New Digital Loudspeaker Technology Announced from England
According to a story in the July 27th EE Times, Hooley believes that his group is the first to demonstrate "proof-of-principle" for a completely digital loudspeaker (see related article). Hooley's new company, 1 . . . Ltd. (one limited), has named their approach the DLS (digital loudspeaker), which they hope to bring to market in two years. Working prototypes are expected by October, with a final transducer design expected by next year.
The article states that "the technology is based on an array of small transducers, each driven independently by a datastream at rates well above audio frequencies. The sound arises out of the additive effect of many transducers, just as a display image is built up by viewing many pixels from a distance. Hooley has calculated that 256 transducers mounted in a panel 12 inches on a side are sufficient to cover the audio spectrum."
"A standard loudspeaker is about 1% efficient," said Hooley, "and audio power amplifiers are 30 to 80% efficient, depending on the configuration. That gives about half a percent efficiency for the total chain. We reckon on 5% to 10% efficiency for the transducers. Pulse amplifiers are 90% efficient, so we could get close to 10% efficiency, or 20 times that of analog systems."
The DLS approach is also based on complex digital signal processing, deploying a binary-to-unary conversion technique that Hooley feels will solve many of the problems associated with using a binary signal. "We're trading complex, almost impossible-to-solve mechanical problems in an analog speaker for complex problems that can be solved with DSP," he said.
Hooley explains that "digital loudspeakers have been discussed in principle for over 10 years, but usually under the assumption of binary encoding." The DLS will use 256-level unary resolution, which Hooley claims is the equivalent of 8-bit binary resolution and can be processed to reproduce 16-bit CD-quality audio.
The company is currently using transducers taken from smoke-alarm detectors, but, along with several other research groups, is developing its own unary-driven piston-like design that it hopes will deliver efficient, high-end sound. Stay tuned.