On the subject of horn-loaded cabs, there is a book called Loudspeakers for Musicians by Bill Fitzmaurice that has 6 or 7 horn-loaded/folded horn projects of various design and difficulty -- all of which are for sound reinforcement or MI use, I haven't built any yet but it's a very interesting read. The author is (to say the least) a proponent of front-loaded folding horns for MI use. You can get the book from Parts Express -- it's from the Speaker Builder series.
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