About your crossover, maybe we'll look at your crossover with a signal generator and scope and set it up with that. I think there's lots of people here that would be thrilled to have an active crossover using tubes, and to know the component values that should be used to provide the appropriate response curve for their horns.

By the way, Mitch left for Norman this weekend, bringing his Theater Series four π's with him. They're the same size as your Altec 416 π's and are tuned similarly too. The port isn't as long or have as much cross-section area, but the Helmholtz frequency of the Theater four π Speaker is 25Hz, and the Helmholtz frequency of your 416 π Speaker is 30Hz, so they're pretty close. I'd say the two woofer motors would be interchangeable in either cabinet.

I don't know if Mitch will be one of your students this semester, but we'll all get together sometime soon, in any event.