I worked for a sound system installer back when those things were still shiny (ca. mid-70s), and have used and heard hundreds of them. Believe it or not, the <$15 Pyle waveguide that Duke uses blows 'em away. Altec and JBL both made some really cool looking stuff back then though, for sure.
+1 to this. One of my college roommates built a system with one of those 811 horns, and it sounded like a megaphone. Impressive looking, not so good sounding. And yes, he took great care to get the crossover point right. They're very efficient and can fill an auditorium, though.