Modes and Trapezoids | John Sayers’ Recording Studio Design Forum archive

I have a 16'4" x 20'1.5" basement room in which I am building a one room project studio (it will also be my office). I have enough ceiling height that I can build a room-in-a-room with a ratio of 1:1.51:2.14 with 9'2" ceilings. Before going down this path I want to consider the possibility of a trapezoidal room. There are practical reasons (such as access to existing windows) that make me reluctant to go this route, but before deciding I want to understand the acoustic repercussions of the alternatives. 1) Is it important that the average width of the trapezoid exactly match a desired ratio for mode calculation? Or is the desirability of certain ratios of minimal importance in a trapezoidal room? Or perhaps it is the width of the room at the mixing position which should match an “ideal” ratio? 2) I’ve seen 12 degrees specified as the desirable total angle (each side wall splayed 6 degrees). How vital is this value? I would only be able to achieve half of that (3 deg. per wall) if the average width is to match the desired ratio for modes. 3) In my fixed space, the trapezoidal room will have less cubic volume than the rectangular. Is this a trade off worth worrying about? I’m over 2000 cu. ft. in any case, but I have heard that 2500 cu. ft. is a desirable minimum. BTW, more details on my room can be found at http://johnlsayers.com/phpBB2/viewtopic.php?t=11196 Thanks in advance!