So, I've built my first tapped horn. Well really, tapped pipe. See here: http://techtalk.parts-express.com/sh...d.php?t=212596

From the FR and impedance, it looks like I managed to get the length wrong a bit (still trying to figure out why), but otherwise the output is pretty close to what's predicted by HornResp (once it's re-adjusted for the correct length).

I'm now considering trying a proof of concept with a larger driver. Any suggestions for cheap and decent 12" driver with an Fs ~ 50 Hz and a medium Qts?

This one looks interesting, but unfortunately no parameters are listed (I'm guessing Fs is around 50 Hz because of the quoted FR range): http://cgi.ebay.com/12-TS2-HIGH-EFFI...4.c0.m14.l1262