The Dolby Web site is bubbling with excitement about its new processing trick, "With Dolby Pro Logic IIz, rain in a movie now seems to be actually falling on the listener's roof, concert videos bring a more intense sense of being at the performance, and orchestral works deliver more palpable depth, power, and connection." The "z" in Pro Logic IIz signifies the Z axis, otherwise known as height.
Sounds interesting, but when I setup and listened to the first receiver (an Onkyo TX-SR607) with Pro Logic IIz, the height speakers didn't lift my spirits.
Pro Logic IIz can, depending on the receiver's capabilities, either augment a 5.1 or 7.1 channel speaker system with two height channels. In other words, in a 5.1 channel system with Pro Logic IIz you'll have five speakers in the front of the room--left, center, right, left height, and right height--plus a surround speaker to both sides of the main listening position.
The 7.1 system with Pro Logic IIz uses the same speaker array--plus two rear surround speakers.
Once you have a receiver equipped with Pro Logic IIz, and wall mount the height speakers three feet or higher over the main left/right speakers, you're all set. You won't have to buy specially encoded movies or music.
According to 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. Dolby Pro Logic IIz processes low-level, uncorrelated information--such as ambience and some amorphous effects like rain or wind--and directs it to the front height speakers."
Nice idea, did it actually work?
Well. no. The height speakers didn't make a discernable difference. I couldn't hear them at all, so I increased the height speaker volume by 3 Decibels. Still no difference.
My listening position was about eight feet from the front speakers, but when I stood up and moved much closer to the front speakers I heard the height speakers. At that point my head was closer to the height speakers than the left/right front speakers. Moving back to the couch the height speakers' sound faded away.
We've listened to 7.1 many times before, and know it's a fairly subtle improvement. So unless your room is really large, with space behind your couch, seven channel isn't likely to create a more immersive, wrap-around soundfield than 5.1. In fact, I'd recommend sticking with 5.1, but take the money you would have spent on the height speakers and buy better main, left/right speakers. That's an improvement you won't have to struggle to hear.
If you already own decent left/right speakers, and you're still itching to spend money add a second subwoofer. Two subs can make a substantial difference.
Editors' Note: CNET will have a full review of the Onkyo TX-SR607 later this month. Prospective buyers should note that the receiver's Pro Logic IIz setup is optional--it will also work in standard 5.1 or 7.1 configuration, without the front height speakers.