My dad is starting the plans for a theater room. He is planning on building the room from in basement so he has some flexibilty as far as room size. The room that he came up with is 15'6" by 14'6" with a 3' extended by cutout centered on the 15'6" wall. The extended by cutout is 9' wide and 4'8" back. #1 My question is how bad will this room be for acoustics? He wants to have a 5.1 setup and a projection tv on the wall opposite the extended bay cutout. Initially, ignoring the bay cutout the room dimensions are nearly square. #2 How far off of square must a room be to avoid acoustical problems? (1'?, 2'?, 3'? or what) #3 Is this room considered a nearly square room with the bay cutout causing maybe even more acoustical problems, or can this be though of as almost a rectangular room?

Any thoughts or suggestions about this as a possibility for a theater room would be greatly appreciated. I remember someone who had a room almost like this and posted a question a couple months ago. It would be great if someone has a room like this and can comment on the acoustics of this room vs a regular rectangular room.

- Nick

This is very general but there are many variables. I have 5.1 in a basically square room. My biggest complaint is with LFE. My seating position is about 2/3rds of the way back but there is a noticeable weakness in deep bass effects from the sub woofer there. If I stand in other positions in the room, like the back corners, I get very strong bass. If I compensate in the listening position by turning up the gain, it becomes too much and too boomy in the corners.

Much of this could be helped a bit by adding changes to the room to help control the bass standing waves, reflections and all the stuff others can speak more technically about.

However, I am still happy overall. Even in my square room, visitors are amazed with the sound quality. Yes, it could be better, but only your more knowledgeable friends will know that. If your dad is a sound perfectionist and a redesign is possible, the square should be avoided. If he is an average joe, like I was before spending too much time in these forums, it might not be worth sacrificing other parts of his design plan if they are important to him.

I think this link will answer your question on optimal room sizes if you need to go there.
Optimal Room Ratios

Wow! I never sat down and calculate it, but the dimensions of my room is +/- 1 feet from room design #3. No wonder why I never had problems with my sub anywhere I tried it. Now I don't want to move ever!

I agree with Murph, check out those optimal room ratios for the best possible sound in your room.

If I had a big basement and could determine the size of the room, I would definitely build it to one of those ratios.

Wow here too! I didn't even consider this when I built my dedicated room, but I am also within a foot on the lengh (closer to 1/2 a foot) on #3. I also have no issues with the EP500's performance anywhere in the room. I never want to move either, I don't even want to leave the room sometimes!

Boy these sound engineers really know what they are talking about.

Paul

Those half-foot differences are significant. Notice how they specify ratios down to the hundredths place (e.g. 2.33, 1.54).

Interesting thred.

What happens when you extend one of the dimensions?
my room is W 1.44 and L 3.56 The room is 13 X 32 X 9 I'm guessing this is a bad thing.

Ahhh! You guys are jerks for bringing this up again! For the umpteenth time I measured my room (never write the measurements down for some reason) except this time I knocked my center off the shelf. All I could think as it plummeted to the ground was "If I try to grab it I'll lose my place and have to measure again." Imagine my horror when I saw an alarming number of black shards spread around the speaker. It was fortunate that a few recently purchased DVDs didn't fit in the shelf unit and heroically sacrificed their cases to soften the blow. My heart is still pounding.
Their selflessness shall be remembered.

We should all say a small prayer for Dormat's DVD cases, and maybe a few seconds of silence.

I am curious, if the room dim's are so critical, why is there no mention of height? I live in a 3d world. Axiom always talkes about volume or a room when recommending speakers. I would think the height of a room is just as important as the other 2 dims.

Paul

I thank you for your thoughts on this dark day.

Actually height is part of the formula. All the ratios are multiplied by height for room acoustics.

It would be standard 8' ceilings.

- Nick

I think that you are misunderstanding what I am talking about, maybe I didn't explain it well. There is only one room design. The room is 15'6" by 14'6" with a 3' extended bay cutout centered on the 15'6' wall. The bay cutout measures 9' by 4'8"(the 9' dimension is on the 15'6" wall). I want to know how bad this room design would be for acoustics.

- Nick

Nick, the basic idea is that the three room dimensions shouldn't be equal to each other or even multiples of each other. So, here 8x16x16 wouldn't be good from that standpoint. Your question about how far off does it have to be(1', 2', etc.)so that the room modes don't pile up near the same frequencies can't be answered with any certainty; just farther is better.