Mild u-shape. Rather than going the XB500 route, it goes more for sub-bass extension, then mellows out in the higher bass/lower mids, roll offs where appropriate to keep the sound balanced, and smooth. Another roll off in the lower treble. Just a bit of sparkle.
Detail retrieval is inferior to some other 'phones in the price range. Superlux, and Grado have the Hesh beat in detail, and separation, and of course, headstage, open vs closed.
The Hesh perform much better with classical, acoustic, hardstyle/freeform/jumpstyle/hardjump/hard dance/etc. It isn't a problem with some genres of metal, but there was an obvious distortion, probably some sort of driver grattle, when playing early thrash, german power metal, and some european power metal.
personal issue: The cups are BARELY circumaural. They pinch my earlobes. Glasses-wearers, and people who love earrings, look elsewhere.
For 60-65, you can't go wrong with these. I'd argue these are probably the best basshead cans in this price bracket.