there are oblique cones on the market, even more advanced in geometrically addressing break-up problems than ellipticals, and even some "hi-end" "state-of-the-art" units (at least as it is claimed), discussed in separate thread: http://www.diyaudio.com/forums/multi-way/134641-oblique-cone-pros-cons.html
but more to the point of this thread, which is about asymmetrical treatments that lead to a differential wave impedance in a loudspeaker cone, recently I have been searching for good wide-range miniature speakers and some models from TB offered at partsexpress caught my attention, google for: "flower petal" tang band
they seem to employ a kind of asymmetrical treatment of PP or Alu membranes, but unlike Hegeman modifications of Lowthers which were in three parts pattern here a five parts pattern is used
certainly their intention at TB was to introduce a differential wave impedance into the membranes
I wonder whether any measurements were done by Tang Band, or independently, of real effects of this kind of treatment
An externally hosted image should be here but it was not working when we last tested it.
I recall "fixing" a couple of 12" woofers from an Audio Amateur article. One thing was a coating of Varathane (brand for something-or-orher, probably polyurethane). I don't know if it helped the strength, but it really messed with the frequency response. The originals had a rather smooth response up to 2kHz (just listening, as well as looking at a microphone output on a meter), but afterward it had a lot of obvious resonances starting around 500Hz.
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