Joel-
I would suggest that you read Todd Welti's research article on optimum subwoofer placement.
http://www.harman.com/wp/index.jsp?articleId=1003
Don't worry about your room not being perfectly rectangle since as Dr. Floyd Toole teaches in his CEDIA seminar, the "perfect rectangular room" doesn't really exist. Once you add a door or window into a room all the theoretically correct placement of subs goes out the window.
You will see in Todd's article that equalization can help immensely in allowing placement where it's convenient to you (and not the subwoofer) in smoothing out the Max and Min deviation of frequency response that you'll inevitably get at the listening position.
The introduction of EQ into the system leaves you with 3 alternatives:
1) Buy subs which have single band parametric equalization built-in such as some Infinity or Velodyne models or some models from AV123 or the just introduced JL Audio home subs. At the AES show on which I reported Bag End has supposedly filed for a patent on their version of a room subwoofer EQ system. The 12" home version of this sub will not be available till 2005.
2) Using a Behringer outboard parametric equalizer may also get the job done (and handle 2 subs). I've got one on hand and will be reporting on how well it works in the near future. I will say though that it appears that you may also need a lot of set-up chops to be able to make this unit work properly since the auto Feedback Destroyer function insets only a very, very narrow dip circuit which in most cases will not completely eliminate a problem frequency which may have a wider bandwidth room boost.
3) the SOS unit available through Speaker City got a Product of the Year Award through one of the print mags because it can automatically run its equalization routine with an included microphone once your sub is placed where you want it in the room.
At $299 each you would need 4 of these units. Prez Gene has confirmed to me via a before-and-after graph that this unit really does work, and work well. His only reservation is that one of his two units may have not worked out of the box and the second which did work well caused a turn-on pop through his system. So the SOS may need to be plugged into a line conditioning unit.
Both of these units are on their way to me so I will also be reporting my findings.
http://www.speakercity.com/Sos/SubwooferOptimizer.shtml
