It's a trade-off. Yes there is vertical lobing in the crossover region, but the power response takes only a minor dip at worst. Most listening is from far enough back that the vertical lobing in the crossover region isn't obvious when you go from sitting to standing, probably because the vertical pattern at high frequencies is pretty uniform. Indeed, I've had speaker designers remark unprompted that they can't hear the crossover. Having a round pattern puts more energy into the reverberant field than a rectangular pattern of the same width, but at the expense of increased floor and ceiling bounce energy. I don't know which is the ideal way for that trade-off to go.

Another reason for my choice is, the DDS waveguide is available over-the-counter and comes close enough to what I'd ideally want that I can work with it. The cost of having a custom waveguide (perhaps a bispheroidal) designed and molded and manufactured is beyond reach of my R&D budget at this point. That being said, one day I'd like to do a system with an oval-patterned device, perhaps a bispheroidal. It would look embarassingly like a 4Pi!

Duke

Another advantage of a rectangular horn is that you can go to a TMM (or would that be HWW?) format and get vertical as well as horizontal symmetry. I tried modelling symmetrical MTM (WHW?) cnofigurations but unless the crossover is quite low (or the horn too narrow in the vertical plane to maintain reasonable pattern control) the woofers end up too far apart and their vertical lobe is too narrow, in my opinion. Of course you'll still have the inevitable vertical pattern "pinch" at the crossover frequency.

Have you done any dual-woofer speakers? I don't recall seeing any, but then presumably not everything that happens in the lah-BORE-ah-TORE-ee enters your product line-up.

By the way, best of luck with your heat-pipe patent!

Duke

The way I implement such a system is to put a subwoofer below or near a three or four π loudspeaker. I know this is something you're familiar with. Having them separate lets the user have some configurability. That way you can put the subwoofer off to the side a foot, and the mains on a short stand, so the midwoofer is in a different location in all three planes. Overlap them through the bass range for best smoothing.

Another way I implement something similar is in the π cornerhorns. The woofer is low enough to the ground that it doesn't suffer floor bounce. The midhorn doesn't suffer floor bounce because of blending with the woofer. Its response is low enough to smooth some of the higher modal range. Subs can also be added to this configuration to further smooth the lower modal range.