I have the Yamaha RX-Z9 9.1 and can tell you that correctly selected and installed loudspeakers (based on your environment) improve the sound, and in my opinion the DTS being the better tech.
The sound field are thus;
5.1 channel surround sound format is five discrete (independent) channels (front center, front left, front right, surround left, surround right; giving it the "5" designation) of full frequency sound (with respect to the range of human hearing, which ideally ranges from 20 Hz to 20,000 Hz), plus a sixth channel for low frequency effects (LFE). The LFE signal is usually reserved for the subwoofer speaker(s), or those speakers capable of reproducing low frequency ranges. The low frequency effects channel gives DTS the ".1" designation. The ".1" signifies that the sixth channel is not full frequency, as it contains only deep bass frequencies (3 Hz to 120 Hz).
Extended Surround formats: Dolby Digital EX & DTS Extended Surround (DTS-ES)
The difference between the new Extended Surround formats and their 5.1-channel surround sound counterparts is the addition of a surround back channel, whose corresponding speaker is placed behind the audience. This allows certain soundtrack effects to be presented behind the audience, thereby achieving more enveloping and complete 360° surround sound. (Remember that in the 5.1-channel surround sound formats, the surround speakers are placed one on each side of the audience - not behind them.) Additionally, while the Extended Surround sound format calls for one surround back channel, two surround back speakers are generally recommended for better envelopment. Acknowledging this widely accepted industry position, some high-end receiver manufacturers have introduced "7.1-channel" capable receivers, with decoding and sometimes amplification for the two extra surround back channels.
Both encode the surround back channel information into the surround left and surround right channels (similar to the way the center channel is encoded for Dolby Surround Pro-Logic). This cross-channel encoding is referred to as matrix encoding, since the surround back channel is encoded and later decoded (or derived) from those of the surround left and surround right channels. Because of this matrix encoding scheme, the surround back channel is not a true discrete channel and is technically considered a 5.1- channel format. And for this reason, they are sometimes referred to as "Dolby Digital 5.1 EX" or "DTS 5.1 ES". To refer to these matrix encoded Extended Surround formats as 6.1-channel would be wrong. Both have some offering of TRUE discrete 6.1 encoding; but additional channels are all matrixed not encoded on the discs..
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A correct full 7.1 loudspeaker placement. DD Sounds good, but not the best. DTS specializes in “master quality” soundtracks with far less compression. 8.1 and 9.1 systems add the single rear center and dual rear center between the two back surround L/R. They are only matrixed, not encoded material on the disc.