First Listen: Dolby Pro Logic IIz Page 3


Stop the music!

After hearing what PLIIz does for the music in 5.1 movie soundtracks, I expected it to do some pretty amazing tricks with two-channel music from CDs. When I played my usual test tracks and switched back and forth between PLIIz and the standard Pro Logic II Music mode, I quickly found that I preferred the latter, no matter what music I was playing.

An e-mail to Dolby senior technical marketing manager Christophe Chabanne told me why. Chabanne said that PLIIz is based on the Pro Logic II Movie mode, not the Music mode. According to him, Dolby experimented with making a music-specific PLIIz mode, but couldn't get it to work to the engineers' standards.

PLII Music mode spreads some of the signal from the center speaker into the left and right speakers, in order to make vocals sound more natural. PLII Movie mode and PLIIz tend to collapse vocalists into the center speaker. It's an effect that works great with movie dialogue, but it makes singers on stereo CDs sound like they're stuck in a box. To me, listening to two-channel music through PLIIz just sounded weird and wrong.

Every PLIIz receiver also includes PLII Music mode, so you'll still have great listening options. My guess is, those who've been dying to hear "Free Bird" expanded to more dramatic proportions may like PLIIz's effect on stereo music. However, I would also guess that those who hoped PLIIz would enliven their jazz records or their old Steely Dan sides will be disappointed. And of course, they may wonder why they took the trouble to install those extra speakers.

A Sunfire CRM-2 satellite, on the height channel shelf.

Tweaking the setup

During my time with the TX-SR607, I experimented extensively with position and type of the height speakers. I swapped out the monopolar Sunfire CRM-2s for the bipolar CRM-2BIPs and Atlantic Tech 1400 SR-z. I moved the speakers across my shelves, from directly above the main speakers to over near the corners of the room.

I couldn't experiment with changing the height of the speakers, though. Dolby recommends at least three feet between the main speakers and the height speakers, so with a regular 8-foot ceiling doesn't leave much room for experimentation. I placed my shelves 82 inches off the floor, 15 inches from the ceiling, and 46 inches above the tops of my main speakers.

Sadly, my experiments didn't reveal dramatic results. When you're talking signals that are 20 dB down from the main channels, slight changes don't produce big differences. Even switching from the ribbon-tweetered Sunfires to the tweeterless Atlantics didn't make much difference.

In my room, at least, I liked the sound best with the height speakers directly over the main speakers. This produced a somewhat more focused, more exciting sound. Moving the speakers to the corners of the room increased the ambient effect a bit, but took away some of the impact.

And I slightly preferred the effect with the Sunfire CRM-2BIP than with the Atlantic 1400 SR-z, just because its sound better matched that of the Sunfire main speakers. But we're talking very minor differences here. I tried a couple of cheap speakers from an old home-theater-in-a-box system, and even those worked pretty well.

Thumbs up or thumbs down?

Even though Pro Logic IIz delivered a less exciting result than I'd anticipated, I'd prefer a PLIIz-equipped receiver or surround-sound processor to one without it. Why not? It's evident from the 2009 Onkyo and Denon lines that PLIIz adds little, if anything, to the price of a receiver, provided no extra amp channels are included. You don't need to invest a fortune in height speakers; anything decent will do. And in most systems, wiring those extra speakers will probably be easier than wiring an extra set of surrounds for 7.1.

Dolby's surprisingly modest goal with PLIIz seems to be merely to get some use out of those two rear-surround amp channels that typically go unused in a 7.1-channel receiver. In that, the company has succeeded. I don't think PLIIz will attract legions of fans or generate great excitement among enthusiasts, but it is better than what we had before. I like it.