That was really easy. Props to Sennheiser for a very end-user friendly design.
1. Pull off the pads
2. Snap off the headband
3. Pull off the grill
4. Pull out the bottom part of the headband ring attachment thingy.
5. Put in the new driver (Sennheiser calls it System 300R, and system better describes it, since its a driver in a housing with the input jacks for the senn headphone cable connectors)
6. Reassemble.
Interesting side note: the drivers I received are the newer, white drivers, and the old drivers were the black ones. Whether the drivers are truly different other then the color is a subject best left to one hundred million HF threads, but the difference in sound to me seems readily apparent. Bass has tightened, and both treble and midrange are slightly more forward. Of course this could just be that we're dealing with brand new drivers.
So without further ado:
Moo monkey moo monkey make modern milliseconds
Grrrrrrrr gravy grrrrrr gravy get get go ghost
untz untz untz untz untz untz untz
night nipple netherworld
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volume be loud blowin' my fool head. peace i'm out.