Potential new room, will this work well?

NP,

That room mode calculator will show you a graph of the "general" locations of where reinforcements will occur in the frequency response and how large they will be (relatively). You can always use that to see about any other room sizes you are considering in the future.

Also,

If you have no other choice, you can always do what I did... Have an acoustical engineering group like Rives Audio consult with you and design the room to at least limit the room response as much as possible. I would recommend that no matter what you end up doing. That way you can have your room designed with optimal sound treatment.

Jkalman

I've read his posts before...he is not a total newbee. His question was fairly general...so was my answer. I left the exact placement of the "new" rear wall for him. The other walls, and the ceiling are already fixed in place...yes?

If he does some of your reading, I'm sure he can come up with something, other than the wrong place to build the wall? (40' is a lot to work with)

BTW, I did build my audio room, with a little help from my son...and a few friends that were unlucky enough to stop by at the wrong time....great acoustics, if I do say so myself.

I've looked at your room (very nice!)....I can see why you have a few problems though, and they are not the rear wall....of course you knew that.

Dave

Dave,

I have a group of modes overlapping in the 60s and clustering in the low 70s frequency-wise. I know this because I have tried a couple of different speakers in similar positions in the room. Building a bass trap for those frequencies would require a bass trap way too big to be convenient (or sane).

I'm sort of stuck EQing unless I decide to abandon the Home Theater part of the room and get more liberal with speaker placement. I've been looking at some of the analog pro equipment used by Steve Hoffman in his system as potential solutions I could use. I do need something that can both add gain and take gain away from certain frequencies. Luckily, the pro equipment tends to have options that fall right on my problem areas. Rain has some a nice looking options as well, though I might just spend $300 on a Behringer to play around with first (I do like some warmth in the bass region). Also, it would allow me to change things on the fly, for individual recordings.

He will have a very sweet room if he makes it 39' or 31' on that longest room dimension (39' would be best to maintain room volume). I'm jealous of those 11' ceilings... I had to build all the way up to the joists to get 9'. I had steel beams to deal with, and steal support pipes, and a large iron septic output from the house that I had to enclose in a soffit closet. I can't complain though, because my wife let me have the room to do whatever I want to it.

Dave,

Here is one I'm heavily considering as well:

http://www.rane.com/peq55.html

It is around $800 and gives a very nice spread, as well as balanced I/O. I could even double dip and get two of them so I can PEQ more areas, if I want to later on.