Copied from another thread. I have not built this version .... yet, but based on my experience using a Lowther PM2A and a pair of Eminence Alpha 15A's it should be an excellent performer.
Each channel is a Lowther PM6A, PM6C, or DX2 full range driver with two Eminence Alpha 15A woofers wired in parallel. I might be tempted to later add an Aurum Cantus G2Si for the very top if needed. A baffle 2' x 4' baffle will yield an excellent system that will produce ~96 dB/W/m and be -3dB at 40 Hz. I have all of the parts but have not had the time to actually follow through and build this system.
Active Crossover Settings
Low Pass - 200 Hz 2nd order Linkwitz-Riley
Hig Pass - 400 Hz 2nd order Linkwitz-Riley
Passive Crossover Sizing (classic 2nd order circuit configuration)
Zobel circuit across the woofers
Mills 4 ohm resistor
Solen 30 uF
Low Pass
ERSE 14 ga Super Q 4.7 mH in series with the drivers
Solen 130 uF in parallel with the drivers
High Pass
Solen 27 uF in series with the drivers
ERSE 14 ga Super Q 5.6 mH in parallel with the drivers
http://www.erseaudio.com/Products/14-AWG-1-63mmhttp://www.partsexpress.com/solen-metallized-polypropylene-capacitors.cfmThese would be my starting crossover values and I would tweak them by ear.
Hope that helps,
Martin