I have been helping a friend of mine getting started with a nice little 3-way project.
2235's (not yet acquired), 2425's and 2405's.
We wanted to crossover at 6-800Hz and 8-10KHz. The smith horn was not an alternative since it would be very large (wide) when redesigned for 1" driver and a crossover frequency of 6-800Hz.
He liked the look of the Altec 811, so we took a tractrix contour and recalculated it into a sectoral / biradial horn.
I have made a prototype from particle board with my belt sander.
The first response graph is really encouraging. Will probably make jig for routing the profiles more accurate.
The horn has been painted black since this photo. I took measurements before and after painting. The paint smoothened the response curve.
I have not played music on it yet, but hope to do so soon.