JVC HA-FXD80 as other IEMs as well, depend a lot on the source and amp that drives it.
Today I tested it with Fiio X3 + Fiio E12DIY with Muses02 Op-Amp and LME49600 buffer.
The tonal balance of FXD80 changed a lot, the mids now thick and full, and the treble a bit dark (darker than what I use to hear). It changes from natural V shape tonal balance I use to hear with iPod, mobile phone, and Fiio X3 headphone output, into natural thick and full body midrange with rather dark treble... I was very surprised
So, try with other player and amp, the tonal balance might changes a lot
i definitely agree i tried running them straight off my iphone then i attached me fiio e6 amp to it
definately the amp makes a difference
small but i notice it but with the equipment i have and listening to this is probably it for me (use my macbook pro no dac, iphone 4, ipodtouch with fiioe6 amp)
even after the a/bing the mids are still recessed the fiio e6 makes its darker more midbass and lower to middle mids so it helped a bit for male vocals gave it some authority and thickness but nothing major, i had to listen very closely to pick it out
if anything it lost some the treble (its a toss up whether this is good or bad, i actually found the fxd/r 80 a bit bright for me off the iphone so the fact the amp tones this down was nice ) but there was a loss of sparkle =( can't have it all i suppose
female vocals still sound relatively the same
but in terms of speed the fxd80 for the amount of bass is has its defintely faster than my monster turbines