Well, I'm happy to say that I've been able to procure a copy of the crossover schematic from the folks at Harmon parts, which was a very pleasant surprise.
I have some questions about it, and I'm hoping that some of you might be able to help. The circuit is attached as a .png file. (Let me know if you need a different file format)
1. Is this a 3rd Order Butterworth filter? It looks like one based on the topology, but when I use web-based crossover calculators to determine values for a 3rd-Order Butterworth filter, I always get a higher value for C3 than shown in the schematic -- 5uF instead of 3 uF.
2. Why are the 2 uF and 3 uF PP caps bypassed by 0.01 uF PP caps?
3. Why does the attenuation circuit use two 1N5338B Zener diodes between the signal and ground, oriented cathode to cathode?
Any insights would be greatly appreciated!