gonk,

Neo:6 is used with DTS 5.1 soundtracks, but the process is more often referred to by another name: DTS ES decoding (the matrix version, not discrete 6.1). A little background if you will...

Like most matrix decoders, Neo:6 has a back part and a front part. The back part is where decorrelated (out-of-phase) sounds from the 2-channel input are steered. The front part converts 2 channels to 3 channels by extracting correlated (in-phase) mono info and steering it to the centre output. It is this front part that is used to extract surround-back content from the 2 surround channels.

When the surround-back channel first started to appear on DVDs, there was only one decoder: THX Surround EX, which used the front portion of the old Pro Logic matrix and could be applied to DD and DTS soundtracks (it still can be applied to both). After THX's exclusivity period was over, Dolby and DTS started marketing their own surround-back decoders. DD EX and DTS ES both continued to use the front portion of the old Pro Logic matrix for surround-back extraction. If you remember back, this was one of the things that caused the 950 to be delayed: Outlaw had an opportunity to include licensed EX decoding instead of some third-party surround-back extraction (like on the 1050 receiver).

Around this time, Dolby allowed DSP chip manufacturers the option to switch from old Pro Logic technology to their newer PLII matrix for surround-back extraction. Again, they would be using the front portion of the matrix to extract a mono surround-back channel.

DTS probably didn't want to keep licensing technology from their direct rival, so they switched to using the front portion of their own Neo:6 matrix to extract the surround-back channel of DTS ES soundtracks. You can still this reflected in the nomenclature of some receivers and pre-pros. For example: on Anthem processors, if the DTS 5.1 soundtrack is properly flagged for ES decoding, you'll see "DTS ES" on the front panel. If the soundtrack has no flag (irrespective of whether it is ES encoded or not), then you will see "DTS + Neo:6" on the front panel. Same thing, different name.