Meridian DSP8000 digital active loudspeaker
The idea of integrating the power amplifier into the loudspeaker was not new in the pro audio world even then—in my days as a musician in the 1970s, I had become used to seeing powered Spendors in TV and radio studios. Yet in the world of high-end audio, Meridian has done more than any other company to establish the concept.
Yes, I know—British cohorts Linn and Naim have always offered active versions of their speakers, but these still use external amplifiers and line-level crossovers. Meridian's approach of fully integrating the design of the speaker with that of the amplifier and control circuitry is currently echoed only by Canadian company Paradigm and companies serving the studio market, such as Genelec and Mackie.
And in Meridian's D600, which I reviewed in the November 1989 Stereophile, the concept was extended to include the D/A processors. Such "digital active" speakers both keep the music data in the robust digital domain for as long as possible, and allow the usual analog functions of volume adjustment, equalization, and crossover filters all to be realized with digital signal processing (DSP) chips. All you needed to complete a music system using a pair of D600s was a digital source, such as a CD transport.
Enter the '8000
The Meridian DSP8000 is the culmination of those years of work by Meridian's Bob Stuart and his team. Standing more than 4' high, the '8000 is a truncated pyramid carrying the tweeter and midrange unit sitting atop a gently curved bass bin containing no fewer than six 8" woofers. Three of these plastic-cone, long-throw units are mounted vertically in-line on each side panel, thus reducing vibrational excitation of the enclosure.
The HF unit's voice-coil is silver, and its dome is specified as being formed from a "composite" material, which I assume is an aluminum alloy modified with a surface treatment to increase its stiffness. The dome is surrounded by a short, conical flare and protected with black wire mesh. The midrange unit's transparent cone is fabricated from "a uniquely light and stiff combination of polymers," and there is a stationary "phase plug" instead of a dustcap.
The sealed head assembly is fabricated from curved pressure-laminated plywood, with layers of wood and steel providing both stiffness and damping. The minimal baffle area offered by the narrow-tapered shape is intended to optimize dispersion across a wide listening area. The head unit is supported on the woofer enclosure by three machined feet, with a flying lead terminated in a four-pin XLR providing electrical connection.
The extensively braced bass cabinet is also constructed from panels laminated from wood and steel sheet, and is finished in high-gloss black piano lacquer. Looking at the speaker from the front, all you see is its 6mm-thick black glass panel, this incorporating a window at the top for the dot-matrix LED display and remote-control sensor. The three machined disc feet supporting the speaker can be converted into spikes.
Inside the '8000
The heart of the DSP8000 is its digital circuitry. The rear panel carries two RCA jacks for S/PDIF-formatted datastreams. These handle data with sample rates of up to 96kHz, as well as Meridian's proprietary MHR encrypted format, and each can be assigned one of 12 alphanumeric labels. After reclocking to minimize jitter, the digital data are sent to two Motorola 56366 DSP ICs running at 100MHz, which perform the following functions:
• splitting the frequency band into bass, midrange, and treble ranges, to drive the appropriate units after D/A conversion
• adjusting the time alignment of the treble and midrange signals, to tilt the listening axis up or down from the tweeter axis
• adjustment of the bass and treble frequency responses
• providing volume control to 48-bit precision
• digital protection against high-level low-frequency transients