Moving up from 5.1 to 7.1

[Woochifer]

I'm not as sold on the timbre matching though. I have 7 speakers from the same line now, but I didn't always. You can quite often get away with incredibly pleasing results using non-matched speakers as rears in a 5.1/6.1/7.1 setup (too big a difference would suck though). It is, however, very critical that the front 3 speakers be matched as closely as possible.

I agree with you to a point. With most movie soundtracks, the front and back sound elements are kept sufficiently separate such that timbre matching between the front and surround speakers is not as critical. However, with multichannel music and an increasing number of movies, more of the sound elements are mixed into the front and surround channels at nearly equal levels. With those soundtracks, timbre matching is a lot more important because mismatches sound much more distracting when all of the speakers are reproducing the same sounds.

I frequently turn the surround backs off so I'm running in 5.1 mode as a comparison, and I can honestly say, I cannot think of one situation where it the sound wasn't improved at least a tiny bit. There are some movies that don't really make much difference (dialogue intensive movies like JFK without special effects). Anything with good ambient soundtracks or a few special effects really comes off sounding better. And the odd time you do get a 6.1 encoded DVD, the results are even better still.

If you repositioned the L/R surrounds so that they are more to the side than slightly behind the listening position, it will sound fine with the back surrounds active, but leave a fairly large hole in the rear soundfield with the back surrounds switched off. I'm presuming that you use direct firing surround speakers.

Also, it really depends on the soundtrack, not just whether or not effects are in the surrounds. With a 5.1 soundtrack that has a more or less monophonic mix in the surround channels like Raiders of the Lost Ark, Glory, or Lawrence of Arabia, the EX/ES decoder will collapse a lot of sounds into the middle, and in those instances I don't think that 7.1 playback would be beneficial.

2 more speakers is a hefty chunk of money though. Make sure your room dimensions and decor (WAF) can accomodate such a setup though. I have no doubt poorly placed speakers would really suck.

And definitely, make sure you've gone as far as you can with 5.1 before adding more speakers.

Good advice. As you add more speakers, the level of complexity with optimizing the setup increases. The back surrounds represent two more opportunities to mess things up! That's why I question whenever people claim that they don't need a SPL meter to do the level calibration on a multichannel setup. With a two-channel setup, it's easy to tweak with the system by ear, but going to 5.1 or 7.1, you need to account for a lot more variables and compensating adjustments (i.e. delay timing, positioning, etc.).