The Professional Series four π uses a JBL 2226H (8 ohm) and a JBL 2426H or Eminence PSD2002-8 compression driver. The horn is a 90x40 radial design, and the design crosses over where the midwoofer matches horizontal directivity with the tweeter. Best listening area in the vertical is within the 40° pattern of the horn. Much above or below this and upper midrange and treble will suffer.

I'd be happy to sell you the kits minus the woofers, so if that will be helpful, we'll do it. You can also source the parts locally.

The 2241 is an excellent woofer. They work well in a wide range of cabinets, from 4.0ft3 to 16.0ft3 tuned to 30Hz. for subwoofer use, I think 8.0ft3 to 16ft3 is best, and I've built plenty of them that were 10ft3 and they sounded great. So I'd definitely approve of your choice to use a 12.0ft3 box tuned to 30Hz.