[MiNe 109]

In article .com,
wrote:

Anyone know the model / brand of a 2-way headphone (meaning it had a
seperate woofer and tweeter in each side) that sold on the early 80's?
I used them as
a teenager at a friends house and I thought they sounded great but I
have never encountered anything like it before. These phones were
large but flat (they didn't
have a big cup but more of a flat plane that housed drivers).

"Two drivers" sounds like AKG, but "flat plane" sounds like Stax.
Neither fits both parts of your description: the AKGs have cups and Stax
are electrostatic.

http://www.stax.co.jp/Export/SR303e.html

Good luck!

Stephen