An extra 1 million pounds of funding secured last week by four-year-old Cambridge, UK company 1…Limited, should be enough to see the developer of the world’s first digital loudspeaker through its last stage of pre-market development. Dr. Tony Hooley, the company’s founder, said it had recently signed an agreement with a major loudspeaker manufacturer which should be turned into 1…Limited’s first license deal shortly. We will be very disappointed if we do not receive our first revenues before the end of next year, Hooley said.
1…Limited’s digital technology is set to drive the first fundamental change in sound production technology since the loudspeaker was invented in 1925. Since then, said Hooley, loudspeaker manufacture and development has largely been a matter of woodworking. Now though, using a combination of advanced digital signal processing, acoustics, and ceramic materials technology, Hooley claims to have invented a means of excluding all analog signals from audio systems, producing a more power efficient, higher quality means of generating sound.
Conventional loudspeakers use magnetic motors to replicate an analog electrical signal as an air pressure wave by vibrating the membrane of a speaker housed in an acoustic box. It is an extremely power inefficient means of producing sound, consuming 100 Watts of power for every 1 Watt of output, and even the best conventional speakers introduce increasing sound distortion as the power to drive them rises – typically as much as 10% distortion, according to Hooley. 1…Limited’s technology is so efficient it will produce powerful audio output using 10s of milli-Newtons of [physical] power, compatible with the electrical power needed to drive a CMOS processor, while producing as little as 0.005% distortion.
To achieve this breakthrough, 1…Limited has worked with a number of partners to drive advances in three key areas of development. Two of these, digital signal processing technology and ceramic material design and manufacture, have come together to produce the large arrays of very small transducers with which 1…Limited replaces the one, or sometimes two or three larger transducers that are found in most conventional loudspeakers.
These very small transducers use ceramic motors (which do will not interfere with a computer screen as a conventional magnetic motor will) made from thin polymer layers created by another Cambridge company, Ranier, to encase tiny ceramic pistons developed in conjunction with the University of Birmingham, and a Dutch manufacturer. According to Hooley, the mechanical amplification characteristics of these transducers is similar to that produced by lightly squeezing a wet bar of soap in your fist – a tiny radial movement produces a strong lateral movement in the bar of soap, as it shoots across the bathroom. In audio terms, this converts into a loud output, from relatively small power input.
The sound produced by large arrays of 1…Limited’s transducers is also qualitatively different from the sound produced by conventional speakers. The company presently has a 256-transducer array (which could be magnified to a 1024 array for a more powerful system, or reduced to 32 for a cheaper, more compact speaker) which allows each transducer to be addressed by a different digital signal channel. Each channel can be programmed to produce a slightly different effect, which can be exploited by the digital loudspeaker systems in different ways. The signals to all 256 transducers could be used to spread sound evenly across a large area, or some transducer could be used to point sound at a different location, or locations.
In a public address system, for instance, a digital loudspeaker could be used to point sound only at that part of train station platform where passengers are actually standing waiting for a train. And the volume of the sound could be controlled to ensure that it does not interfere with the same message received fractionally earlier or later by another group of passengers standing closer to another speaker on a different part of the platform.
And an even cleverer trick made possible by a digital loudspeaker is to use psychoacoustics to spoof a listener into believing a sound is coming from a direction where there isn’t actually a speaker. Psychoacoustics is the science of how people hear sounds, and how the acoustic effect of the shape of our heads distorts sound in ways which we intuitively interpret to locate where a sound is coming from. The rich variations of sound that a large array of transducers produces could allow audio systems to produce noises which sound as if they are coming from behind, beside or underneath a listener, even though they are actually sitting directly in front of the speaker. Quite how frightening, or thrilling this technology could be embedded in a device such as Game Boy remains to be seen.
And digital loudspeakers ought to be small enough and power efficient enough to be embedded in things like the Game Boy. Hooley says 1…Limited’s third major development strand, in acoustics, has produced a material in conjunction with the University of Paris and a German manufacturer which absorbs unwanted sound. In a conventional speaker unwanted sound usually means the low-frequency bass sounds which leave the back of the speaker in antiphase to the same sounds leaving at the front. Unfortunately, to the human ear these sounds appear to arrive at the same time, and cancel each other out, so a conventional speaker has a deep back which seeks to muffle the unwanted antiphase sound. With the new absorbent acoustic material developed by 1…Limited speakers can be flatter, says Hooley.
Quite what devices 1…Limited’s digital loudspeakers may end up in remains to be seen, but since they dispense with the need for any kind of digital to analog conversion, their direct connection (either by wire, or by a wireless method that the company is also working on) to any kind of digital radio, CD player, computer or games console, should be both easier and cheaper than connecting an analog speaker.
Within three to six months, says Hooley, the company’s major loudspeaker manufacturer customer plans to bring the first commercial version of 1…Limited’s technology to market as a high end Hi Fi speaker. But audio system makers are unlikely to be the only companies showing an interest.
