Listening Room Dimensions... I'm building one and need your help

There are obviously many, many issues involved in constructing a good-sounding room, and room dimensions is only one. As long as you don’t design a room that’s nearly square then there are probably other factors to address that may be even more consequential to your ultimate result. The best advice I can give is to educate yourself on at least the basics and principles of constructing a good dedicated listening room. Knowing just the basics will put you in a MUCH better position to make critical decisions even if you end up working with an expert. I went through several books, etc. in trying to get a handle on this myself, and BY FAR the best thing I did was read Premium Home Theater: Design and Construction by Earl Geddes (no longer in print, but you can download it at gedlee.com). Don’t let the title fool you — this book is as relevant to building an audio-only room as it is to HT as the design principles are largely the same. More than any other source I found, this book explains both the theory and practice of designing and constructing a good-sounding room in a very approachable way so even a layman like myself can easily understand and comprehend them. And it also gives specific recommendations on the actual products to buy to complete a project, which I found most helpful. Before I read the book I didn’t even know what a resilient channel was, but now I’m confident I could instruct any contractor how to build a very good-sounding room (and I know nothing about construction). Even if I wasn’t building a listening room I’d find Earl’s book to be an interesting read. After all, I think most of us would agree that the room is one of — if not the — most influential components in our sound systems, so why not get a little smarter about it? Hope this helps, and best of luck with your project.

I agree with @bdp24  about the golden ratio though I don't think Cardas was its inventor. It goes back to BC time and is found a lot in nature. I'm going from memory now so ...You can google it

True @artemus_5, the ratio is not of Cardas' invention, merely his "re-discovery". He uses it in the construction of his cables too, the relative sizes of the various gauge strands of wire he combines.

@bdp24 

He uses it in the construction of his cables

I did not know that. I don't have any Cardas cables. Maybe I should try one?

My recommendation - don't do it. I simply would not try to make a premium two channel room that also would be for band rehearsal. I would find another place to rehearse. You may not have that option, but if you do, I advise you don't mash sonic attributes of the two together. 

If you go for the band rehearsal sized space, you will be building a cavern, not a room. The entire experience, including what gear you will need to run to make such a space seem appropriate will differ. Are you ready to pony up perhaps triple the money you have invested in audio to get the results appropriate for the space? 

It seems like you have lots of room to work with; why not build two rooms appropriate for their purpose? You can use a common wall, but use different construction techniques for each on other walls. You can send me the consulting fee if you do so. ;)