Ribbon Tweeter Resonant Frequency

A sincere thank you to all who participate in the discussions. I have really learned a lot. I'm an electrical engineer with a background in switching power supplies, audio amplifiers and analog design. And have recently been bitten by the DI speaker bug.

I'd like to build a long ribbon tweeter for a near field line source. And want to cross over at about 1.4kHz.

So my question is, how do you determine the resonant frequency of the tweeter? I would think that it is only based on the density of the foil? And if you have active EQ, can you run below resonance?

Best regards,
Gregg Stock