DSP Based Digital Loudspeakers: Caveat Emptor?

With the vinyl LP revival still incrementally on the rise since the 1990s, are DSP based digital loudspeakers still represent a good buy?

By: Ringo Bones

The favorable review of the DEQX PreMate – a DAC, preamp, room correction and speaker correction all in one box - by Stereophile magazine back in December 2014 had got me thinking and checking out new DSP based digital loudspeaker systems even though my chances of ditching my current system and going “all digital” is just about zero. But given that I’ve heard one being demoed in Hong Kong recently, I wonder if DSP based digital loudspeaker systems, like the one which the DEQX PreMate can be used to retrofit any analog based system given it provided wonderful results with even an analog LP input and it can also handle 24-bit 192-KHz PCM digital / DVD audio and even SACD – that DSP based digital loudspeaker systems has finally come of age? 

The first time that I got the time and money to go shopping and buy a serious high-end audio kit was during the early 1990s. At that time, vinyl LP playback and vacuum tube amplifiers – especially single-ended triodes – where the proverbial bees knees. Back then, I had the good fortune to closely audition a number of DSP based digital loudspeaker systems that offered digital domain equalization and room correction abilities –although not long enough to make me conclude that they are better than an all-analogue system built around vinyl playback. 

One of these was the DGX Audio’s Digital Deconvolution Audio System consisting of the DDA-1 Digital Deconvolution Power Amplifier and the DDL-1A Loudspeakers. It was sold part-exchange to a hi-fi shop I frequent in my end of the woods back in 1995 as the owner upgraded it to a single-ended triode based system. The DGX Audio’s Digital Deconvolution Audio System, to my ears at least, managed to sound like one of those powerful single-ended triode vacuum tube amps employing Nobu Shishito type inverted interstage transformers but it was limited to playing back Redbook spec 16-bit 44.1-KHz sampled PCM material, which I think the owner, sold it because of the impending 24-Bit 92-KHz DVD Audio which was slowly creeping in during that time and it did sound better than CD.  And until this day, the DGX Audio Digital Deconvolution Audio System unit still remains unsold in that particular hi-fi shop despite of the oohs and ahs of everyone who heard it being played.     

During the mid to late 1990s, I was really tempted to buy a “digital equalizer” in the guise of the Z-Systems’ RDP-1 Reference Digital Preamplifier, which is an all digital preamp with tone controls. Despite some favorable reviews and the product did managed to generate a good impression on me after hearing one being demoed in a local hi-fi convention, at the time, I just thought that my system really needed one given that it was already sounding okay to my ears at least and it priced at 5,000 US dollars each at the time (I wonder how much these units are going today second-hand?). And inexplicably until this day, I’ve never heard or read in hi-fi magazine reviews of the Z-Systems RDP-1 being compared to an all vacuum tube based preamplifier. 

Another DSP based digital speaker I had the good fortune of hearing first hand was the Quadrature Model DSP 5 Loudspeaker. Dubbed as the first American DSP based digital loudspeaker back in 1996 because at that time, the only other high-end audio manufacturing firm making one was the UK based Meridian. The Quadrature Model DSP 5 offered digital domain time domain and phase correction that easily made its soundstage presentation more natural than ordinary similar sized loudspeakers on the market at that time and not to mention a midrange creaminess that’s comparable with single-ended triode vacuum tube amplifiers sporting over-sized output transformers. Inexplicably, nobody mentions this product anymore this day and age. Despite of its already long history of relative success, are DSP based digital loudspeaker systems really a good buy or should we exercise “caveat emptor”? 

Jeff Joseph of Joseph Audio commented on the March 1998 issue of Stereophile magazine that: “Digital is still revolving at a rapid pace, with little real consensus in sight. Buying digital speakers involves a significant investment, with the risk that such technology will be rendered obsolete in the coming year. The highway to high-end heaven is littered with yesterday’s state-of-the-art digital products at fire-sale prices.” Fast forward 17 years later and Jeff Joseph’s nugget of wisdom at the time still holds true, some hi-fi stores even have some DSP based digital loudspeaker systems that still remain unsold when they bought them back in 1995 because prospective buyers of such products, despite being wholly impressed, immediately backed out after learning that such products an only “play” 16-Bit 44.1-KHz sampled CDs or Redbook spec CDs despite such products being offered at one-tenth its original price when it was still new back in the early to mid 1990s! Are newer systems that offer room corrections but offer full compatibility – i.e. to analog vinyl and Super Audio CD playback – a better buy for the first time audiophile?