My take on using undersized basshorns for PA is that it is a dubious compromise. I mean, on one hand, if you use several of them, it's a reasonable compromise. But then again, if you're going to compromise, why even go to the complexity of using a horn? A direct radiator subwoofer is exceptionally flat and easy to use. I think bass-reflex subwoofers get maligned too much by us "horn guys."

I've measured some pretty bad basshorns. Some of them have become pretty popular with enthusiasts that boast proudly about their one note wonders. I guess it's builders pride. Then again, like I said, when you get enough of them going, they smooth out a bit. Funny to watch a guy use two of them though. Yuck!

The thing that intrigues me is the hybrids. The transmission lines with additinal resonators for higher mode reactance annulling. I think that's a pretty good idea, a way to make a horn with a small footprint. Whatever label you put on them, transmission lines, horns, hybrids, half horns, stubs, resonating lines, tapped horns - the idea still has merit. Use the rear chamber for annulling the reactance of the first standing wave node, and then use additional resonators to annul the higher wave nodes. That's a clever approach.

Aaah, but then again, if you have the room for a full size basshorn...