Fostex TH900mk2

Update! A number of sellers on AliExpress have connectors fitted for the TH900. I got a pair, and they work well. Example link

The Foxtex TH900mk2 uses a similar, but not the same tip connector as the Sennhieser HD580/600/650. The locking notches in the tip are a bit different, and the connectors need to be inserted a little bit more on the Fostex. As a result, cables are most compatible. Oh, the Hot and common pins are reversed between the two companies, but since they are reversed on both channels, it shouldn't be an issue.

The only Fostex TH900mk2 connection tips that I'm aware of are from Furutech, part number FT-2PS-F for Fostex headphones. I haven't seen them, but Furutech claims they are for Fostex. Moon Audio link ($46)

Some of the connection tips are one piece of plastic that are very hard to solder without melting the plastic. Some of the connectors have a main section and a shell that snaps on. These are easier to solder, and what I used.

I got these from AliExpress. I think about $25/pr. I filled the shell with hot glue, attached them, and filled the Y-Splitter with some hot glue as well. And the final product: