I can't convey into words how disappointed I was when I first put them on. No amount of reviews read prepared me for their sound. Nothing I've heard before sounds like them. I despised their sound so much, I returned them back in the box 30 seconds after putting them on.
Why? Thy sounded incredibly cheap. There was no layering or separation. Everything sounded like coming from the same aural plane. They also sounded very shouty and thin. This has never happened to me before. Most of the stuff I own sounds good straight from the box and doesn't need "break in".
Anyway, hours later, I took them out the box again and I let varied music play through them at moderate volume for about 8 hours. They started sounding less cheap, but still not good enough for me to keep them. I gave them another 8 hours and they settled, with the soundstage opening up and the instruments sounding layered.
While they remained shouty but to a less extent, they drastically improved in every area. No longer do they sound cheap. Bass knob at 50% yields light but adequate lows. Over 70%, it sounds weighty, but separate from everything else. Midrange is not open, but it's not recessed or pulled back. It's cohesive with everything else. Highs are bright but not piercing.
While their tonality is unnatural and sound signature is weird and an acquired taste, sound quality-wise, these do sound like $500 headphones. NO DOUBT ABOUT THAT. They are detail monsters. I decided they were different enough (and good enough) to keep them.
Also, they're SO sensitive. Nothing else I own sounds so loud at such low volume settings. I have an LG G8, and 25 out of 75 is louder than all my other headphones regardless of impedance or sensitivity. Same on the V35 I had, which has the same ESS Technology audio guts as the newer G8.
Comfort-wise, I don't find them comfy, but I can wear them for hours and my big ears don't hurt and neither my head. They're more on-ears than over-ears, but the ears do get squished inside the pads without being tortured.
If you want a similar sound than the open Sennheiser HD 58X/6XX, look elsewhere. These sound totally different. To me, they sound more like my Denon AH-D340, but way better and funner. Thanks for reading. GOD BLESS!