Lobing can be a non issue if it coincides with the natural vertical directivity of the horns. Or put another way, lobing can be used to improve compliance with said directivity, extending the pattern through the crossover.
Since Earl has been mentioned I would add that he doesn't see foam in the throat as ideal, saying that it will help more further out. This is because of the greater prevalence of higher order modes the further you go, and the greater volume of the foam it will pass through. I assume that some people like myself have been through using it in the throat due to not having a large enough bun of it to make full plugs.
Since Earl has been mentioned I would add that he doesn't see foam in the throat as ideal, saying that it will help more further out. This is because of the greater prevalence of higher order modes the further you go, and the greater volume of the foam it will pass through. I assume that some people like myself have been through using it in the throat due to not having a large enough bun of it to make full plugs.
Also,
..though he rarely mentions it, HOM's (which are still theoretical in this context*) are only of consequence only at high pressures - which (excepting very wide dynamics) are rare: pressures above at least 100 db.
As a result the "foam plug" in the throat, at least for a reduction in HOM's, is largely moot (..again, unless you listen at very high levels).
Now it could be that the foam plug (a large one that extends near the "mouth" of the horn) also helps with diffraction induced ripples modulating the pass-band above the horn's "cut-off",
BUT - a well implemented absorptive surround around the horn's "mouth" will also do this.
IMO the plug is the wrong move (..unless it's helping with a flaw in the throat profile like diffraction from a poor transition from driver to horn, and even then the better move is to fix the problem).
*while some have scoffed at HOM's, I'm actually not one of them - the smart "money" is on Earl here, it's just that HOM's in our context are largely a non-factor. Now sound reinforcement, club use, etc.. yeah - a foam plug of 30 ppi may well be something of a remedy for a real problem.
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Wise leanings I would say. The action of the foam is to attenuate waves more if they do not proceed directly out of the horn because their zig-zag path takes them past more foam. HOMs have been defined as any wave that doesn't make a direct path, I don't think that is in contention. It must include diffraction artefacts as the region of interest behaves as an independent source and hence the wayward energy radiates in all directions from there.
The second likely benefit is as you say the mouth related resonance. I believe this might be both width and length related.
The second likely benefit is as you say the mouth related resonance. I believe this might be both width and length related.
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