get tired and I get a headache. Its like eyestrain for the ears. Anyone that has ever painted the walls in an empty room knows what an extremely annoying room sounds like. As you start moving furniture back into the room it starts sounding better. For a music studio, you want to do this in a more exacting way, to make the room actually sound pleasant and friendly to the ear.

 All rooms are boxes. It is good to think of them from "outside the box" to get some control over what is happening to sound. Generally, a small room will have more problems than a large open area as sound reflections will be magnified at the frequencies the box. Small rooms need more treatment as sound will bounce around the room, off the walls and ceiling many more times than a larger room. Also a square room is more problematic than a rectangular room, as having the walls the same distance apart can create strong "standing waves". You may have heard that in your room where a particular bass frequency rattles the walls but others do not. If you haven't, pull out a bass and play the scale and you'll find it.

There are two basic types of acoustic treatment - absorbers and diffusers. There are also two types of absorbers. One type controls midrange and high frequency reflections; the other, a bass trap, is mainly for low frequencies. All three types of treatment are usually required before a room is suitable for making mixing decisions and for serious listening.

Many studio owners and audiophiles install acoustic foam all over their walls, mistakenly believing that is sufficient. After all, if you clap your hands in a room treated with foam (or fiberglass, blankets, or egg crates), you won't hear any reverb or echoes. But thin treatments do nothing to control low frequency reverb or reflections, and hand claps won't reveal that. Basement studios and living rooms having walls made of brick or concrete are especially prone to this problem - the more rigid the walls, the more reflective they are at low frequencies. Indeed, simply building a new sheet rock wall a few inches inside an outer cement wall helps to reduce reflections at the lowest frequencies because a sheet rock wall that flexes also absorbs a little.

You may ask why you need acoustic treatment at all, since few people listening to your music will be in a room that is acoustically treated. The reason is simple: All rooms sound differently, both in their amount of liveness and their frequency response. If you create a mix that sounds good in your room, which has its own particular frequency response, it is likely to sound very different in other rooms. For example, if your room has a severe lack of deep bass, your mixes will probably contain too much bass as you incorrectly compensate based on what you are hearing. And if someone else plays your music in a room that has too much deep bass, the error will be exaggerated, and they will hear way too much deep bass. Therefore, the only practical solution is to make your room as accurate as possible so any variation others experience is due solely to the response of their room.

Without question, the most effective absorber for midrange and high frequencies is rigid fiberglass. Owens-Corning 703 and 705, or equivalents from other manufacturers, are the standard absorbing materials used by professional studio designers. Besides being extremely absorbent they are also fireproof and, when applied to a wall, can even retard the spread of heat. Rigid fiberglass is available in panels 2 by 4 feet and in thicknesses ranging from 1 to 4 inches. Larger sizes are available, but 2 by 4 is more convenient for most studio applications, and can be shipped more economically. As with all absorbent materials, the thicker it is, the lower in frequency it will absorb to. That is, 703 fiberglass one inch thick absorbs reasonably well down to 500 Hz. When two inches thick, the same material is equally absorbent down to 250 Hz.

There are a number of ways to create a bass trap. The simplest and least expensive is to install a large amount of thick rigid fiberglass, spacing it well away from the wall or ceiling. As noted earlier, 705-FRK that is four inches thick and spaced 16 inches away from the wall can be quite effective to frequencies below 125 Hz. But many rooms have severe problems far below 125 Hz and losing twenty inches all around the room for thick fiberglass and a large air space is unacceptable to most studio owners and audiophiles. Fortunately, more efficient bass trap designs are available that are much smaller. However, studios on a tight budget can apply rigid fiberglass in the room corners as shown in Figure 3a and lose only the small amount of space in the corners. Since bass builds up the most in the corners of a room, this is an ideal location for any bass trap.

Making your room acoustically right can be costly and still it may not give you the results you are looking for.  Other solutions could be to make a small vocal booth, enclose your mic in a small box that has been treated, I have seen large quilts and blankets hung that provided a decent sound.  At the end of the day you are better off with a dead, dry room than with a lively one because you can always add reverb as needed.