Square room with vaulted ceilings

Mapman,
Thanks for the response. This room is in a house that I'm looking at, so unfortunately I can not give it a try! I'm glad that you're getting good results in your square room, though. That's promising.
Any other thoughts?

My "audio room" has a cathedral ceiling (same thing as vaulted?) 8'-11' high. I think it sounds fine, though I do not crank the volume to extremes. But I have been told by an expert that the ceiling can act as a horn and should be treated at the seam with broadband absorption panels. I haven't tried this as I prefer sleeping in our bed rather than one of the stalls in our barn.

Square rooms are tough. Vaulted ceilings can be good--but not always. I would put your equipment in the room and take some basic frequency measurements with a test CD (we sell one) and a Radio shack SPL meter. See what the response is below 100 Hz. If you have 10 to 12 db peaks which is likely with those dimensions it's unlikely you will smooth things out without the use of a parametric eq. If your peaks are more modest then you may be able to tame them enough with appropriate trapping. If so, then you could wind up with a very comfortable listening area.

Obviously, you would need more than just bass traps--but that's going to be the biggest hurdle. If you get over that one the rest is almost certainly doable--unless you have a wall of glass or something else you haven't mentioned that could create other problems.