[mclldavidson]

It didnt cut in half but put a gash in it and they dont work now, can I fix this?

 

[liquidzoo]

Sure.  You can either re-wire the existing cable or (potentially easier) replace it with one of your own.

 

[mclldavidson]

Do you have a tutorial for me rewiring it?  Also where is the cheapest place to get a replacement cable?

 

[liquidzoo]

Depends on the wire you want to use, I suppose.  Guitar Center has some Mogami 4-core that would be good (I've used it).  Mogami W2893 (from Redco) is better as it's more flexible.  It can be sleeved with Type 1 paracord really easily.  Either one you would probably want to remove the outer sheathing and braid the 4 cores.
 
For a tutorial, I've never opened ATH-M50s; but there are some other posts that should detail it.
 
http://www.head-fi.org/t/553483/ath-m50-removable-cable-mod
 
Or a video