When I made my headphones in the old stinky helmet I just wanted to experiment, and its been a lot of fun.
I have tried quite a few different drivers in them.
Some headphone drivers really reply on that closed cup, some don't, but the painful part is you cant just buy them and try.
I salvage broken headphones and try them when i get them, I put an add for a while, $5 for your broken headphones. provided they where not cheap headphones.