Just got these in from amazon.jp. Not really sure what to say... they're
fantastic!! Everything I love about that Yamaha sound, clear, fairly neutral, not peaky, but a beautiful sonic quality and fairly transparent. I listened to electronic music all day at work with these, lots of strings and percussion as well. They handle it all with ease. Vocals sound fantastic, what can I say... Tried them on my Fiio E17k and Magni/Modi stack. They sound splendid on both setups, a bit more reserved and warm on the Fiio as usual... Build quality is really nice, they are comfortable and relatively light, very attractive looking headphones and they feel solid as well. I don't really have anything bad to say about these right now. I just recently got a set of Hifiman HE-400i and maybe it's too soon to judge, but if I had to keep one, I'd reach for the Yamahas! Maybe it's because I can use these at work, and the bass is so silky smooth ;-}
OK just tried out some metal... definitely better genre for the HE-400i
but I'm more of an electronic music kinda guy
Diablo 2 soundtrack sounded spectacular on the Yamahas earlier today. Excellent representation of all the crazy string instruments and especially the percussion that Matt Uelmen uses in that soundtrack.
I listen to many electronic music genres, anything from chill to trance, progressive, trap, hardcore, nightcore, chiptunes/8-bit, VGM, future, big beat, club, ambeint, etc, etc...
Overall... I'm
loving these headphones!
EDIT:
I have updated my opinion on these headphones, which somewhat contrasts this post http://www.head-fi.org/t/827438/yamaha-hph-mt8-studio-monitor-headphones/90#post_13409558