I just acquired an MDR-Z1R and frankly found the sound to be mediocre. Soundstage certainly deserves special mention, and the bass has a pleasantly thick, voluminous, meaty character. Two main quibbles: overblown bass that permeates the rest of the frequency spectrum and recessed, jagged treble.
My initial suspicion was that the stock pads were the limiting factor. I found that if I pressed the pads against my head to bring them closer to my ears, the bass would be brought down, and the treble brought forward. My understanding from the
ZMF pads guide was that thicker pads tend to create a more uneven, V-shaped response, whereas flatter pads result in a smoother, more linear response.
With this in mind, I swapped the stock pads for a pair of ZMF BE2 Lambskins. Sure enough, this evened out the tonal response very nicely. Bass is much better controlled and defined than stock, and treble is much smoother, with greater presence, extension, and detail.
Still, I felt the Z1R was a tad dark and bass heavy for my tastes, so I took things a step further, and damped the cups with cotton wool. Now we have a winner. Compared to stock, the modded Z1R is significantly--if not dramatically--improved in terms of clarity, transparency, separation, detail retrieval, and linearity.
For context, other closed back cans I've owned include the Lawton Level 1 Fostex TH900 MK2, Klipsch HP-3, and Beyerdynamic T5p G2. I currently have the ZMF Auteur Classic, Sennheiser HD 800 S and Neumann NDH 30 on hand, and perhaps the best praise I can give the modded Z1R is that I would readily choose them over all the cans listed above.