Finally got around to trying the ZMF replacement pads on my HD600. (I bought the perf lambskin because of course.)
My initial impression is that the pad-swapped headphone seems more forward/in-your-face/aggressive and it also seems faster/more detailed to me, though that could just be the forwardness creating that impression. Or I guess that could also be caused by the change in the front-damping material. The imaging/staging doesn’t seem better or worse, but it feels like the sound is in a bigger space if that makes sense?
For the first song or two, I definitely preferred the stock pads, but these are growing on me the more and more I listen to them. Either way, the ZMF pads aren’t a 1-to-1 swap, they do sound different to me, so yeah, your mileage will vary!
EDIT:
I guess I should mention that the chain I’m testing on is Bifrost 2 → Quicksilver → recent model HD600.
Also, the size of the pads isn’t /that/ different, but it definitely feels like there’s more space for my ears in the stock pads, the ZMF pads feel noticeably smaller to me.