[Alzi]

Foster has two bio-cellulose drivers as far as I can tell.

The 40mm neodymium magnet driver with composite bio-cellulose diaphragm in:
CAL!, Denon 1001, Emu walnut

The 50mm neodymium magnet driver with composite bio-cellulose diaphragm in:
Denon AH-D5000, Fostex TH610, TH900. THX00 and in Emu-Teak.

I always see comparisons between the same 50mm or 40mm driver but I was wondering what is the main difference in sound clarity and quality between these two drivers. The price is 10x as much, but is there actually a big difference in the quality? I cannot find any reviews or comparisons but I'm hopeful some of you have heard both.

 

[obobskivich]

I've heard a lot of the headphones you mention here - yes there's a big difference in quality/fidelity (to my ears), with the 50mm-based examples always being superior (as in, IMO/E the AH-D2000, D5000, TH-900, etc sound much better than the CAL!, D1000, etc). I'd also add that you can not, and should not, try to conflate them all into one "bag" - the TH-900 are different animals than the Denon AH-D, just like the CAL! and Denon 1xxx are not exactly identical either. There's lots of variables at play here, and driver dimensions on their own don't tell you enough to make any meaningful generalizations or draw any reasonable conclusions about performance. This can't be neatly reduced to some binary/linear relationship.