Used to be I would hear Dolby Ex 6.1 and DTS ES 6.1 were out, and I read that it used a center surround back speaker to improve the entire surround effect dramatically in theaters, and since 2000 in the home. Now that I'm getting a 7.1 receiver I'll have the option to go 6.1/7.1 in the future (but not now, no room for SB speakers yet). I like to have total understanding of these things before moving onto them. But exactly how does it work? I've been reading a little on this but I want to make sure I have it right... so here it is: Dolby Digital EX (THX Surround EX) is it... A). A 7 channel encoding (6.1) that adds the surround back channel to the mix, thus increasing the 384, or 448 kbps bitrate to something higher? B). A 5.1 format that has a special remix on the two surround channels that can be matrixed into 6.1 without having to increase the bitrate. C). Geoff... you're totally off, or just a little off... what it really is is *(your answer here)* As for DTS ES I think I understand it. There is DISCRETE that is a true 6.1 and would slightly increase the 768kbps or 1.5mbps bitrate a little. and DTS EX MATRIX being that encoding on the surround speakers to derive the 6th surround back channel from. Right? In theory, with the higher bitrate, and being fully discrete, wouldn't DTS ES Discrete be the best quality for a 6.1 system? Also, with a 6.1/7.1 system, a standard 5.1 mix can be matrixed to fill all speakers, correct? So how does this sound? Thanks for the clarification. I just like to make sure and have all the facts. Any additional details would be nice too.