There are several competing thoughts on room design. Where most people screw up is that they mix and match between them without understanding the big picture. Pick your design philosophy and stick to it religiously. My best suggestion is to get a book called the "Master Handbook of Acoustics" by F. Alton Everest. This is pretty much the Bible of acoustics.
As for me, I found that 14x19x10 (Louden's Ratio) was the most ideal. My walls are 10" thick styrofoam/concrete and my entire roof is a pseudo helmholtz resonator. Add in a few more room treatments to further tweak the room and it is about as close to perfect as I could ask. Personally haven't seen/heard any room that was better.
Julian
As for me, I found that 14x19x10 (Louden's Ratio) was the most ideal. My walls are 10" thick styrofoam/concrete and my entire roof is a pseudo helmholtz resonator. Add in a few more room treatments to further tweak the room and it is about as close to perfect as I could ask. Personally haven't seen/heard any room that was better.
Julian