[Apolyonn]

I've had a pair of HD202's for awhile, and after running across the EH 350s, I started entertaining the idea of converting mine to open back.  I couldn't find a whole lot related to this idea on the net, so I figured I'd just ask.  Is converting [any set of] headphones to open-back a bad idea?
 

 

[RobustOrange]

I wouldn't recommend it. Open backs are specifically tuned to do their best as an open back, same goes for closed. It would be like taking a pair of Grados and duct taping the grill on them shut.

 

[ssrock64]

It's not like it can't be done, but it's very likely that they'll sound like complete crap if you open them up. All of your bass impact (which isn't exactly huge on the lower Sennheiser range to begin with) would immediately diminish, among other issues.