I did some initial modeling with a 150in2 throat to support a pair of 15" drivers. The models looked pretty good, and I think the horn could be built in less than 40ft3. Naturally, the 12" version is even smaller, easily being less than 35ft3 to fit in a 4x4x2 foot box. I suppose you could use the same parameters as the LABhorn, if you wanted, i.e. rear chamber volume, front chamber volume, horn length and area. Using the push-pull configuration should have lower distortion because of the way the drivers are connected and pressurize the front chamber. But I'm not so sure there isn't an advantage using larger, more powerful drivers. I'll check the math and see, maybe build a model or two and test them.

Check out my other comments in the reply I made to Graeme. There's a quick drawing of what I'm thinking about there too.

My main focus was on decreasing even order harmonics entering the throat. There are a few good techniques that can be employed to do that, so it always seemed to me to be a good idea to do for high-quality and/or high-power systems. They are built at a price point that makes it more than possible, at least from my way of thinking.

As for boundary reinforcement, I think you and I would agree that all basshorns are built with that assumption. Most are built to work best when radiating into π space or less. Danley's bdeap has a smaller mouth probably because it is designed to be used in π/2 space. It's designed to be used in corners or in groups.

Wayne