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: Absorption is not diffusion/diffractionPosted by rowuk on: 11/24/2012

Hi BE,
we may not be in disagreement at all. Sandpaper finish is not necessarily absorptive. I was more referring to popular HOM-treating methods like foam or using softer materials to build or coat the horn.

I still have my doubts about how a rough surface can work as the grain is so much smaller than even a quarter wavelength of any frequency that would be reproduced and the "speed" of sound when it runs into a wall is ZERO unless the wall is conductive (absorptive/resonant) at that frequency. If this "grain" is a factor, then micro millimeter changes in the horn SHAPE (like with a coat of anything) will change things even more. Maybe the effect you notice is due to the horn being "slightly" smaller than before the coating? Granted, improvements in sound cannot always be explained as we do not have infinite knowledge of all of the parameters at work.

My doubts are based on my "primitive" understanding of how sound waves move. the acoustic generator "vibrates" and the air molecules next to it vibrate and bump into the next molecules that vibrate, and so forth. The air molecules in front of the driver do not travel to our ears. Also the acoustic "pressure" in a horn is different than physical pressure like filling up a balloon with air. So, what are the air molecules next to the rougher surface doing differently? The distribution of the density of the sound wave? I do not know. In any case, as Romy notices his effect at lower volumes, is this causing a non-linearity in the playback based on amplitude?

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