Heil AMT-1a's What do those pots DO?

[sudon't]

Hey ya'll!
I know there's a couple of Heil freaks out there, and I was thinking you might be able to answer a couple of questions I have. Namely:

What exactly do those pots on the crossover do? I'm thinking that the High Frequency Level Control simply attenuates the HF signal. It's essentially a volume control for the AMT so you can balance against the woofer. Yes?

But what does - or actually, how does - the midrange adjustment work? What frequencies does it affect, by how much, and how, exactly, does it do so?

This is a 70s vintage AMT-1a.

 

[automojo]

The controls operate in a linear fashion, as opposed to rolling off. I can't recall the frequencies, but genrally the one control presence/brilliance l-pad controls from 1200hz to beyond 23 khz.