Okay so I understand the concepts but not sure how it really plays out. I currently have 6.1 setup in my home. I have Blu-Ray and HD DVD players. I also have an Onkyo 875 capable of processing Dolby True HD and DTS HD-MA. My question is until now there hasn't been any 7.1 or 6.1 material.

My understanding is that the receiver when playing 5.1 material simulates 6.1 by sharing the rear left and right sounds to the center rear.

Now there is 7.1 material (still no 6.1). So what will happen with 7.1 material in my 6.1 sound setup?

And am I correct that 5.1 is simulated to 6.1? I would love an explanation. Thanks in advance to all of you.

My understanding of 7.1 audio (and it could be wrong) is that the two surround back channels both carry the same information. That basically, any 7.1 material is essentially 6.1, with the 6th channel getting sent to two speakers in the back of the room. So, if my understanding is correct, you won't be missing any content with a 6.1 system.

DTS-ES is a 6.1 mix. 6 discrete channels, plus subwoofer.

Dolby TrueHD is capable of 7.1, I'm not sure if any movies have actually used all the channels though.

A 5.1 source will take the two rear channels and matrix them together to create a rear center channel. I believe from there to 7.1 is just a matter of sending the rear center channel to two speakers.

With a 7.1 source on a 6.1 system I would assume the two rear channels will just be combined.

IMO unless you have a very large room you're not going to hear much difference between 5.1 and anything else. Assuming the acoustics of the room are decent and the rear speakers are properly set up.

My understanding of 7.1 audio (and it could be wrong) is that the two surround back channels both carry the same information. That basically, any 7.1 material is essentially 6.1, with the 6th channel getting sent to two speakers in the back of the room. So, if my understanding is correct, you won't be missing any content with a 6.1 system.Unfortunately, there's no consistency. On DVD, 6.1-channel material was delivered as 6.1 channels. On HD media, like Blu-ray, there are 7.1-channel soundtracks where the 2 surround-back channels contain dual-mono content and ones where they contain real stereo content. Whether the soundtrack was 6.1 or 7.1, the surround-back channel(s) should be played back using 2 rear speakers. A 5.1 source will take the two rear channels and matrix them together to create a rear center channel. I believe from there to 7.1 is just a matter of sending the rear center channel to two speakers.Depends on the matrix technology used. EX/ES decoding extracts a single surround-back channel, sent to both rear speakers as a dual-mono signal. Pro Logic IIx processing extracts stereo surround-back channels, so that the 2 rear speakers are playing different content. Whether you're extracting mono or stereo surround-back channel(s), it should be played back using 2 rear speakers. IMO unless you have a very large room you're not going to hear much difference between 5.1 and anything else.Even in a small room, if you can tell the difference between sound coming from your sides versus sound coming from behind you, then you'll be able to hear the difference between 5.1 and 7.1 playback.

Sanjay