I ordered a pair of ATH-M50s last week and just got around to opening them up today and doing the detachable cable mod to them. I only bought these to sell (I had some Amazon credit that I wanted in my PayPal account instead of stuck on Amazon).
While I had them opened up for the detachable cable mod, I put Dynamat on the inside of the cup and cut a hold in the foam padding that's normally against the back of the cup. I had thought about doing this the last time I had some M50's but ended up not doing it. It made the mids come out a little more, there is actually MORE Bass, and more treble. I did that mod to the left cup before I did it to the right cup to see if I could hear a difference, and to decide if I wanted to reverse it or not. I liked what I heard and did the right cup as well (obviously Haha). If anyone has some M50s I HIGHLY recommend you try this, keep the padding you cut out just in case you want to put it back.
These headphones are for sale here in our classifieds.
BTW the hot glue strings have been removed Haha