Looking for tips about speaker placement?

Hello. I made a thread about this a few weeks ago and forgot to provide dimensions. I decided to give the speaker placement another go (current setup is subpar), and am looking for advice since I'm very uninformed about acoustics. I would greatly appreciate any help.


The image on the right is the floor plan for the place I live in. I need to place the speakers in the "loft" area that seems to be very poorly optimized for speaker placement. Here is a more zoomed in sketch:
http://postimg.org/gallery/5aal3hf6/33275ec3/ (actual pictures)

The right "wall" connecting Junctions B and C stops short 40-45 feet from the floor. One can lean over and see the floor below, and there is thus an enormous expanse of open space.

The reason why everything below Junction C is off limits for placement, is because despite the solid line I drew at the very bottom, there is an irregular area including a washer/dryer, a bathroom, and an opening for the stairwell. I'm not sure it would be good to have sound reflect off that area.

The approximate (accurate within 3 inches) dimensions are as follows:

Corner A to Junction B - 98 inches
Junction B to Junction C - 113 inches

Would it be better to retain the current setup with adjustments or place the speakers against the shorter (real) wall and deal with asymmetry from the open space and lack of a rear wall? Should I get some cork tile and put a board instead of a mattress? Any other suggestions would be awesome.

Thank you very much.
Do yourself a favor and get a hold of a Test CD such as the XLO Test CD that contains a speaker set up track. This is the most accurate as well as least time consuming method of determining speaker location in ANY room. The main problem with other methods is they are essentially trial and error. I.e., you never know when you have found the real optimum locations.