The B&W DM-6 is the second "phase-coherent" speaker system we have tested. (The first was the Dahlquist DQ-10
in January 1977.) From what we see in the latest ads from the US, England, and Japan, there will be more forthcoming. One speaker manufacturer who has been around for a long time and is currently pushing his own "phased" systems observed that many of his competitors' designs are being introduced merely because "phase response" sells these days. Yet the truth of the matter is that the experts still do not agree as to whether linear phase has any effect on reproduced sound.
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.