I used to own a pair of Koss Model 1A!
For those that don't know or remember these beauties, they were a truly full range that were comprised of separate tweeter, treble, mid-range and base panels.
They were very good! Cohesive, transparent, imaged amazingly well, with quite good dynamics.
I sold them to a friend, so I get to listen to them fairly often. I still miss them though...