B&W DM-6 loudspeaker
The DM-6 is an expensively made product using three drivers specially designed for it. The woofer cone is of Bextrene plastic, common in England but rare in the US. The midrange unit is a 6" cone of DuPont aromatic polyamide, "Kevlar," which is claimed to have extremely high internal damping. (This is the first acoustical use of this material that we know of.) The tweeter is a ¾" dome. The cabinet is of complex construction, heavily braced and lined with bituminous felt, which can significantly reduce cabinet resonances.
Sonically, this is not a system to use with tubed electronics. With the best of the tubed power ampsthe Audio Research D-150the system had a rather loose and ill-defined low end, subtle but audible middle-range colorations (including a somewhat distant perspective), and an excessively soft high end. With good solid-state electronics, most of those problems vanished, although the mid-bass range (with the systems well away from room boundaries) was still judged to be overly heavy. Fortunately, there is a bass "contour" control at the back of each speaker (midrange and treble controls are conspicuously placed at the front), and with this set for reduced low end, bass performance was generally excellent but for the typical British rolloff toward the extreme bottom.
Response was subjectively flat to around 45Hz, and weak but usable to a bit below 40. Middle-range coloration was minimal, having no detectable vowel-like anomalies but still a slight tendency to back sounds off a bit from the listener. Highs were very smooth and silky, with an almost-electrostatic-type airiness. Most remarkable, though, was their definitiona quality of razor- sharp focus and delineation of inner details, yet without the irritating bite of most other systems that are comparable in detail.
Driver integration was very good except for a perceptible discontinuity between the woofer and middle range which sounded more like a difference in quickness of attack than a mismating of crossovers. Stereo imaging was very good although not as good as we have heard, which came as a surprise because precise imaging is one thing we had fully expected to hear from a linear-phase design.
The system is not very sensitive, and does best with powerful solid-state amplifiers. A power of 50 watts per side would be minimal, 100Wpc would be better, and more could only improve matters. With adequate power, though, the DM-6s can put out plenty of clean signal, and they are carefully fused against the possibility of disasters.
Like increasing numbers of other speakers, the DM-6s are not designed for placement near room corners or against the rear walls, but well out in the room, and the enclosures are already raised about 8" from the floor on their own, rather oddly-shaped legs. In fact, the appearance of the DM-6 may be its major liability in the eyes of some beholders, because its bay-window front contouring and hind-leg-shaped feet suggest something distinctly animate. The apellation "pregnant robot" has in fact suggested itself to a number of people independently, and it has been the subject of several cartoons in the English high-fidelity press.
Except for the tapering low end, and the tendency toward mid-bass heaviness when the contour control isn't chopping lows, this would have fit nicely in the lower group of speakers rated Class A. As it stands, it is in the upper Bs, although its pristine clarity may not appeal to listeners who like their reproduced sound rich and a bit on the "fat" side.
Does "coherent phase" improve sound? On the basis of these, and the Dahlquists, we would conclude that it does.Allen Edelstein
Mr. Edelstein's report, like those by Ye Ed., represents a consensus of about five people who sit in, at different times, on listening sessions in JGH's home, and who borrow the portable items for use in their own homes.J. Gordon Holt