This repair shouldn't take longer than 15 minutes. (That is if you allready have the parts)
Step 1: The Parts
2 Meccano Bolts
2 Meccano Nuts
The tools I used were the standard Meccano screwdriver and wrench, a knive, a screwdriver and a drill.
Step 2: Take the Headphones Apart
Remove the cussion in the center. With this Sennheiser model, the cussion is glued to the headphones. Pry it off carefully.
Note: Be careful not to lose the tiny screws!
Step 3: Start Repairing
Once you think you've got the right shape, measure where you will need to drill the holes in the headband.
Once the holes are drilled, insert the bolts through the headband and Meccano strip. I preffered the nuts on the inside.
Step 4: Reassemble
Important: Make sure the wires aren't twisted when you put it all back toghether.
Step 5: Be Proud of the Result
after all, a penny saved is a penny earned!
You can always paint the screws black, so they're less noticable.
Also, if you don't have Meccano lying around, search for some alternatives. You can always try finding a similar metal strip in your local hardware store.
Thank you for reading. This was my first instructable, leave your toughts and comments but be construcive please. There could be a lot of typo's here, since English is not my native language. Sorry about that! If you got any questions, I'll try to answer them in the comments or add them to the instructable.
Have fun Re-using your old broken headphones!