I don't even need to press the free drivers against the ear to hear the drastic bass difference between my PortaPro driver and Ksc35 ones. The bass/lower mids just drowns out everything with the portapro driver even when it's hovering against the ear, completely different from the Ksc35 driver which has tons more clarity and less bass/lower mids. It's not even a matter of short-term auditory memory / swapping time, they are starkly different-sounding to me. Heck even the Ksc75s sound closer to my Ksc35 drivers than the Portapros ones.
It may be a long shot:
http://loveray.blogspot.nl/2010/12/how-to-identify-fake-koss-porta-pro.htmlI have owned (and even traded a few) KSC50's and even still keep one of those for spare drivers which are the predecessors of the KSC75 and have 3 KSC75's (one was used by the wife before I gave her a HD238). One of them died after I soldered off an intermittent wire. Have 2 of those left. 1 at home, one at the office.
Had 2 PortaPro's (both sold now) and 1 SportaPro, also sold (even had a KTX-Pro 1 for a while).
I found all of them to sound closely the same when used under the same conditions and would not be able to tell them apart blindfolded.
It may be my lack of hearing abilities (have been accused of this before
) but seriously doubt this.
There may be some spread in production but a very obvious spread I have not encountered with all the Koss's I owned.
Except for the KTX-Pro1 which is a completely different and dark headphone.
Indeed it is likely something else is going on.
When I have some time I will also measure my KSC75's and KSC50 (already measured the KSC35) which may not be accurate in an absolute sense but can be used comparatively.
Do not have Portapro and Sportapro any more.
