I have not investigated all 12" drivers but the ones I simulated wouldn't go. I'd imagine with a phase plug one could extend HF response pretty far though and keep it within +/- 3db.

I'd imagine a tractrix or exponential flare directly on-axis with a high DI may be able to reach 2Khz but polar response would be poor as the expense, off axis response is very important (at least to me).

What driver and horn are you running? Is response within +/-3db from lower cutoff to 2KHz? Have you got a measured response curve that you can post? Id like to see what your doing.

Adrian