Panel placement for rear wall reflection problem

FWIW I always thought that the reason for bringing your speakers out into the room was fundamentally to reduce excess bass caused by rear wall reinforcement, not to reduce the magnitude of higher frequency reflections off the wall caused by speakers (although that can be a side benefit especially with dipoles). To answer your question, the panels should be placed on reflection points just as you would do for side wall reflections, essentially between the two speakers, not necessarily behind them. Another thought, is the use of dispersion for the back wall as opposed to absorbtion. Many folks prefer this manner of dealing with high frequency reflections, including myself, to deadening the wall.

Jb3, Trial & error is the only way to go, but many folks here, including myself, have a lot of pratical experience dealing with room acoustic's, but other than answer your specific question, its tough to help without further information about your "bright" room. If you want more help tell us about the size of your room, the size and location of doors, windows, openings. The location of your speakers in realtionship to the side walls and the rear walls and your listening position. Also include floor and wall furnishings and furniture such as bookcases, chairs sofa's etc. The more information you give the better the quality of the comments you will get.

Tough room - trial and error rules. The first thing you want to do is to try to deaden the first relection points as much as possible.I agree re the kitchen area being a major problem. Is there any way you can put something behind the sweet seat to absorb or deflect the reflections from this area, i.e. bifolding panels covered with heavy fabric, which you could fold up and put away when you aren't using them? Heavy drapes over the windows would be better than the blinds, but the blinds would be better than nothing, especially if when they are down they don't present a flat surface. On the 8ft section of wall on the left is their any space which you can treat (I like to use book cases filled with books of various sizes and irregularily placed)? Here is another trick to try which may not deaden the bright aspect of your room but could help with the clarity of the highs because it lengthens the time of arrival of the first reflections (and its counter intuitive as well as strange looking at first.) Play with the toe in beyond the normal "straight ahead to slightly pointed in". Cross the axis of the speakers in front of you 'til the axis of the speaker is pointed somewhere between your head and the adjacent wall. This could also help fill in the center of the sound stage and widen the listening position. Sorry I couldn't be more helpful.