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The Sucking Sound of Tarps over Speakers

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Art Welter:
Testing a new HF horn today, occurred to me that I had never actually seen what plastic sheet does to sound when placed over a speaker, though I have heard how bad it can sound.

Having done hundreds of outdoor shows with tarps or plastic sheet over the speakers for extended periods of time, it was obvious that the HF was reduced, but not as obvious how bad the comb filtering was.

A "tarp EQ"of a 6-10 dB HF shelf boost helps correct the general downhill trend, but no way can the comb filtering be corrected, explaining the nasty sound.

The thicker the plastic, the worse the effect.
The depth of the HF horn will also affect the location of the dips.
The white line is with no plastic, the light blue is a 1.1 mil thick garbage bag, the orange is around 5 mil thick.


Art Welter

Moby (Mike Diack):
Interesting...apart from the response issue, If you use a tight garbage bag you end up with the worlds biggest kazoo. There must be something that lets noise through but not wetness.

TJ (Tom) Cornish:
I sense a market for a new recording plugin:

Outdoor Festival - Transforms your music from the boring pristine-ness of standard recording techniques to the dynamic, warm (dry?) live outdoor concert sound we all crave.

There should also be an app for that, so I can play my ITunes library through this filter.

P.S. - Version 2 forthcoming - will include Gunness De-Focusing

James Feenstra:
what about the effect of a blow through or scrim?

Geoff Doane:
Art Welter wrote on Tue, 18 January 2011 02:04
, it was obvious that the HF was reduced, but not as obvious how bad the comb filtering was.

That's what a tester found back in the '80s when he wanted to know what the popular "tissue paper over the tweeters" of studio monitors was really doing to the sound of the speakers.  The tissue paper didn't really reduce the overall level very much, but did create serious comb filtering.

Why it was a desirable technique is anybody's guess.



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