Also, mass:
Lighter material = more high end extension, higher resonant mode frequency, less dependence on spider dampening
Heavier material = less high end extension, lower resonant mode frequency, more dependence on spider dampening
Here's the reason 'stats have great high end extension and why balanced armatures have high resonant frequency.
(BAs don't have the extension, because they're highly dampened - otherwise they'd ring like hell.)
For example, mylar is a comparably heavy, stiff material, while cellulose is very light and flexible. Most microfibres are inbetween.
Carbon nanotubes are an interesting rare material, stiff and pretty light. Metal film is comparable to mylar, but usually slightly lighter.
