I just got me a pair of Hifiman HE500, and coming from a pair of modified t50rp's my first impressions are the treble's a little shrill, and somewhat overpowers the rest of the frequency range, actually it's pretty annoying, will this change after burn in? But I have to say on a good note, the bass is really well textured; well layered is a better word. I would praise the mids, if it weren't for the shrillness of the treble. I could say the treble's a little too sparkly; a dip at 5000-6000 hz decreases the intimacy of the treble making the vocals sound very smooth and very unaggressive, and a peak at 10k boost overall resolution but makes everything sound thin and grainy.I guess Fang Bian was trying to aim for a more resolute and natural sound; and it would've succeeded if not for the the major boost at 10K. Please tell these cans get smoother with burn in, I've got about 20 hours on them so far.
Oh they definitely get better with either burn-in or brain-burn-in, whichever it is. But definitely mention the amp you're using, as shrill highs are generally noted with inadequate amping AFAIK