Quote Originally Posted by Sir Terrence the Terrible
Regardless whether you use six, or seven speaker, the collaspe to the rear will happen unexpectly on non EX encoded soundtracks. With seven speakers(epecially if they are spread far apart) the collasping will be much less localized, and therefore not readily noticed. Regardless, that is not what the re-recording engineers desired. The way the matrix works for EX signals makes this unavoidable. That is why EX signals have to mixed a certain way, and monitored during mastering. This prevent signals from jumping or moving in unpredictable ways.

Using a EX decoder on unecoded signals is a hit and miss thing. There is always a chance for signals to pop out in unexpected directions, or just collaspe the soundfield rearward.

Using a circlesurround decoder desolves all the problems associated with using a EX decoder. Since it processes the center fill totally differently, it can be used on even non EX encoded signals, and retain spatial accuracy.
Intersting input, Sir Terrence...I can't think of any particlur 5.1 encoded scenes that force a collapse to the rear as you suggest. But this would describe adequately that which I found a bit annoying for the few weeks I tried 6.1. I had to lower the level to the rear a bit to compensate to my liking.

In my "7.1" setup, my rear speakers are placed almost perfectly opposite the front mains, toed in. When appropriate I get a decent rear center image, but mostly just ambience...I'm guessing their about 10 feet apart, and 8 feet from the side surrounds.
No localization occuring. Most of the time I find it "delocalizes" the side surrounds if I switch back and forth creating a more ambient side rear field...hard to describe.

I would be interested to know of some specific scenes from movies where there is a noticeable detriment to the surround field in a non-Ex encoded soundtrack. Are you (or anyone else) aware of any?