Hi Dave

re; mating the 2435 to the 2397.

FWIW;

(a) If it was my project, I'd ask Ken Pachkowsky to take an internal lip to lip measurement of the 1" Smith Horn, as found in his Westlakes.

(b) Then I'd look the Mr. Widgets' measurements to derive the average height
inside the more or less horizontal part of the H9800 diffraction portion of that horn.

(c) Then, see if you can get a measurement of the diffraction Slot-Opening for the large Vertec SR box that uses the 2435.

(d) Take a measurement of the ( 2397 ) height between the top & bottom plates.

(e) Compare these four figures. Some design commonalities should come to the forefront. What to determine ; The best ratio of ;Compresson Driver throat exit size to distance between the top and bottom horizontal lenses.

Some History :

The predecessor to the Smith type horn is the "parabolic horn" as described by H. F. Olson ( of RCA ) in the mid fifties. Drawings show a virtually identical horn - though minus any internal vanes. I believe the aspect ratio he used was .5, when comparing the drivers' exit size to height between horn bells. It's the velocity buildup that occurs when forcing sound through a smaller apeture, then followed by presenting a wide low-pressure horizontal zone, that forces the sound to spray and spread. The reason a one exit driver coupled to the 2397 doesn't work is because little to no pressurization actually happens. Additionally, the 2327 adpater goes the wrong direction from a pressure perspective.

My Conclusion : I'd be thinking that I need to shrink the mouth height somewhat for this Smith horn ( for use on a 1.5" exit driver ).

Just my thoughts

<> Earl K

EDIT : Alex has asked ; What are the purposes of the vanes in the Bell ?

The original parabolic horn without the vanes shows great dispersion in the upper regions. The book has polar patterns included. It's in the lower octave that dispersion suffers ( without the vanes ). This leads to an assumed conclusion that just can't be tested till someone makes ( & tests ) a large Smith Horn without Vanes. It might be worthwhile to ask Ken if the small 1" Smith Horns ( in his Westlakes ) have vanes .