From: Klas Strandberg <>
>
> Sorry, I'm sending the wrong postings to the wrong people here.
>
> An omni is a closed cylindrical can with a membrane as one of it's sides.=
> The pressure inside of it tends to be constant, and tend to keep the
> membrane still, not so much affected by wind. (Or movement - handling
> noise). The membrane moves because the pressure inside the can is compare=
d
> to the pressure outside of it.
>
> A directional mic is a tube, with a membrane as the only one side. Both
> sides of the membrane will get affected by wind, and there is no "constan=
t
> pressure" tending to hold the membrane still.
> Therefore a directional mic need a much better wind protection than an om=
ni
> and is also more sensitive to handling noise.
>
> Imagine a tin-can where you have removed one side and replaced it with a=
> piece of balloon-rubber. Imagine you blow on the rubber. It will not go s=
o
> much inwards, as the pressure inside the can will hold it where it is.
> Imagine you move it. The same thing will happen. The membrane will not mo=
ve
> much.
>
> Now imagine that you take a tube and place the same rubber over it and tr=
y
> the same experiments.
If you do so, put the closed one out in a snowbank, then after a while
observe the rubber, now bring it in and set it next to the fire, observe
the rubber again. Did you notice the change in this closed system? What
would happen to a mic capsule that behaved like this?
Omnis are not closed cans, they are vented too. Just not the same kind
of venting as directional.
> If both have excellent suspension and wind protection, you will not find=
> much difference.
And if they don't have excellent suspension and wind protection then you
won't be able to do much nature recording. Or at least be severely
limited as to when you can record.
Walt
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