http://www.stereophile.com/reference/1104red/

more specifically

http://www.stereophile.com/reference...ed/index3.html

"Although the initial fuss that accompanied Ray Kimber's 1999 launch of
DiAural-the proprietary speaker-crossover technology developed by Eric
Alexander-has died down, the fact remains that it was and still is promoted
as a means of canceling the Doppler distortion introduced by microphones:
"Doppler Decoding," in DiAuralspeak. To my knowledge, however, this claim
has never been challenged in the audio press."

"...for a microphone to introduce significant levels of Doppler distortion,
its diaphragm would have to undergo large excursions-of the same order as
the loudspeaker diaphragm, if cancellation is to be feasible. In fact,
microphone diaphragm excursions are minuscule. I asked Stephan Peus,
president of development at Georg Neumann GmbH, to provide me with some
representative figures. He e-mailed back a document, "Some Amazing Facts
with Condenser Microphone Capsules," which quotes the diaphragm excursion
for Neumann's KM 184 microphone (a miniature cardioid) as being just 10
nanometers-that's four-tenths of a millionth of an inch, or about a 40th the
wavelength of blue light-at an SPL of 94dB. Compare this with the 7.5mm peak
excursion required to generate this SPL at 100Hz in free space and at 3m
(10') listening distance, using a drive-unit of 200mm (8") effective
diaphragm diameter. The two figures differ by a factor of 750,000! Depending
on their mechanical characteristics, the diaphragms of other capacitor
microphones may undergo larger excursions, but their displacements will
still be orders of magnitude smaller than a loudspeaker cone's

IOW, when Kimber snowed Stereophile about his abilities to correct Doppler
Distortion in microphones, he was talking trash.

I notice that the origional offending article has been expunged from the
Stereophile web site. It used to be located at
http://www.stereophile.com/shownews.cgi?416 .

Here are quotes from the missing article and my comments about it that were
posted here at that time:

http://groups.google.com/groups?selm...u tput=gplain

-------start long quote that embeds quotes from the Stereophile web article
that now seems to have gone missing

http://www.stereophile.com/shownews.cgi?416 says:

"Five weeks ago we reported that Ray Kimber, of Kimber Kable fame, and his
financial partner, Bruce Bastion, were in the process of bringing a new
loudspeaker technology to market. DiAural, as they've named the technique,
is claimed to eliminate what Kimber calls Doppler-encoding distortion---the
modulation of high frequencies by low frequencies of higher amplitude."

This roughly corresponds to the classic understanding of Doppler
distortion.

W/R/T classical understandings of how to reduce FM distortion in speakers,
this article seems to make some false claims, such as

"According to Kimber, this encoding takes place in the microphone, survives
intact throughout the recording and playback chain, and, if left undecoded,
seriously detracts from any audio system's verisimilitude."

Actually, Doppler distortion is due to velocity and changes in velocity.
Speakers like the Bose 901 are specially exposed to it because their
woofers and tweeters are the same driver. When the speaker's cones travel
at high velocities to produce bass, treble is FM modulated by the Doppler
effect. If treble is reproduced by a different cone, or if the speaker cone
is prevented from attaining a high velocity, then doppler is greatly
reduced. Thus, the classic two-way speaker system has greater resistance to
Doppler distortion than a single-way. Also, this means that one of the
benefits of having a subwoofer is reduced Doppler distortion.

As a rule, microphone diaphragms don't move fast enough to cause doppler
distortion. Ever see a microphone diaphragm stroke like a small woofer
being driven with heavy bass? Nope - most mics would be physically damaged
if they tried to do that! Therefore, the "coding" mentioned here is
unlikely to happen.

"The DiAural technique, developed by designer Eric Alexander, performs
decoding at the speakers themselves, using a couple of common parts
configured in a novel way that enables a woofer and tweeter (or woofer,
midrange, and tweeter) to "talk back" to each other, freeing them to
jointly produce sounds more like those that originally impinged on the
microphone."

Sounds like low slope crossovers or some other technique that reduces the
isolation betwen the drivers. This is old news, and generally found to be
the exactly wrong thing to do if the goal is to minimize Doppler
distortion.

"The DiAural circuit replaces the traditional crossover network, which
means the drivers are connected directly to the amplifier. All of which
made for an interesting telephone discussion I had with Kimber before
writing this story."

If the speakers are "connected directly to the amplifier", then there is no
crossover network. This is actually the worst case for creating Doppler
distortion.


-------end long quote that embeded quotes from the Stereophile web article
that now seems to have gone missing