The goal of this mod is to allow easily replacing cables and hopefully allowing DPA 406x mics to last longer by expanding/stiffening the area near the mic element as well as being able to break away if tugged too hard.
MMCX connectors are the same ones used by newer Shure and Westone IEMs, so you should be able to use any cables (usually 1/8" mini) for those IEMs with these mics.
[Edit: be careful about terminating your own cables, at least the Shure IEM
cable I have has spring-loaded male connectors. The MMCX plugs I got from eBay were not spring-loaded and will cause dropouts and popping due to vibration or movement]
From what I've read, MMCX connectors are only rated at 500 mating cycles, so these connectors do wear out faster than mini plugs, but might only swap cables when they wear out (or maybe after a few dozen shows).
Getting the coax pin through with the inner DPA cable was tricky since it's soft, so I used a single strand of thick copper cable I had lying around in between the pin and inner DPA signal cable so it was easier to push the pin through. There's a small piece of heatshrink to keep the inner pin from touching the shield.
The shield was easy with a crimper + some solder to reinforce.
Then I put some heatshrink on top of the crimp. For the second (better looking) mic, I put a piece of drinking straw over the shrink wrap and used liquid electrical tape to reinforce the insides a bit more. Then I put another piece of heatshrink over the straw.
I only used an inch of cable on the second mic, but for the first I gave myself some extra room with the first mic and used around 4 inches, folded over and covered in liquid electrical tape + heatshrink. I didn't use a drinking straw with the first mic.
I'll update this if/when a mic completely dies