The back wall is not a bad place. Especially if your close to it. I do suggest you put one at the 1st order reflections if you can, but if it already sounds great then don't worry about it.
Thx, I actully have 2 windows (basement) on the left side wall which I have hung floor to ceiling curtains on. This helps with the first order reflections. For the Right side, there are two sets of stairs, one up, one down that are open. I am thinking of at least putting a curtain blocking the entrance to the stairs going down. (FYI - I have a 4 level backsplit)
I am sitting 8 feet from my back wall. I may place one more panel on it, have not decided yet. Still need to decorate as well.
My room is L shaped.
Front - 14ft
Left - 22ft
Back - 22ft
Right (from Back wall forward) - 8ft
Right side from front has a small washroom (big bass trap), stairs going up, staris going down.