Currently i use a bi-amped system with fullrange driver and bass in closed boxes. Crossover frequency is 200 Hz. All amps are push-pull tube.

I would like to construct a similar system with a front horn for the full range driver and something similar to the 10 Pi for the bass. I am interested in SE Amps as a next project, so efficiency is important too. which driver would you use for a bass horn which is active to 150-200 hz?

Has anyone built something like this. Any plans, dimensions, and or reference material would be very much appreciated.

Thank you.