> My blimps are 45cm x 25 cm and 6 to 8 cm from the microphone
> capsules.
> Is it better to make bigger blimps and rounder? Or use fake fur with
> longer hair and thiker?
Jos=E9,
Yes, no.
Sharp corners will tend to create more turbulence which is why
commercial baskets are rounded. Size is important in maximising the
radius of curvature. It's to do with the Reynold's number - it's in
Wiki if you must. :-) It is not well written, but it boils down to the
bigger the better. I studied all this jazz 55 years ago. :-(
A blimp type windgag has a membrane on the grid, and another two
layers on the fluffy cover. All of these affect the frequency
response, especially off-axis, and you can hear this with a
before/after test.
Basically we are taking an expensive mic and ruining its directivity
and frequency response in order to make it useable in a wind. I's a
trade off between response and wind rejection, but the thinner the
combined layers are, the better.
I've never seen a full explanation of why a hairy layer helps, but my
take is that thin "fur" helps to smooth the flow of air over the whole
assembly. To avoid more top loss, this fluffy layer should be as loose
as possible and the problem with some "replacement" covers is to make
too thick a combined layer. As I keep saying, you can test the effect
of false fur or any membrane material by putting it over your head.
You should hear a bass cut but not muffled HF.
I've got more theory on this but that can wait. Suffice it to say that
any layer around a mic will alter its phase response, and more than
one layer will affect it more than once. The only real test is to
experiment and listen.
David
David Brinicombe
North Devon, UK
Cogito cogito ergo cogito sum - Ambrose Bierce
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