[16 foot folded horn subwoofer]

hmmm, looks like it is upside down. Is the nether end finished? Could it be missing spiked feet?

I also saw a folded horn subwoofer at http://www.decware.com called the OS32 or some such. He doesn't sell it; only the plans.

[Horn Expansion (Design)]

So,

has anyone figured out how large a bass horn would have to be to be flat from 20 Hz to 100 Hz?

I once read about a hi-fi executive back in the days of mono who had a stereo (oops, mono) room where one entire wall was the mouth of a horn that went back 40 ft.

I have fantasies of building such a horn in my basement, starting at one end and culminating in a slot opening near the floor in the rear.

[SET and Jensen oil caps in crossovers]

what an amusing thought to have your crossover sitting next to your amp, with a short(!) speaker wire to the crossover, and three burly boys from the crossover snaking into the speaker...

Just not clear on what you mean by your references to changing values on networks -- you are talking about the stock AA network being modified?