New Heathkit AS101 owner - First post.

[gearfreak]

I assume it has something to do with sound waves moving in an air medium through a restricted space.

*I think I misquoted, and was intending Fo, not Fc in my original.

Afaik, mouth area ultimately (perhaps as part of the expansion coefficient) limits Fo (cutoff). e.g. Tubas have bigger bells than trumpets. So you must consider that along with the length (path should be at least 1/4 WL, iirc)

I don't want to go on spouting bad horn math or mistruths , so I'll leave it to pickup later (or someone else can continue).