Have you tried/how do you feel about renting a pro sound loudspeaker processor so you can use an RTA to find a placement with halfway smooth bass response. Then use the eq to find out if flat power response around the room makes up for your reverberant field issue. I realize normalizing the frequency domain behavior by itself does't address the real issue of reverb arrival and decay times, but it's your first clue to what is going on in there. It can help find standing waves too. In my case this "correction" fixed the problem to my satisfaction. I bought the processor because it was a powerful tool. I left it hooked up because it was better than anything I had ever done to my system. some may hate the idea, or even the reality of the result. It may not be for everyone, but I am happily done with it. A couple of sheets of fiberglass framed behind tapestry art and a blinky metal box did the trick quite well. Is the room really fixed, no, can I really tell, no! If however you are a fan of analog or hate the idea of even a digital eq, note that in my case the ability to see what was happening, allowed me to find a setup that is much better even without the processor(hence renting one first) and may work for you just that way. I thought I had tried it all untill I could see it happening. We put the speakers on dollys and rolled them around like a giant tone control, only we could move the mic and see the total power in the room, so not to create more problems than we fixed. I am far from acoustics expert, but I am starting to see first hand what all those JBL white papers about D.I. matching and flat power response in the coverage area are all about. As an aside, taking your speakers outside and RTA-ing them will leave no doubt that Wayne has a real handle on things too.

Thomas