I picked up some old realistic portable phones, in mint condition. at a thrift along with a Sony discman I have to say they sound as good if not better than the Koss titanium driverheadphones I once had.
The bass is tight and the highs are crisp. Maybe a bit on the bright side but not overtly so. They lack the rattle the koss had I can hear the sticks hitting the drums and extra detail that the sony MDRZX300's I have and the audiology and Nakamichi cans don't even pick up, or don't pick up as well.
I can even hear the cymbals ring in some loudness war plagued tracks. Sadly they make all my low resolution Mp3 CD's sound even muddier.
They are completely open so there is no isolation, if I put my hands over the grilles they sound muddy and hollow.
I was going to get the koss port a pro's but I don't think I need them now. I heard they break too easy.