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Leach throat size vs. Keele/Edgar size

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Been trying to design an 80Hz M=.6 midbass folded horn extending to 500Hz+ with an EVM15L. I'm getting a conflict with the various design approaches. Edgar advocates Keele's optimum throat size, which puts the throat in the 80si range, while Leach's is in the 30-36si ballpark (just winging these numbers from memory). The 15L fh is around 344, according to Keele/Edgar. With Leach, it comes out to 700Hz+.

I keep seeing discussions stating a minimum length horn of 1/4 wavelength of fL, which for 80Hz, would be about 42 inches. Leach's throat size calcalates this length. However, using Edgar's throat size, the horn is only around 32 inches.

What gives? What are the tradeoffs between the design approaches?

Also, Leach says to reactance annul the driver around 60Hz. Doubt it.

I remember reading in the "Show Horn" article that Edgar expressed doubts about Leach's formulas, but they do bring about proper length. Edgar also thought "a" (Vas/Vb) was an independently adjustable parameter, and seemed to be able to annul anyway.

It would seem the shorter horn of Edgar would cause reflections and roughness as compared to the Leach model. Also, doesn't a smaller throat help extend fh? It would seem important to extend up as high as possible to cross over to a compression driver.

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Topic - Leach throat size vs. Keele/Edgar size - pooge 13:48:05 06/07/03 (51)
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