It's not an assemblage of carbon dust, it's an actual grown layer (true bi-cubic/tetrahedral arrangement of pure carbon atoms). The substrate is 45 microns, and it is quite flexible (it's a custom/proprietary ultra-high temperature thermopolymer). It's a little stiffer than the beryllium foil, but due to the heavier mass (carbon is quite a bit heavier than beryllium), has about the same natural resonance. Of course, in the small IEM body, the resonant frequrency is pushed really high (above 2 kHz), so we're in the pure piston-motion/spring-mass dominated portion of operation.
Here is a good primer on how diamonds are grown. Our process operates at a lower temperature, higher pressure (thanks to the smaller pressure chamber we can run higher PSI without concern), and for a longer time per unit thickness (typical growth rate are around 1mm/week, we're around 15% of that rate).
