I bought the Yamaha EPH-100 about 2 years ago and wanted to mod it after I saw the Yamaha EPH-200 which is simply an mmcx version of the EPH-100.
The teardown process wasn’t so easy with EPH-100. The 6mm micro dynamic driver is sitting on the edge of the nozzle and it’s deeply attached to the tiny body in an aluminium shell. On the first day, I tried some heating and acetone to loosen the glue and tried politely with no luck. On the second day, I decided on a more radical solution.
Only with some real force, I was able to teardown EPH-100’s nozzle from the body. Finally 
As you can see the nozzle part is actually the IEM itself, the back shell is so tiny, only holds the cable hole, the nozzle and a couple of mm in length backwards.
First I tried to make the cable hole a little bigger for the mmcx connector and screw the connector into the body. But there is so little place inside the back shell it wasn’t tight and strong enough. Sure I could use some epoxy on the outside to glue the connector from the outside but I know I wouldn’t like the look. Then I decided to place to the nut of the connector on the outside of the shell for a cleaner look and stronger fit.
Looking good right? But there is a detail which is very important that I realized later. The body where I decided to apply the nut is very thin aluminium. I wanted to carve it more for a perfect fit and look but crushed it while I was working with pliers. What a bummer!
I needed new shells! I don’t have many options in the house, only wood that I can shape or carve with the Dremel tool. I had some samples that I bought before and decided to use mahogany wood for its colour that can match with brass which is used on the nozzle metal, which I realized after sanding it.
After a couple of hours of sanding and carving, they finally got their shape. I installed the mmcx connectors and continue carving until the nozzle fits tightly.
The back of the nozzles was covered/blocked with the cable itself for tuning purposes I guess. I decided to change this in the name of testing wood shell acoustic changes if there will be any. Unblocked the original cover and put a piece of foam inside.
Then I soldered the cables. Placed the nozzles to the wood shells with just some glue in case I needed to open them later for tuning. I also closed the back of the wood shell by glueing the old wood faceplates from another IEM (Geekwold) and done some final sanding.
How do they look? I was so frustrated after I crushed the aluminium shell but in the end, I am so happy with the wood shells which was not my plan at the beginning obviously. They look awesome and one of a kind
There is more. The sound. It turns out that the Mahony wood shells affected the sound much more than I imagined. If you are reading this you probably know how the EPH-100s sound. Add a huge soundstage, more dynamics and somehow uplifted mids to the original sound. I present you the Yamaha EPH-300