So I have been testing the JVC HA-FX40, not completed the burn in yet, about 15 hours so far. And for the burn in I have been listening to them for most of the part. First thing that came into feeling was the excess sibilance when i put them on first time, listening to some old Iron Maiden (Killers). I was turned off, but reading here it is a common problem, today they sound actually a lot better. It is a very nice sounding headphones. Much better than many cheapos out there for sure, and classes ahead of Senn 300 cx. Why am I mentioning 300cx? Well it was collecting dust and I brought it to work, now I know why it is collecting dust. Wow how the industry progressed over the years.
I don't have that bassy feeling with the FX40, it is very balanced and imo a bit more towards mids and treble, still has the annoyance on highs when you hear just human voice without any music etc (just happened on spotify commercial), but I hope it will cure itself with more burn. So far I am liking this very much for rock, metal etc. The instrument separation is working wonderfully, guitars are coming alive, needs a bit more of that drum kick punch, bass lines are wonderful, vocals are great and clear. It is like Grado SR80i's iem version.