I have the Vince Gill album, "Ballads", from 2013....his voice just isn't as smooth and clear with the 560 to my ears. Linda Ronstadt's voice has a quality that reacts in a similar way, as well as Allison Krause! I don't have a problem EQing the 560 while I listen to them. Also, I have quite a few aftermarket DIY cables so I don't use the stock cable. What I have is more resolving, imo....but I will not discuss the differences in the different wire used in the cables. Even HFM uses cables of different design amongst their headphones. So lets just say cables don't make a difference to avoid any arguments about them. I love the 560 very much with my setup, which involves a lot of different pieces, and at different times that can change with small changes. Also, this is something that was not that noticeable with the preorder Rev.1 with the old ear pads.
I listened to some Allison Krauss while you were typing this up. Couldn't find much wrong with her voice. Looking for that Vince Gill album, it wasn't on Spotify... Tried a random album again, not hearing. At the same time, I don't know either of these artists that well to really say much. IMO, I think it might be the 4 kHz boost that the new model got (that's the main difference between them). HiFiMan, Fang really, tries to hand pick their cables (whichever sounds best in their setup is used as the stock). Either way, I doubt it's the cable. I tried :p LOL. Still think it's the 4 kHz boost.
I added a boost at 2khz, like TMRaven suggested, and it does smooth the transition for me a bit. But if I shut all of the EQ off 2 - 4khz, I lose the enjoyment I had. Allison Krause, "A Hundred Miles or More", surely sounds better to me with the EQ on, seems to me that the hump of the 560 at 3 - 5khz isn't needed, but that is just me....I'm not trying to please anyone other than myself. Most in this forum would stand behind the HFM sound anyways, maybe I should have kept the preorder Rev.1, but I decided the total package of the production Rev.2 was better, even if I have the need to EQ to make it sound to my liking. IMO, IMO.