Well to get the point one of the mids went dead so I hussled off to the speaker city hoping they could fix it , oh maybe this is 10 years ago.
He sold me some very nasty pizo things that where not mids. So guess what ? I started reading all this stuff your guys designs and frankly the PI stuff is the only designs the would even come close to my old wonderful speakers.

I still have the cabs, and the crossovers. lovely back breaking walnut. these were a 4 way crossover with the so typical pots to attenuate the mids and highs.The crossovers are elaberate as far as anything I see in anything modern.

What I want is to make this cab usable the horn opening is 14.5x 4.5
with a decent 2 cubic foot below sealed. I know this about right for
alot of 12in drivers ported. but the opening for the horn? perhaps I can just seal it and use a horn on top?

Wayne! will you forgive me if I use your mid horn and a heil on top?
seems the to me that that air from the heil above 3k with what you have makes for what is called heaven .If....big one here we could just load the heil, to help the directivity? the throat is like 5.5 x 1.35? Maybe a bad idea.. but still no matter how much I look I cant find those mid horns that made everyone say , wow this music sounds good:)And yes I might dump the hiels and just buy your setup.

Maybe use the midhorn and compression horn, but then crossover to a supertweeter above 6kHz or so. Perhaps your Heils could provide top-octave duty. Keep us posted on what you decide to do. It looks like you have an interesting project ahead of you.