We made the mistake of building out a place for ourselves a few years ago. Talk about stupid... Anyway during that time I read some books and did a lot of research. punchline:
One of the books said the BBC (I have no idea why it quoted them) did some studies and found that rooms smaller than (I dont remember) wont work at all. Also no matter what size the room you will get some room modes so you have to use the formula(Dont remember how to do that either) to come up with something that makes sense. The point is do a search for "BBC" "room size" or "modes formula sound" etc etc or whatever in google and Im sure you will find some great resources...... Or wait a few hours and let the posts fall in. There are some super people on here that know everything. The book is actually sitting on my bookshelf but I dont want to grab it for 2 reasons.
1. Im lazy and I am sure you can google it.
2. I dont want to try to talk like I know something about this stuff because I dont and like I said the dude that wrote the book or his teacher probably log on here.
Ya know what I wanna say something else. There is SO much stuff that goes into a room... Think if you are really gonna get anything outta spending time and energy on it. Yes every little bit helps but at the same time you gotta ask is it really worth it. We spent 3 months and a lot of money building out a 2200 sq ft place. Double walls, Live room, control room, pre production room, insulation, hours and hours of research. And at the end it looked kinda good... But... It didnt sound MUCH better than if we just took over office space except for the double walls. That was good but you could still here the cars on the street that were 200 + feet away with the U87. I will say I had a great time and learned a lot so in that sense I would do it again. But with what was spent we could have had someone who knew what they were doing build something real. The place had flutter like you cant believe. And 3 days after the control room window went up the velvet we put in between the glass came down. The guys had so much trouble putting it in it stayed like that for a year.
If you do nothing else... hire a pro to design the shell of the room. The shell IS your bass response. You can bungle around like an idiot until you stumble on other treatments that serve your purposes... but if you don't have a good shell you might as well call it a day [or save the money and do nothing!! as you'll be even more fukked with something you think is "built" than something you know isn't "built"].
The standard modal approach for designing a room with good acoustics is to create as many different resonances as possible, and to spread them as evenly as possible across the frequency spectrum, as discussed in the Handbook for Sound Engineers, Chapter 3. There is even a complicated "Bonello Criterion" to evaluate the spread. The lowest resonance is determined by the largest dimension of the room. (Technically there is also a resonance at zero Hz for all rooms, but this is generally not considered a true resonance). In general, the lower the better for the first resonant frequency, because this region is where the frequency response is most variable. Bigger rooms also reduce the spacing between resonances. The limiting factor here is usually cost. For a 19-foot long room the first resonance is about 30 Hz. Every harmonic of this frequency (60, 90, 120, etc.) is also a resonance. The width and height of the room each give rise to another series of resonances. These are the primary "axial" resonances, involving reflections from two opposing surfaces. Additional resonances are created by reflections that ricochet off four different surfaces. These "tangential" resonances are generally weaker, because energy is lost at each reflection. Finally there are "oblique" resonances which ricochet off all six surfaces. Each resonance gives rise to a "mode" with a characteristic spatial pressure variation. The mathematical description of a mode is given in the physics section, and some graphical examples are illustrated below. To spread these resonances as uniformly as possible, various ratios between the room height, width, and length have been proposed. Three such sets from the Handbook for Sound Engineers are shown in the table below.
See the link for the table....
According to the modal design theory, the worst possible room shape is a cube. The next worst is a room where all dimensions are multiples of the height. A pretty horrible example is a room 8-ft high, 16-ft wide, and 16 ft long. The resonances for an optimum room (design #3, width =1.60 x height and length = 2.33 x height) and for the latter horrible example illustrate the difference in the resonances [10.7 kb]. The two rooms have the same total volume. The horizontal frequency scale varies from 0 to 200 Hz. Each vertical line represents a resonance. There are three tiers of lines; the highest tier represents axial modes, the middle tier tangential, and the lower tier oblique. The resonances for the horrible room are less dense, because many occur at exactly the same frequency, and there is a fairly large gap between the second and third resonances, at about 60 Hz. The blue, green, and red lines represent resonances related to the room length, width, and height, respectively.
The part that keeps the sound in the room. The 'isolation' that keeps it so the neighbors don't shoot you, the wife doesn't divorce you [believe me, you're the only person who wants to hear that fukking song 9000 times in a row].
You can do whatever you want with the interior treatments, it's the "shell" dimension that will determine the bass response. The bass response will determine whether or not you have a prayer in hell of getting a mix out of the room that will even moderately translate to the outside world.