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 December 15, 2005 Banishing Speakers Maybe it’s some sort of backlash against all those surround-sound speakers cluttering up your home theater, but it seems there’s an increasing trend to reduce the number of boxes without sacrificing sound quality.One bit of newspaper advice I read recently said, without qualification, that you could simply forget about a center speaker. And an ad for a respected speaker manufacturer (whose engineers should have known better, or at least ridden herd on the ad-copy writers) said that the "extraordinary dispersion characteristics" of their front-speaker pair "means that you can enjoy crystal clear imaging without the need for a center speaker." Both are just wrong. Imaging -- the illusion of hearing a center channel when there isn’t a center speaker to reproduce it -- was always a compromise in conventional two-channel stereo. Ever since the 1930s, acousticians have known that three channels is a bare minimum, because you can be fooled into thinking something is in the middle only if you’re exactly equidistant from both speakers. If there is actually a speaker in the middle, sound will seem to come from there wherever you sit in the room -- because sound really is coming from the center. Even so, there does seem to be a strong desire to reduce the number of speakers, and several manufacturers have begun using sophisticated psychoacoustic algorithms (see "Playing Audio Mind Games," September 2005) to re-create surround effects from a minimum of devices. I awoke the other night, after dozing off during The Letterman Show, to see an infomercial from Bose for their 3.2.1 system, which uses a miniature speaker on each side of the screen, plus a subwoofer, to do the full 5.1-channel job. Polk Audio has its SurroundBar, which purports to do the same thing. (It might well have an actual center driver in the box -- hard to tell from the ads.) As I mentioned in my September column, this technology can be startlingly convincing, and I have no doubt that its appeal will be such that more companies will jump on the bandwagon. But it suffers from the same drawback as two-channel imaging: its success depends on where a listener sits in relation to the speakers. Still, I’m sure there are many listeners willing to put up with such limitations to reduce the clutter in their home theaters. ...Ian G. Masters
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