Hello, I notice many compression drivers have a diffraction grating at their opening just past the diffraction plug.
I am wondering what effect this has on the sound.
Also, how does this effect spherical vs. planer wave fronts wrt OS waveguides?
I am wondering what effect this has on the sound.
Also, how does this effect spherical vs. planer wave fronts wrt OS waveguides?
I think you're describing the bug screen- it's not there for acoustic performance but to keep junk out of the compression chamber/gap. I removed mine in JBL 2426 and found them somewhat more transparent, but the big gain was when I added reticulated foam in the throat a la geddes.
Yes, I am describing the bug screen.
It is a diffraction grating and will effect the sound.
I am curious especially since Mr. Geddes says that the wave front is critical.
AFAIK, Geddes recommended removing the screens so that you could add material to fill the tiny gap where it joins to the waveguide, not because the screen itself affected the wavefront.
Even for 20kHz, the wavelength of a sound wave will be roughly 2cm. As the typical structure size of the bug screen will be about 1mm or 1/20 lambda, I would expect only very weak, if any diffraction effects.
Rundmaus
Not sure why you asked the question since you already appear to know the answer.
These screens aren't intended as diffraction gratings. Since there is a periodic nature to their weaving then there is some theoretical possibility that they create some wavelength diffraction, but if you look at the dimensions involved and the wavelengths radiated by a compression driver, then it is obvious that they would have no practical effect at audible frequencies.
David S
Edit: Ditto what he said.^^^
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