A couple of years ago Sydney-based Lake Technology developed audio processing algorithms and hardware to make headphones sound like they’re producing surround sound. The success of this enterprise is attested to by the fact it was was duly licensed by Dolby Laboratories as Dolby Headphone.
Now another Sydney-based company, DEQX, has come up with a SHARC DSP-based digital processor (the PDC-2.6) to pre-process stereo audio signals to counteract deficiences in loudspeakers. This does four different things:
- equalises the speakers for frequency response and phase uniformity across the audio band
- eliminates phase discrepancies between the drivers in a two way or three way loudspeaker
- provides extremely steep crossovers between the drivers, free of phase shift
- equalises the in-room bass response of loudspeakers
All this is done in the digital domain. Of course, it works at line level, with 96kHz/24 bit analogue to digital converters and 192kHz/24 bit digital to analogue. Or you can feed a PCM signal directly into it to skip the first A/D conversion.
The DSPs that do all the heavy EQ and phase manipulation and crossing over work with 32 bits of resolution. You can either have the unit set up for you by installers, or get the calibration kit which includes Windows 2000/XP software and a calibration microphone.
The reviews quoted on the company’s Web site are extremely positive, and the whole concept is very appealing to me. Those speaker makers committed to the highest quality have to go to herioc lengths to reconcile the often contradictory demands in crossover design: smooth frequency response, minimal phase distortion, steep filter slopes, even impedance across the audio spectrum. One or more of these goals always suffers.
Where did the expertise for all this come from? Today I had a chat on the phone to DEQX CEO Kim Ryrie. Turns out that he was also the man behind the famed Fairlight Computer Musical Instrument back in the mid-70s.
It’s also worth noting that the DEQX system (previously known as ClarityEQ) has been installed in such recording studios as Abbey Road.
Basic prices start at somewhere in the $AUS4,000 to $5,000 region. Precalibration for rooms on supplied detailed specification, using acoustic modelling, comes to around $US900. But you can make do with the internal parametric equaliser to make the necessary adjustments if you like.
This is not for no reason. Apparently most music purchasers want their CDs to be loud. If they are listening to a set of CDs on a CD jukebox, when one that comes up that seems less loud than its predecessor, they are disappointed. Perceived loudness is a function of average playback level, not peak level.