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DTS Extended Surround (Matrix or Discrete 6.1)
DTS Extended Surround refers to the Digital Theater Sound's version of the new "6.1"-channel surround sound format that extends the 5.1-channel surround sound format with one (or two) additional speaker(s) located in the back of the audience (i.e., back surround channel). DTS Extended Surround (or DTS-ES for short) comes in two flavors: (1) DTS Extended Surround Matrix, or (2) DTS Extended Surround Discrete 6.1.
DTS-ES Matrix is actually a 5.1-channel format with the back surround audio channel matrixed into those of the right and left surround. The back surround channel is matrixed in similar fashion as the front center channel is matrixed into the front right and left channels in the Dolby Surround Pro-Logic format. As such, the back surround channel is not discrete and therefore is not a true "6.1" format. DTS-ES Matrix is compatible with THX Surround EX equipment. DTS-ES Matrix is completely backwards compatible with DTS 5.1 equipment.
DTS-ES Discrete 6.1 is a true 6.1-channel format, as the back surround audio channel is discretely encoded into the DTS bitstream. This format offers better spatialization over the surround channels for complete 360-degree sound localization and surround pans (i.e., movement of sound in the surround channels from one side to another). A data flag signals the decoder (usually part of the receiver or pre-amplifier) that the bitstream contains an extra discrete back surround channel. For backwards compatibility, DTS-ES Discrete 6.1 back surround channel is ignored by DTS 5.1 equipment.
What about the extended surround "7.1" format? Well, "7.1" is not a true surround sound format. Rather it refers to home theater equipment manufacturers' proprietary implementation of two back surround channels using the same back surround audio signal that was discussed above. Usually, the audio signal fed to the two back surround channels are identical, but some manufacturers may choose to mix some information from the left and right surrounds. Again, these are proprietary implementations that vary across manufacturers and are not industry standards. The use of two back surround speakers fills in the sound better from the rear of the audience than single back surround speaker implementations.
To take advantage of DTS Extended Surround digital surround, you must have both:
(1) DTS-capable DVD player, either with DTS digital output or a DTS built-in decoder. Look for the "DTS" or
"DTS digital out" logos on the faceplate of the DVD player.
(2) DTS Extended Surround decoder, usually part of a DTS-ES capable receiver or DTS-ES capable pre-amplifier.
Look for the "DTS Extended Surround" logo on the faceplate. THX Surround EX equipment can decode
DTS-ES Matrix, but not DTS-ES Discrete 6.1. DTS-ES Discrete 6.1 requires a true DTS-ES decoder.
Equipment featuring a true DTS-ES decoder is still few in number and are expensive. A few models that are
currently available include the Denon AVR-5800 receiver (approximately $3,800).
THX Surround EX is a competing extended surround matrix format. Currently there are no THX or Dolby Digital equivalent of DTS-ES Discrete 6.1.
Also see: Surround Sound
Formats page for a full explanation, DTS, THX
Surround EX, Dolby Digital
Additional Information and Reference: DTS Digital Surround home page
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