NHT, DEQX, and PowerPhysics Collaborate
By Kalman Rubinson June 28, 2004 — The NHT Xd DSP powered speaker demo was held at the Plaza Hotel in New York City last week and representatives from NHT and its supporting cast, DEQX and PowerPhysics, opened by explaining the philosophy behind the new product and the essential components they each contributed (also see previous).

First up was NHT's managing director, Chris Byrne, who said that the Xd represents the company's approach to providing a small, domestically acceptable (read: high WAF (wife acceptance factor)) system which would not sound like a small system and which would satisfy critical and serious listeners. The use of DSP and class-D amplification with modern drivers and advanced cabinet construction provides for a system which has wide dynamic range and flat frequency response, and can offer optimized performance without precise placement or room treatment.

Next, Kim Ryrie, CEO of DEQX, explained how the inclusion of that company's DSP capabilities provided extremely high-slope crossovers between tweeter, midrange, and woofer; driver frequency correction for flat response above the bass; and time delays to compensate for the spatial offset between sub and main speakers. (While the system can be enhanced for room equalization, that is not included in this product.) Ryrie emphasized the importance of high-speed processing algorithms and the role of high-slope crossovers (over 100dB/octave!) in improving system radiation and lowering distortion.

PowerPhysics' president, Gordon Wanlass, described how PowerPhysics' switching amps were small in size and high in efficiency, typical of their type. He also explained how their unique circuitry provides high-speed error correction during each switching cycle and, thereby, virtually eliminates distortion due to clipping.

The demo Xd system consisted of a pair of small XdS satellites (1" neodymium-magnet tweeter, 5.25" metal-cone midrange) in a composite molded enclosure with MDF and wood finish, an XdW powered bass module (back-to-back 10" drivers and 500W amp) and an XdA DSP/Amplifier component (DEQX DSP with 24/96 A/D/A, 6 output channels, 4 channels of 100wpc (600w peak) output). The only controls on the XdA permit the user to define the boundary equalization to adjust for each speaker's relationship to room surfaces.

Thus, the Xd system is, in effect, an active speaker system which requires a volume-controlled source, such as a preamp or A/V processor. Fit and finish of the speakers and the electronics was first-rate, and the system can be scaled to include multichannel setups with the sound quality and advantages of the two-channel system.

Performance revealed a sound that was surprisingly balanced and wide-range despite an untreated hotel room with a large mirrored niche between the speakers. Clarity of prepared demo material as well as my own discs was excellent. Bass was fairly deep and well defined.

I was quite impressed with these extraordinarily open and low-distortion small speakers; nonetheless, they did still seem like small speakers. Of course, one cannot avoid knowing they are small, both from the entire spoken presentation and also from simply looking at them. It will take a more extended audition in more familiar surroundings to circumvent this bias, and I hope to review this exciting system very soon.