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
IMO they're amp picky mostly in that they have highly variable impedance together with a fairly low nominal impedance, so any amp with higher than 5 ohm output impedance can cause bass bloat which is really bad on the HD598 'cause their bass is very prone to boominess as it is.
Nice sounding at lower volumes, yeah they're definitely nice no argument from me there, but imo outclassed these days by other options such as the 560S or 58x.