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Flat-panel speakers utilize roughly the same technology as their more familiar conical cousins, with one fundamental difference: flat-panel speakers thrive on chaos and interacting sound waves.
Flat speakers can amplify sound with panels that may be only millimeters thick. The best-known versions of flat-panel speakers rely on technology introduced four years ago by the British company NXT. In a typical speaker, an "exciter," a magnet-and-coil device about the size of a dollar, translates electrical impulses into tiny vibrations. From the point where the magnet assembly is attached, ripples of sound 10 to 15 microns in amplitude radiate across the panel, hit the edge and travel back, until the entire surface of the panel vibrates. Because the waves are so small and similar, they do not interfere noticeably with one another, according to NXT's Adrian Horne.
The resulting sound waves broadcast uniformly in 360 degrees, with the panel at the center. The sound seems undirected, in contrast to that coming from cone speakers, which tend to "beam" sound toward one ideal location. "The center of a cone is driven farther and faster than the outside is," explains Olin D. Williford, a sound engineer for Benwin Sound, a subsidiary of Kwong Quest in City of Industry, Calif. (one of the 205 companies to which NXT licenses its technology). "Pushing the air in different waves from the center to the outside gives higher frequencies at the center than at the edge, so the dispersion of sound narrows." Flat-panel speakers distribute all frequencies equally, from both surfaces. One suggested use of the panels' so-called bipolarity is for public-address systems, with both sides broadcasting sound.
This article was originally published with the title The Well-Rounded Flat Speaker.