When 7.1-channel surround sound came out a few years ago, no one knew if people would buy it. And no one knew if Hollywood would produce 7.1-channel soundtracks. But there's one thing everyone knew: Someday, somebody would come up with even more channels.
That day will come this spring, when Onkyo introduces the first of six receivers featuring Dolby's new Pro Logic IIz technology. The "z" in Pro Logic IIz signifies the Z axis, otherwise known as height. To a 7.1- or 5.1-channel system, Pro Logic IIz adds two speakers, both positioned at least 3 feet above the left and right front speakers. Dolby's senior manager of partner marketing Craig Eggers, describes it as "a way to increase envelopment and get more depth, more dimension, more airiness."
Not everyone is excited about adding more speakers to today's dauntingly complex home theater systems. "The confusion this will generate further erodes the credibility of the industry," says Parasound president Richard Schram. "It's another example of a gratuitous feature that consumers won't understand."
To find out if home theater speakers really have nowhere to go but up, I traveled to the Software Test Lab at Dolby headquarters in San Francisco, where I sat through an extensive demonstration of the new technology. I got to try height channels in practically every possible permutation and with all types of software. In the process, I answered most of my questions - and found a few interesting surprises.
According to Dolby senior technical marketing manager Christophe Chabanne, Pro Logic II technology always had the capacity to create more channels. The problem was, no one knew which channels to add. Of the more than 20 possible speaker positions specified by the Society of Motion Picture and Television Engineers, Dolby found that only front height speakers consistently impressed test subjects. "The wiring is easy that way, too," Chabanne pointed out.
Most height-channel content in Pro Logic IIz is ambience, such as what you'd hear echoing off the ceiling of a concert hall. PLIIz extracts ambience by looking for sounds that appear in all channels but don't have a particular focus.
However, the height channels can carry directional cues, too. "If PLIIz sees something that's in all the channels but is a little more in the left channel, that would go up into the left height speaker," Chabanne said. "The most important thing is that information that's primarily in one channel won't appear in the height speakers. You won't hear things like footsteps or dog barks coming from them." You also won't hear any reverb or frequency filtering.
Like other variants of Pro Logic II, Pro Logic IIz simply steers sounds; it doesn't alter them. It's possible to encode material specifically to take advantage of PLIIz's height channels. Hollywood studios have rejected the height-channel option, but according to Chabanne, reception in the gaming industry has been enthusiastic. "None of them have committed to it yet," he said, "but I wouldn't be surprised to see titles appear soon."
For games, the Pro Logic IIz encoding software is included on the disc and loaded into the console when the disc is inserted. Chabanne said PLIIz encoding will work on practically any game console, but is currently best suited for PlayStation 3 and Xbox 360.
At press time, only Onkyo had announced specific plans to produce A/V receivers incorporating Pro Logic IIz. Onkyo product manager Brian Sandifer said the receivers will come in two types: 7.1 and 9.1. The 9.1 receivers will have nine amplifiers, for driving a full 7.1 system plus the two height channels. The 7.1 receivers will have seven amp channels, which can be used for conventional 7.1 or for 5.1 with height channels added. Peter Tribeman, president of both speaker manufacturer Atlantic Technology and electronics company Outlaw Audio, likes the idea of repurposing surround speakers for height channels. "In my opinion, the benefits of conventional 7.1 are marginal," he said. "Applying those channels to height speakers in the front has a profound effect. All of a sudden, it goes from three front speakers to a total re-creation of the stage."
Tribeman is enthusiastic enough about the technology to have created an Atlantic Technology speaker specifically for height-channel use. But Dolby's Eggers says any standard surround speaker will work fine for the height channels as long as its sound matches that of the system's other speakers.
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