So I have 2 pairs of MDR XB950BT where the one broke the part that holds the cup and the other broke the headband.
So I have created these 2 options for others to to be able to fix their headphones as well.
The first one uses all the original parts from the headphones and only replaced the part that hold the ear cup. With this option you will need to desolder and un-snake the cable from the original then snake it back through the new printed one. Make sure of where the wires were soldered before, you cant just rely on looking at the other side as the wire older is switched but they are marked.
For this one i suggest you add supports just from the bed to the part and not inside as they would be hard to remove and in my case were unneeded as they are just round tunnels.
The second option I used parts from the EQ1 headphones uploaded by 3DCentralVA.
I modified the headband so it could fit my design.
You will need to print more parts but you do not have to solder unless you find that easier.
You could just continue to break/cut the plastic to free the cable (you don't have to break the plastic on the ear cups).
For the MDRXB950 original piece only place supports from the bed to the part.
You may need to sand the circular parts that enter the earcups, and make sure to completely remove the support material or it will be too tight.
The slits on the circular ear cup connector is to be able to reuse the blue rubber seal the original headphones come with to avoid dust getting into the headphones.
I have included a photo of the internal ear cup both left and right, for reference of the wires and so you can see what you will be getting yourself into.