Digital Loudspeakers: Viable Hi-Fi Technology?

Given that almost all aspects of domestic hi-fi front-end has already gone digital these days – digital radio broadcasts, CDs, DVDs, digital music downloads, etc. Are our hi-fi loudspeakers the next component to go digital?


By: Ringo Bones


Virtually all aspects of hi-fi that’s still commercially viably traded has already gone digital, thanks to the slogan Going Digital and Digital Ready being brandished about for much of the 1990s. As in digital radio broadcasts, digital music downloads, CDs, DVDs, digital preamplifiers, digital power amplifiers, etc. Even analog TV broadcasts in the US has since virtually gone digital back in the middle of 2009. But has anyone recently checked if the humble hi-fi workhorse, namely the ubiquitous hi-fi loudspeaker, has already gone digital?

Back in September 1998, a start-up digital speaker development company called “1…Limited” has then announced a new drive to attract investors and partners (I smell IPO?). The Cambridge-based company at the time aimed to make its innovative technology out of the laboratory and into production – and hopefully into your listening room – within two years. The design concept of 1…Limited was a panel matrix loudspeaker which runs from raw digital code (SPDIF?) without the need for any Digital to Analog Converter (DAC) or power amplifier. Given that our ears – as far as we know at present – are analog and, therefore, a digital speaker must create sound waves in the air by integrating air pressure pulses – from an amplified bitstream from either CD or DVD player into the listening room.

During the past 30 years or so, all major consumer electronic manufacturing firms – Philips, Sony, Panasonic, etc. – have been working on digital speakers, more often than not filing their very own patents to the nearest patent office of their very own versions of the same theme – i.e. digital loudspeakers. And all of them eventually found out first-hand the nasty surprise that’s in store.

Full working details of a digital loudspeaker were already published back in April 1980 – three years before CD was commercially launched by Sony and Philips. The article appeared in the now defunct magazine called Hi-Fi For Pleasure. The author was Stan Curtis – who eventually invented the audiophile CD player in 1985, later became MD of Wharfedale loudspeakers and Chairman of IAG, which owns the hi-fi company Quad. Stan Curtis’ article was spread over two pages and included a block circuit diagram and sketches said to be taken from a patent application filed by a Japanese company.

The system was called DARTS, or Digital Action Reaction Transmission Speaker, and it has been developed by NEBCO, the Osaka-based Nippon Electrical Bearing Company. Before reporting on the demonstration to selected journalists, Curtis reminded everyone that the loudspeaker has been the major stumbling-block to any progress in the digital chain – i.e. a truly all-digital hi-fi system.

NEBCO set up a demonstration using specially produced digital discs replayed on a prototype Sony disc player. According to Stan Curtis, the subjective performance defies description. There was no noise, no distortion, no coloration, wow and flutter or rumble, and apparently unlimited reserves of volume. The result could not be compared to anything heard previously: it was just so real. One particular revealing passage was an atmospheric-sounding street recording. Being reproduced at sensible level, the effect was as though someone had opened a window out on to the street.

NEBCO’s sketches showed a flat panel built from a helix of numerous tiny pistons, selectively triggered by a digital bitstream. For low-level sound, only the central drivers were switched on, to pump a few packet pulses of air. As the pitch and volume or a note rose, more drivers were rapidly triggered. At maximum sound level, all the drivers pumped. The discrete packets of air integrated in the room to create an analogue soundwave. Because each driver was either on or off, there could be no distortion or coloration like that found in a conventional analog speaker.

NEBCO promised a 450-quid bookshelf version, but it never appeared. Those in the know where not surprised because Stan Curtis wrote the article under the pseudonym Olaf Pirol – an anagram of April Fool. For all intents and purposes, DARTS was an elaborate hoax to celebrate the first of April 1980 a.k.a.April Fools Day. When 1998 rolled in, only a few hi-fi industry insiders knew the truth. But Stan Curtis eventually owned up to the elaborate hoax that he created through a trade magazine called Inside Hi-Fi in 1998. A few years later, he still finds hi-fi designers who wonder whatever happened to DARTS.

Unfortunately, most existing patent laws around the world makes no distinction between fact and fiction, a mere blueprint from an actual functioning and working prototype. In short, you can definitely patent a blueprint even if the device portrayed by it doesn’t work in real life. Although Olaf Pirol’s digital speaker article was fiction, it will still block anyone who now tries to patent a similar idea as fact – even if he or she possesses a working prototype.