When I was using two dipole speakers for the rear center, there were certain movies that were not encoded DD EX that suffered from rear center collapse. This would happen in DD EX Mode during effects intensive scenes. Since I have upgraded to four QS4s for the rear soundstage, I have noticed the same "blob" effect both to the side and sometimes the entire rear soundstage with both EX and non-EX movies. Anyone else experience this problem?

Can you describe the "blob"?

It seems to happen when there are explosions or when some sound effects pan from the front soundstage to the rear soundstage. The sound seems to fill the rear soundstage almost as if the rear speakers channel level trim is set incorrectly (too high relative to the other speakers). This may be the nature of quadraphonic speakers or the way the sound engineer intended it to sound; in either case it reminds of the problem I had when I had a home brew EX system. Sometimes the rear center effects would collapse making the rear center speakers louder than the other surround speakers.