GoodSoundClub - Romy the Cat's Audio Site

In the Forum: Horn-Loaded Speakers
In the Thread: Battling stupid Horn Criticism as a concept

Post Subject: The vortexes are additional out of band noise................Posted by rowuk on: 11/25/2012

Hi Be,
the thread is about the "bad" reputation horns have with "audio" people. Applying liquid dynamics gives them more fuel for the fire, that is why I avoid using stuff that really doesn't apply. We have no real flow of air or "turbulence" in a horn (it is not a bass relex port.....). We have diffraction - especially when the contour has edges like with early CD designs or when the horn is of improper design or used in the wrong band. Earl Geddes also has written about the horn throat-compression driver transition and he uses clay to make it perfectly smooth. Without the clay, he claims to have measured additional audible HOM artifacts. In fact, he uses foam in the "waveguide" to correct for these HOM. This to me means that the horn in his case is not properly designed and that the sound "wants" to do something else much different than the horn thus creating artifacts. I think that there are horn shapes that have more "problems" than others. Clay is probably a great idea though to make sure that the horn/driver transition is free of a stepped contour. http://www.diyaudio.com/forums/gedlee/122318-diy-waveguide-loudspeaker-kit-112.html post 1112

If foam or sandpaper help with a particular design, then I guess all that counts is what comes out of the front. I just have no explanation that fits with the physics that I have learned. That should never slow someone else down though. Again, if something the size of sandpaper grains makes such a big difference, then so does a coat of paint thick enough to hold the grains. Sandpaper regardless of how thin changes the dimensions of the mouth of a compression driver in a very big way - at one of the most sensitive parts of the whole system. That will change response strictly based on decreased size/volume. The binder for the grains (paint/glue) also "damps" the surface of the horn. This also could make a big difference - with or without sand.

I do not doubt that there is a "difference" in sound with any treatment that we apply to anything audio. Trumpets sound different when they are lacquered too (When they are gold or silver plated however, I have never noticed a difference). I have never added sand to the lacquer however. I will try this sometime.

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