Discussion of the S3 and
S4 seems to have completely dived off, but now I've got mine, and ready to discuss them.
So the awfully explosive nature of the S4 (aka Z1)
has tamed down significantly, and now it is just a refined U signature, more than V-shaped. In fact, that U-shape and need for ~100+ hours to get it fully broken in reminded me of the famous JVC FX40, which I also have. I broke that out of storage and sure enough, they are massively similar, in all sonic ways. Now I might also add many more hours to the ED4 and see if it does the same. I still can't tell with certainty if the only differences between the S4 and ED4 are the number of hours on them. (My S4 has more, I gave up on the ED4 too early perhaps.)
I have the
S3 now, and out of the box it is great.
Somewhat balanced with a mild extra kick in the bass.
Both of these can compete (with more evaluation time) for my favorite KZ along with the HDS3, and maybe the EDR2 when it arrives. But these, IMO, are ahead of the ED4, ED8, ED10, ATE-S, and ZN1 Mini, which I also own.