Dear HD555/595/598 users...
This headphone generally has a very high driver distortion in loud volumes or with a lot of bass, probably extremely amp picky. (well amp picky isn't an objective observation, getting distorted with a lot of frequency ranges is)
Nevertheless...
This headphone SHINES at low listening volumes. It's the best headphone I have for low listening volumes.
Which makes it also a very healthy headphone for long listening sessions and to fall asleep with.
The tonality is so great and tidy that even extremely complex music sounds amazing and cohesive as if you've put on some TOTL headphones although these headphones usually aren't detail cans.
If you haven't tried it, please try listening to music quietly and see the light!
For calmer music, try Bee Gees, Dire Straits, Kate Bush, classical, jazz, but really anything can work. Even EDM gets a special vibe.
I almost think they are meant to be experienced this way