Fascinating thread! An employee of Altec Lansing in the mid 1950s told me a funny story years ago (which I may have previously told here). A foundry in the L.A. area had been casting 811 horns in great numbers, and also welding the halves together before delivering them to Altec for painting. Some bean counter did not like the expense of the welding operation, and said that Altec could do it cheaper in house. Soon large piles of half-811s were deposited all over the factory, dirt clods still clinging to the parts from the casting process, and the in house efforts at welding proved unsuccessful. Before long the foundry was once again given the task of welding and things returned to normal.

Coelacanth, the initial throat portion of the H811b appears to have been designed to narrow the directivity of the high frequencies to partially equalize the on axis resonse. This is not a great solution for the falling power response of a compression driver, as the on axis response and reverberant field will vary greatly in high frequency content, which our brains interpret as unnatural. I would be tempted to model a horn similar to the 811 where the major flare portion maintains itself back to the driver aperture. The horizontal axis should (as designed) maintain the driver's power response to the limits of the straight horn walls, the driver's falling power response being EQed in the crossover, resulting in a more natural listening result. Just a thought, anyway.