Originally Posted by Kain
Sorry, but I have a slight off-topic question...
They say that sitting right in the middle of the room is bad for bass as it is supposed to be a null. But how come I see quite a few high-end home theaters where they have some row(s) or even the "main" row right in the middle of the room? How are these setups "avoiding" the bass null?
You are correct. Middle of the room, along with 1/4 lengths/widths are less than optimal seating positions due to modal issues, resulting in peaks and nulls at frequencies dependent upon the room dimensions. The peaks can be tamed by proper subwoofer placement of course, and it is the ringing/modal decay problems that are the most audible and offensive. Sometimes something that looks like a null is really just lack of modal support between two peaks. Knock those peaks down, and things sound much better. If following the Welti/Devantier method for multiple subs, you can control several room modes, and set up consistent seat to seat response, so global PEQ can be be effective also.
When looking at room drawings, such as the one Ash posted, make sure you are looking at total room depth. If you look at the screen wall, his seating does appear to be middle of the room, but are actually properly placed. I'd have to pull up his as-built drawings to see if moving his seating forward is a good idea acoustically. I would find his proposed seating placement a little too close for my tastes. SMPTE THX CEDIA etc reference seating distances are all around 43° to 50° or so. At close to 1:1, his current viewing angle for 2.39 is pretty close to 50°.
I don't think I would recommend moving the seating closer. It would put the seats very close to the middle of the room, video angle would get getting close to minimum recommended, and I believe the 3D audio immersion would suffer as well, unless the columns hiding the speakers were also moved forward.