The other day, the I finally got round to recabling my ATH-ES7's.  The reason for this, the cable was getting too short, after being breaking a about 20cm away from the plug.  There was nothing fancy used in this, as it is a temporary measure (although will be keeping the headphones still, I am currently waiting on a set of ATHA-500's for work, so these will become a spare pair).  I used a spare 3.5mm plug I had, some spare mic cable, (only 2 core, not quad cable), a short length of other spare audio cable I had (approx 3.5mm diameter, its used for creating the split).
 
Any questions, feel free to ask, but the more interesting bits are as follows.
Heatshrink, with bits of hot glue put in before shrinking, for the best join.
Heatshrinking every join.
Heatshrink over the plug, as the standard spring that came with the plug will not fit.
The cable, from the 'Y', to the headphones, is almost exactly 3.5mm.  No alterations of the housing was required, except for removing the rubber cable holder from the headphones (owners of them will know what I mean).
When inside the headphones, solder on the pads on the closest the center of the drivers, the front ones (which the standard cable is connected to) is shared with the very fine wire to the drivers).
 

 
Thats all that I can think of that is useful, hopefully it is usefully for others, if there is anything unclear, let me know, and I will attempt to clarify.

Hey,
 
I also recabled my ATH-ES7's this year. I decided to braid the new cable. Here's the finished product, with a four-wire braid and ugly while heatshrink to maintain the braid:
 

 
Forgive the crappy cellphone image...
 
I also took the liberty of changing it up to a 6.5mm (1/4") jack.