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Well, I've never tried one of those. In spite of that, I'll forge ahead with an opinion. (You know, the whole, "fools rush in", paradigm).

It looks like an attempt to "acoustically horn load" the sound hole output. Given the length of the horn, by best guess, it could only be effective at high frequencies. You might get a better idea about "cutoff frequencies" by investigating audio high frequency drivers, which are intended to be mated with a dispersion horn.

However, many contemporary loudspeakers have the bass reflex port, horn loaded. Allegedly a CAD feature. Allegedly to help damp out resonant peaks.

So, since the sound hole of a guitar functions, at least in part, as a reflex port, the science behind this is arguably sound. (Pun NOT intended, but I'll take it).

I doubt if this is something you'd want to sit around the living room using, but who knows.
Last edited by Captaincranky at Mar 18, 2012,