Ok. I should really be good at this by now. As I understand, to date, there are no 7.1 DVD's because there are no 7.1 recording studios, no?

So, in order to "7.1" a theater we set the soundfield to PLII, or DTS EX. The back speakers then sing in a cool sort of way from either 6.1 software (The 5th Element and Old Yeller whatever) or kindof jazz up the 5.1 or 2 channel stuff. I didn't get much of any kick at all out of the last system we set up. It was in our perfect venue - a great room with existing rear/back speakers in ceiling etc.

So... why not output all 4 rear speakers in parallel from the standard 5.1 surround outputs rather than using the "Surround Back" terminals for the back speakers? Don't you find this gives a more uniform sound for great 5.1 effect overall? Or do I owe this client an apology?

Once again, does the emporer have his clothes on or doesn't he? I'm with you guys.

It depends on what is headed to the "surround back" terminals from the processor.

With a true 6.1 encoded DTS ES or DD EX DVD, you will have a discrete rear feed that will be shared. Depending in the processor, de-correlation will be applied to give the illusion of seperate left and right information.
Any processor with THX post processing will have a THX EX mode that will do this for the DD EX discs.

If the signal is plain old 5.1, 4.0, or even 2.0, the processor has to come into play again to determine what sounds go to which speakers and with what processing applied. Many procesors will take the surround signal and create a seperate side and rear signal from each input and time shift them slightly to create a soundfield that pans smoothly from front to back, back to front, and corner to corner.
Obviously there is a "garbage in, garbage out" rule here.... your Magnum PI box set wil not have the same effect as Gladiator, Star Wars Episode II or the "extended cut" versions of the LOTR films that all have discrete 6.1 soundtracks on DVD.

Some do it better than others, and the better processors like Lexicon allow you to dial in the amount of processing to tailor the effects to the speakers and your room. A small room with direct radiating surrounds may sound better with a little more processing, whereas a large room with a lot of dipoles probably already acheived the spacious and enveloping effect, and the amount of digital processing can be dialed back slightly.

Lexicon has had a 7 channel mode since the early 90s, Logic 7, and I still use the Logic 7 modes more often than any others.

I think you would be more likely to owe them an apology if you wired the system for 5.1, with speakers wired to the same outputs.
Then they will be missing out in the discrete information on the 6.1 ES and EX encoded DVDs like the ones listed above.

Go here to see what kind of titles are going to show off these extra speakers in the best way possible.
[Link: dtsonline.com]
[Link: widescreenreview.com]

You mean I'm not going to get great sound from my A-Team and Dukes of Hazards DVDs?

Sure, but you have to bang your head against the wall a few times....
The ringing in your ears will sound as if it is coming from all directions.

I appreciate the explanation. I have the Yamaha RX-V650 w/B&W's in our home with 7.1. The "Theater Room" is downstairs in a 14x17 area, carpeted etc. Star Wars and a few others really sound amazing but TV (Cox Cable 3250HD) and quite a few DVD's (even many of the new ones) are quirky. Some DVD's seem to sound better when not played in DTS - kind of a trade off.

The great room area soundfield seemed a lot more predictable by tying the array into 5.1 (older in ceilings, the rears way far outside and the backs just behind and over the listener, B&W bookshelfs in front). I installed the RX-V1500 THX Select and did a manual setup. It certainly kicked the old RX-V995's tail.

Any suggestions on how to make a 7.1 more consistant or am I discovering their is something missing in a receiver under $1000?

For anyone who wants to feel smart about 7.1 before they get confused this is good place to begin:

[Link: dolbylabs.com]

Good grief, I'm noticing the propeller on my hat is a little bent. I hope nobody noticed.

In the old days it wasn't uncommon to wire two pair of speakers to the rear ouputs if the room was long enough to warrant the extra set. Considering what a sketchy job some of these receivers do when interpolating 5.1 media into a 7.1 system it doesn't supprise me at all that some people would end up going back to wiring two sets of rears and putting the receiver into a 5.1 mode.