So after having a chance to listen to these for a couple hours, I feel like I understand the basic signature. To my ears the HD58X are a darker leaning headphone, and not just because of the bass, which I find detailed and well defined but a bit north of my ideal level, but because of a bit of a treble roll off. The midrange is fairly linear except for a dip in the 2-3k Hz, which has made female vocals sound a touch recessed and thin to me. The treble is good, but I do hear it as a bit veiled. I haven't ever heard the HD650, but it seems to match it's FR pretty closely. This is certainly no HD600 though, and I definitely prefer the HD600 in almost every category. Though in my personal opinion the HD600 is darn near perfect, so I'm biased. It's hard for me to say how good it's resolution is in comparison because of the darker sound, but I would say they fall just short of the HD600, but come close. That modest boost to the bass and sub-bass makes the excellent for EDM, older rock and metal, and any bass heavy genres. I also hear them as less agile and quick-footed as some headphones, being perhaps a smidge slower. And as other have mentioned, these have the smallest soundstage of any open back I have ever heard. My brain is still adjusting to the sound, and I like them the more I listen, but I think those that like a darker smoother response, or a bassier headphone that isn't V shaped will prefer them. They're certainly a refined
[ or good] can, and I think a lot of people are going to like them. Listening was done mostly through my AK70 and my Magni 2U. Though take my impressions with a grain of salt, I'm no professional reviewer