Dolby has a new surround format: Pro Logic IIz.
Here we go again. Another new format with more speakers, but this time, the "surround" speakers are in the front of the room, three or four feet above the left-and right-main speakers. These height channels are designed to provide a greater sense of envelopment than previous generations of Dolby or DTS surround.
Pro Logic IIz incorporates all of the features and capabilities of Pro Logic IIx.
"Expanding on established Dolby Pro Logic II matrix-decoding innovations, Dolby Pro Logic IIz identifies and decodes spatial cues that occur naturally in all content--stereo and 5.1 broadcast, music CDs, DVDs, 5.1 and 7.1 Blu-ray Discs, and video games," the Dolby site further explains. "Dolby Pro Logic IIz processes low-level, uncorrelated information--such as ambiance and some amorphous effects like rain or wind--and directs it to the front height speakers."
You don't have to buy new, specially encoded discs to experience Pro Logic IIz, but do you really want to buy another pair of speakers, wall-mount them, and run a pair of speaker wires up your wall, to the sides of your TV?
Dolby doesn't require the height speakers to be identical to the main-left or -right speakers. Some Pro Logic IIz systems will use a total of nine speakers (five front, four rear), plus one or more subwoofers.
Onkyo's TX-SR607 ($599 MSRP) is the first receiver to feature Pro Logic IIz; the company will soon offer additional models equipped with the new Dolby processor, to be announced later this year.
Then again, Yamaha's higher-end receivers have had height, aka "Presence," channels for years. Those extra speakers supplement the sound from the front speakers with ambient effects produced by Yamaha's proprietary Cinema DSP, which provides various multichannel configurations up to 11 channels. Obviously, Dolby's Pro Logic IIz uses different technology, though the end result may be similar.
I haven't yet heard Dolby Pro Logic IIz, but I have a lot of experience with Yamaha's system. The Presence speakers really do "open up" the front sound stage and provide greater depth. This, in some ways, makes more sense than rear-surround channels; most listening rooms don't have enough space behind the couch for rear speakers. Extra front speakers seem to better correlate to the onscreen image (the visuals are in front of you). Pro Logic IIz or Yamaha presence speakers don't replace side- and/or rear-surround speakers.
Then again, if the idea of doing more with less appeals to you, consider the stereo home theater option, aka HT 2.0.