Red Shift: Doppler distortion in loudspeakers Keith Howard returns to DiAural
When I wrote the "Doppler and DiAural" sidebar for my recent feature about Doppler distortion in loudspeakers ("Red Shift," November 2004, p.67), I fully expected a retort from DiAural founder Ray Kimber, of Kimber Kable. In the event, both he and Eric Alexander, the originator of DiAural's crossover design concept, took up their pens to point out to me that the Doppler decoding explanation with which DiAural was launched had been withdrawn before my article was published.
I wish, of course, that I had known this before writing "Doppler and DiAural," although it would not have dissuaded me from including the sidebar or much altered its content. A thorough explanation of why a loudspeaker cannot cancel out the Doppler distortion generated by a microphone (and vice versa) is just as valid now as it was before DiAural's retraction.
In my correspondence with Ray Kimber, I pointed out that one reason I (and, surely, countless others) believed the Doppler decoding explanation was still current was the continued citation—and, in one case, linking on DiAural's website—of press articles repeating the Doppler claim, without any cautionary note to the effect that it had since been rescinded. Promptly and, I thought, in a very gentlemanly way, Kimber conceded this point and immediately set in train changes to the website that will prevent it from, in the future, promulgating this discredited explanation of DiAural's sonic effect. (Which, as I won't need to remind Stereophile readers of long standing, earned the launch of DiAural enthusiastic column-inches in much of the audio media.)
Eric Alexander has assured me that he has never developed a crossover topology that was intended to eliminate Doppler artifacts, which reinforces my observation in "Doppler and DiAural" that DiAural's two patents, which cite Alexander as the inventor, make no mention of Doppler distortion in their texts. Doppler decoding, it seems, was merely an attempt to explain the sonic benefits of DiAural, and so came after the event, not before.—Keith Howard