I am planning on building a couple of single ended amps - a cheap one based on 2x CMOY boards and then hopefully a single ended valve amp once I have saved up some more pennies. Because of this I thought converting the T1s to have detachable cables would be good so I could have a standard cable and a balanced/single ended one without lots of chunky adapters.
 
I have done a similar mod on some DT770 in the past but there is slightly less room in the T1s so I was not sure if it would work but you can just about squeeze a miniXLR socket in there and still get them shut.
 
Here is a vid of the dismantling - I could not get the old cable out without cutting it in the end but I was going to cut it any way so it was not an issue

 
 
I used the mini 3 pin XLR socket so you can have + - and shield connections and used a dremel to widen the holes

There was not enough room for the screw on nut that is supposed to hold it in place so I had to use hot glue to secure them and made the hole as tight as possible so they can't be pulled out
I went with the the standard layout of 
Pin 1 shield
Pin 2 Positive 
Pin 3 Negative 
 
Then bridged pin 1 and the barrel so they are both connected to the shield - I kept the end of the cable to use to connect the shield and replaced the other internal wires with PTFE covered SPC the same as I am using for the cable - 2 x 19 strand cables 
 

 
Then just needed to neaten up the hot glue a bit and wang them back together.
Then I pulled them apart I pulled off the mesh but then found it is pretty much impossible to get the original beyerdynamic mesh back on because o the way they are constructed so They have the silver mesh underneath exposed but it goes quite nicely with the overall look
 

 
 
 
If you have any questions - just ask and if you have any suggestions for a DIY single ended amp to go with them for someone on a tight budget let me know