a bit confused regarding correct surround back speaker placement

[RocShemp]

I'm a bit confused regarding correct surround back speaker placement in a 7.1 setup.

I have an Onkyo TX-SR705 that I am currently using as a 5.1 receiver because I currently don't have the surround speakers I want to movie into 7.1 surround. Also, space is an issue. I'm thinking of resolving that by using some in-ceiling monopoles as my surround back speakers. But that's a question for another time.

My current confusion is regarding at what friggin' angle I'm supposed to place the surround backs. Some suggest closer and others farther. To add to my confusion, today I was at the THX website and they have two very different suggestions for surround back placement but not actually as options.

Let me explain via quotes from the website.

The left and right surround back speakers are direct firing, placed together on the back wall to take maximum advantage of THX’s patented Advanced Speaker Array (ASA) technology. Using this speaker setup, THX ASA digitally reconfigures the surround channels to recreate the appropriate sound fields for movies, music and games.

If the SBL and the SBR can't be placed together, refer to the pre-amplifier or receiver's "THX Setup" menu for alternative configurations to maxmize your system's potential.

http://thx.com/home/setup/speakers/back.html

It's very different from what others have suggested but that's not the weird part. At the bottom of that page is a link that reads "Click here for Dolby® TrueHD or DTS-HD™ room setup information." This leads me to the following bit of information.

If you have an AV receiver with the ability to decode Dolby TrueHD and/or DTS-HD, and you are playing 7.1 discrete content, then you will want to separate the back surround speakers to produce a 60 degree angle from the main listening location.

In addition, you should make an adjustment to your receiver setting. Simply go to the THX Setup Menu in your THX Certified AV Receiver/Pre-amp and set the ASA Surround Back Speaker setting to "Apart (greater than 48)."

http://thx.com/home/setup/speakers/dolby.html

Am I expected to move my surround back speakers depending on wether I'm listening to discrete 5.1 or discrete 7.1 content? Or the fact that my receiver can accept and decode discrete 7.1 content mean that the ASA configuration is totally wrong for me? Does that also mean I should not use any of the THX modes?

[SlmShdy1]

The THX option is suggested, by THX I might add, as long as you have THX certified speakers. I would more than likely go with one of the diagrams found on Dolby's or DTS' website.

You shouldn't have to move your speakers between a 5.1 and 7.1 setup. As long as the player is outputting the correct number of discrete channels, you'll be fine. The PS3, on the other hand, will sometimes output a 5.1 track in 7.1 channels of sound, resulting in incorrect speaker placement because your sound for the rears will come out of the sides. So if you want to hear the correct placement of a 5.1 track, you have to deselect all 7.1 options.

The ASA configuration, I wouldn't use unless I had THX certified speakers. As far as the THX modes go, most users here prefer not to use them because it alters the original audio source.

[RocShemp]

Thanks, SlmShdy1. I've been using the THX Cinema mode since I like the Re-EQ. It's more pleasing to my ears since I have bare walls and floors. Even after running Audyssey (which itself has it's own high end rolloff), I find the Re-EQ in the THX Cinema mode tames the high frequencies more to my liking.

So I'll just choose to the Dolby/DTS configuration with non-THX certified speakers but choose the ASA configuration if end up getting THX certified speakers. Again, thanks for the help.