2x12" + 1x1" midrange-top?

Hey there!

I have very little experience in the field of designing speakers, and would like to get some help regarding a design of a 2x 12" + 1x 1" midrange top to put on top on some 15" or 18" subwoofers.

I planned to put these drivers in:
2x Fane Sovereign 12-300
www.fane-acoustics.com/prod_details.aspx?pid=203

1x Eminence EPSD2002 1" driver
www.thomann.de/dk/eminence_emd2002l.htm

1x B&C ME 45 1" horn
www.thomann.de/dk/bc_me45_1_alu_horn.htm

I would like a design like the X12 design by Rog Mogale.

How do i make this design?