[HAM] Correctamunde: Single louver horn compartment damping material?

[David Anderson]

I think I can venture an answer to this question.

Speakers (and here I mean the drivers) direct sound energy in two directions, forwards and backwards. The potential problem with the sound coming from the back of the cone is that it can bounce off the back of the speaker enclosure and interact with the cone. Its effect on the cone depends on the phase angle of the reflection, which depends, in turn, on the wavelength. The practical result is that it may produce pronounced peaks and dips in the frequency response of the driver, depending on whether the reflections are interfering with or reinforcing the given signal. 

Reducing the reflections should smooth the frequency response of the driver, much as the cotton ball in the throat of the horn is there to decrease the Q of the horn and, thus, reduce the tendency of the horn to emphasize certain frequencies based on the natural resonance of the horn.

That's the theory at least. Whether or not the cabinet damping in the Leslie really works that well is another question. I guess if you really wanted to, you could sweep the woofer with a test signal both with and without damping in place to see if the response changed noticeably. I have read that intelligently applied damping can give the effective performance of a larger enclosure.

David A.

>Without having any actual facts at my disposal, my attitude has been that 
>they sound just fine without it, and why do anything at all to damp the 
>sound? It would be interesting to hear what Leslie's original intention was.