Thanks, that makes sense now that you mention it.  I guess I should go with wired headphones.

Regarding my question above about use during recording.  I just found this on the Sennheiser US website for both the 160 and 170:     "Note: while the sound quaity of these headphones is fantastic for any type of music, they were not designed for use while recording/tracking and monitoring...

I just discovered this discussion while researching wireless headphones.  I need them for use in a small recording studio to wear while recording guitar or vocals into a microphone while listening to the previously recorded instruments through the headphones.  For this I need closed headphones...