AFAICT 3580 and 3590 have the same response. Here's a by-ear comparison of the 3580 and 3680 response:
Red: SHE3580, black: SHE3680. I wouldn't read much into the difference at the two ends of the spectrum as the results there are not consistent with different fit from different sessions (for the subbass) and I can't even hear the highest notes; all I would say is that the 3680 has more midbass and doesn't have the 3kHz hump. The other two peaks at 5300Hz and 8000Hz are dependent on tips and fit (I used the small stock tips in both cases, I've sinced moved on to medium tips on the 3580). Remember also that these FR are relative to my own ideal, not an objective flat response.
Thanks for the graph.
So what would you say has a "better sound": SHE358x or 368x? Can you hear any real difference?
Thank you. :)