• Amorphous metals

Somebody's thought about it in a general way- can't be too far off
base an idea.

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S. Chen and R. E. White, "A Mathematical Model for the
Electrodeposition of Amorphous Alloys on a Rotating Disk Electrode,"
Proceedings of the Symposium on Electro-deposition Technology: Theory
and Practice, L. T. Romankiw and D. R. Turner, Eds., The
Electrochemical Society, Inc., Pennington, NJ, 1987

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And, conceptually at least, the subject has be broached [those
diamond diaphragm tweeters are another example I guess]

Sony MDR-V900 Studio Monitor Stereo Headphones

Frequency response: 5 - 30000 Hz
Designed and engineered for most high end applications.
Circum-Aural ear cup design.
Larger, Aura-Nomic design 50-mm driver unit.
Powerful neodymium magnets.
Oxygen-free copper voice coil.
****Amorphous diamond evaporated diaphragm.****
Folding design; case supplied.
Reversible ear cups for single-side monitoring.
Cushioned headband.
Concealed, single-sided LC-OFC Class 1 coiled cord.
Gold-plated stereo Unimatch Plug.
Cord length 9.8'.
3000 mW super high power handling capacity.
10.6 oz without cord.

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An experiment that seems to say you could make planar-magnetic
speakers with amorphous materials

The 1994 IEEE Workshop on Micro-Electro-Mechanical
Systems
Oiso, Japan, 25-28 Jan 94

In one paper, T. Honda of Tohoku University proposed
the use of magnetostrictive materials for
microactuators which are driven by electromagnetic
force in order to achieve the large deflection in
cantilever actuator motion. The paper showed that when
the thin film is fabricated with Amorphous-Tb-Fe or Sm-
Fe, cantilever actuators exhibited the large deflection
under low magnetic fields, indicating the evidence of
achieving large enough electromagnetic force which may
increase the future consideration of using the
electromagnetic force for micro-machine applications.

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I wonder if there would be any advantages using a very thin sheet for a compression driver diaphragm. Then again, it's not just the material that would need to be experimented with, but also the shape of the diaphragm. I think there would still be breakup modes in the audio range, so it would be a matter of tuning them. That would mean material and shape would both come into play.

It would be interesting to check into.