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One possibility, depending on what else is on the same floor, would be to make one of the walls "flimsy" so that most of the bass passed right through. To some extent, the bass response would then be a function of the size of the overall floor rather than just your room.

A single layer of drywall always seems to be about "half a solution" for bass response -- not heavy enough to fully reflect the bass but heavy enough to make a big difference. My dim understanding is that as the wall gets more solid then the room dimensions to that wall become more of a factor, with drywall about half way there. Glass, on the other hand, seems to be light enough that the bass largely goes through it.

Do a search for "modecalc download" and you can get a handy little utility from Ethan Winer which translates your room dimensions into frequencies for you so you can get a rough idea where and how bad the frequency bumps will be.

BTW, I would not drywall out the corners -- better to do the "superchunk" thing if it turns out to be required.

BTW, I would not drywall out the corners -- better to do the "superchunk" thing if it turns out to be required

I am not using drywall at all. I am actually installing 1/2" luan plywood on the walls, which should be more solid than drywall. Then at the first reflection points I am installing 18" wide carpet squares from floor to ceiling over the plywood. Then in the corners the same treatment. 45* plywood corners with carpet squares from floor to ceiling. The carpet squares are approximately 3/8" thick with a heavy rubber backing and, by the way, free, as is the 1/2" plywood.

The plywood has a nice grain to it, and I will be able to stain or paint it for a nice look.

I went to the modecalc - WOW - I changed my dimensions of the room so it is not a perfect square, the length is 10" longer than the width, plus I will have 2' bulkheads running the length of the room on either side, so my ceiling height will vary - 8' in the center (9'10"x14'8") and 7.5' at the bulkheads. As far as I could tell, when I put the dimensions in, I only had two areas that overlapped colors. Not sure what I was looking at, but according to what I read that seems to be good? Again, thanks for all the help.

I'm not sure I necessarily agree that the plywood will be "more solid" than drywall. More rigid, perhaps. Denser? More reflective? More absorbent? Don't know. Certainly different relative to acoustic properties.

Listen to bridgman. He's an effing genius, but we try not to admit it too often. And he's far too modest.

My understanding is that the only benefit of manufacturing a room "out of square" is to tame the room nodes; it will not give you low frequency absorbtion like bass traps would. And it could give you some really wonky reflections at other frequencies.

Not all "non-hard-surface" treatments are created equal. I think your scenario sounds GREAT, but fiberglass panels and foam panels are certainly going to be different than carpet acoustically.

I'm guessing the plywood will be less dense/more absorbent than drywall- but I don't know either. I do know to agree with Tom, and with Bridgman- both offer top notch advice.

I agree that the carpet will be different acousticaly- probably will absorb highs, but not as effective as panels for the midrange.

Again thanks, you guys were posting while I was editing my post above. Not to get caught up in the specific material, just so I can begin to understand. 1) A perfectly square room is bad, but a perfect cube is worse. 2) It is acoustically beneficial to have some sort of sound absorbing material at the first reflection points. 3) It is acoustically beneficial to have some sort of sound absorbing material at the corners of the room. (or any corner for that matter) 4) It is also acoustically beneficial to sound reflective materials throughout the room. 5) There are mind boggling logorhythmms and calculations that make this crystal clear to some, and more confusing to others.

I sometimes wish I didn't have the drive to not only do things, but understand why. Then I could hire someone to do all this and sit back and enjoy it.

You know, that seems right to me.

But, I'm clearly in the "confused" camp. Fortunately, I stopped caring "why" quite a while ago. Around our house, the DIY home improvement crew is known as Team Close-Enough.

You just asked almost all the hard questions in room acoustics, without even pausing for breath

1) A perfectly square room is bad, but a perfect cube is worse.

Yes. Having one dimension be a multiple of another is almost as bad. This is only a problem in the lower frequencies, where the room itself acts as a resonator and emphasizes certain frequencies over others. The result is a boomy sound at the emphasized frequencies and "weak bass" at other frequencies. Bass traps (see 3) can lessen this effect, as can (sometimes) the use of an equalizer to reduce the peaks.

2) It is acoustically beneficial to have some sort of sound absorbing material at the first reflection points.

Yes. Here you are trying to ensure that the sound from the speakers reaches your ears without being immediately confused by "close" reflections. If there is enough delay between a sound and the echo your brain seems to figure it out when determining where a sound is coming from, but reflections which are very close in time to the original sound muck up your perception of "imaging", "soundscape", that kind of stuff. You are mostly worried about mid and high frequencies, so a couple of inches of foam or rigid fiberglass is just fine. Note that carpet tiles will probably absorb the high frequencies but are probably too thin to absorb much in the midrange frequencies.

3) It is acoustically beneficial to have some sort of sound absorbing material at the corners of the room. (or any corner for that matter)

Here we are talking about bass traps -- absorbing the lower frequencies. You need big thick absorbing material to absorb bass, so bass treatments tends to be big and, accordingly, expensive. Bass traps can go anywhere but are more effective in corners -- people put them in corners so they don't need as many of the big ugly things

4) It is also acoustically beneficial to sound reflective materials throughout the room.

Yes. The trick is to get the right mix of reflection, diffusion (bouncing in different directions) and absorbtion. When it comes time to do my room "right" I'm gonna call Rives and have them tell me what to do, since that stuff is way above my pay grade. In the meantime, just try to have a nice mix of surfaces and "stuff" in the room and don't worry too much.

Again, note that if you ONLY use carpet tiles for sound absorbing you will get a slightly wierd sounding room, where the high frequencies are absorbed but the midrange frequencies are still bouncing around the room like one of those old "superballs".

5) There are mind boggling logorhythmms and calculations that make this crystal clear to some, and more confusing to others.

Partially right. To the best of my knowledge this is not crystal clear to anyone. Even the best acoustical consultants only claim that the most basic room shapes and materials are crystal clear. They have been doing this for 25 years and still get stumped every so often.

If you read enough and do some experimenting you can go from stumbling around in the dark to stumbling around with very dim light... but that dim light makes a huge difference