Its funny how almost every company does it,the little box.Linkwitz shows how a 4" can only be used so high ,2khz? before its radiation pattern is less than 90°cone,meaning 3ways are a must for a decent LE system.See the publications section. He even applies bucket brigade delay to fix up some of the fixed delay involved in the active filter chosen,i like this approach.

I too dont like the idea of one woofer gradually getting more directive-then at Fc omnidirectional tweeter!A very sudden change vs Waynes and Geddes approach to have more uniform,more constant Directivity! Ive just got to try it when funds allow!
harmon kandon have some whitepapers on the mainpage,they too are looking for uniform DI but most dont realise that the right horn can do this.

btw just looked at some cheap PYLE bullet tweeter,the FR looks amazingly crazy!

Cheers
Mike.e