Sorry for the double post, and for derailing your thread, Tai...
I went ahead and burned in the modded PK2s overnight. They seem to be slightly more open-sounding, but I can't help but feel like I'm listening to a different earphone than others (when looking at reviews of the original PK2). I tried searching the forums, seeing people commenting about the lively sound and smooth, musical mids, and as I read I became more and more confused, thinking I have two broken pairs. That is, until I found this post
which describes what I'm hearing almost exactly. I'm wondering if there is a quality control issue, and if there is, does it lie with Dasetn or Yuin?
For the heck of it, I decided to use more porous and thin foams; this seems to work much better. The foams that came with my modded PK2s are much too thick. The PK2s now sound much more transparent. I'm still not used to the midrange coloration, but I'll give these guys a little bit more time before I decide what to do with them. I will probably sell one of the two pairs though as I don't see any reason for me to keep two of them.
Going back to your question about the mids, Danneq (sorry for missing it the first time):
The peak I hear isn't quite in the upper mids, though I can't pinpoint exactly where it is. All I can say is it's a similar peak / resonance to what I heard with the Hifiman (then Head-Direct) RE2, which led me to selling them. I'm very sensitive when it comes to mids, while I have a bit more tolerance for upper mids. That's why in general I tend to gravitate toward earbuds and IEMs with slightly recessed and / or laid-back mids, the Etymotic HF3 being a notable exception; I hear no such resonance with the Etys, strangely enough. I was kind of anticipating having the issue with the PK2s, but thought the increase in soundstage would help it out a bit. Apparently it wasn't enough for my cursed ears!
EDIT: Surprisingly, the thin foams seem to make the midrange resonance a lot less noticeable. I think these might work out after all!.Edited by kjk1281 - 8/22/13 at 1:35pm