I think this might help:
<In recording room acoustics the most important rule to remember is - avoid “like dimensions”. In other words, a "square" room will make a poor studio.
Another important rule is; avoid large parallel surfaces.
Both of these conditions produce "standing waves" and "flutter echos." In cube shaped rooms with parallel surfaces, sound waves, at critical frequencies, can be reflected back and forth across the room with surprising intensity. This effect can occur between walls or between the floor and the ceiling. The condition appears as a machine gun, "rat-tat-tat" sound when you firmly clap your hands together oncewhile standing in the center of the room. This condition must be avoided in studio design and construction.
Ideal dimensions for recording rooms can be calculated by using the following ratios:
#1 Small rooms > Height=1, length=1.6, width=1.25.
In other words, to build a small music studio, the ceiling should be 10 feet, the width 12 1/2 feet and the length 16 feet. Using these dimensions, with non-parallel walls, floor and ceiling, and with a good amount of full range acoustical treatment, you will have a fine small studio.
When choosing dimensions for a studio or evaluating an existing design, it is imperative to have major dimensions that are not related to each other. Even with non-parallel surfaces this is extremely important.
Related dimensions produce resonances or peaks in a room's response. Related dimensions are divisable by each other, or a root number. In other words, a room with a ten foot ceiling height that is 20 feet wide and 30 feet long will, predictably have standing waves, flutter echos and will not be suitable for a recording studio. Related dimensions produce a hang-over effect at critical frequencies.
Ideally, in studio design, the most important goals to achieve are, a good distribution of natural resonance in the room, coupled with absorbtion and diffusion of reverberation over a wide range of frequencies. The real key to achieving a great sound from a studio is acoustical design. Fine studios are rarely an accident, they are carefully planned and thought out.
The same factors apply to control room acoustical design with one exception. The control room should be approximately 25% more "dead" than the studio. This must be in the form of wide range acoustical absorption. By making the control room more dead than the studio it is far easier to hear the sound of the studio itself by removing the coloring effect that a too reverberant control room would add to the sound of the mix.
Acoustically a control room cannot be made to be absolutely without peaks and valleys in its response. Even with the finest monitor speakers and power amplifiers there may still exist strong peaks that may be quite noticeable. To compensate for this condition measurements must be made with the control room monitor speakers and a calibrated microphone system. The peaks and valleys are noted on a graph covering the usable range of the control room monitor system.
The dimensions I have suggested may be varied somewhat to fit existing spaces. Adhering as closely as possible, however, will avoid tremendous problems when laying out over-all studio sizes and shapes, or in fact, any room in which music is to be performed.
Sound travels through materials of different density at different speeds. Using several different materials in wall construction will help to isolate a wide range of frequencies.
It is not necessary to use acoustical doors in studio installation. A solid core exterior door, properly hung, gasketed and sealed all the way around makes a fine acoustical door.
High frequency absorption is usually vastly over-done in uninformed studio design. The inevitable result is a muddy, lifeless sound that sounds tlike an "audio closet." Removing the high frequency resonance of a room by over-use of acoustical tile and/or sprayed on rock, wool, or asbestos, or any other method, spoils the harmonic balance of any music performed in the room by reducing the intensity of harmonic over-tones, thereby destroying their relationship to the fundamental tones.
This effect is minimized somewhat by close-miking techniques, but the false relationship andharmonic imbalance that is the result of high end loss is clearly evident.
There you are.....