Audio Video News

My, surround sound, how you've grown. I remember when you were a wee bairn of 5.1 channels. Then Surround EX added up to two back surround speakers, Dolby Pro Logic IIz added two front height channels, and now those wild men at Audyssey are talking about two front width channels, for a potential maximum of 11.1.

Where exactly do the width channels go? The regular front left and right channels are positioned at 30 degrees off center, in the Audyssey scheme of things, and the width channels are another 30 degrees out, for a total of 60 degrees off center. Audyssey also specifies a total of 45 degrees off center, and another 45 degrees upward, for the height channels.

Why width? Audyssey's DSX primer explains: "Research into imaging showed that spreading the front channels wider than the standard ±30° results in a greater difference at the two ears and produces more envelopment. In concert hall acoustics this is called Auditory Source Width and, increasing it, is a desirable feature. But increasing the spread beyond ±30° for the front speakers was found to cause many imaging problems. This fundamental tradeoff in 5.1 surround sound systems between better frontal imaging and improved envelopment is a limitation."

Pragmatic minds will ask: Do you really need all those channels? Audyssey calls DSX a "scalable system" with a certain prioritization behind it: "Experiments have shown that human localization is better in front than to the sides or behind. This means that for front-weighted content such as movies and most music, good engineering dictates that we employ more channels in the front hemisphere than the back. Imaging is also better horizontally than vertically and so good engineering also dictates that channels must first be added in the same plane as our ears before going to higher elevations."

So: "The first level of surround stage enhancement comes from adding the Wide channels. The second level comes from adding the Height channels. If it is practical to have both Wides and Heights then the surround performance will be further enhanced."

Receivers with DSX may come this summer, Audyssey says. As far as we can tell, DSX is a listening mode, as opposed to an encode/decode process, so there will be no width-enhanced software as such. "DSX automatically reconfigures its processing to optimize surround rendering over any number of available speakers beyond 5.1," says the primer.