Marty these 90 degree horns are fascinating and an often overlooked branch of horn evolution. D.G. Blattner of Bell Laboratories received U.S. Patent #1,996,743 on this type of horn in 1935:
ACOUSTIC DEVICE - Google Patent Search
The late A.J. May of RCA also researched these horns and built prototypes. There was at least one production model of 90 degree horn built by RCA of some fibrous material. Mostly it was the Western Electric and later licensed Altec horns that were produced in large numbers.
There were also numerous European 90 degree midrange / high frequency theatre horns built, but they don't appear to use the throat shape to achieve wide horizontal dispersion of high frequencies like the W.E. horns.
I had a plastic pair of Altec 32Bs years ago, but let them slip through my fingers. Never measured them.
Bookmarks