Topic: Mic 3D Patterns

[RobertNC]

I'm trying visualize mic polar patterns in 3 dimensions to maybe? better understand things like crowd and ceiling proximity effects.  I realize that the physical/electrical construction means the true pattern is going to be perturbed from shadow effects etc.  But let's assume "perfect" polar patterns in this discussion, i.e hypothetical element with no body tube, approaching zero dimensions etc etc etc.

So in this perfect case would an omni pattern be represented by a perfect symettrical sphere?

And of more interest to me, would a Figure 8 for example be a pair of symmetrical lobes in 3D?

I've attached an image that conveys what I mean.  (I know, not exactly the shape of the polar pattern of a Figure 8, I scarfed a p-orbital model photo from a chem site, but it conveys the sense of 3D - You get the idea).  

[DSatz]

RobertNC, yes, you have the idea all right--directional patterns are three-dimensional, and in their ideal forms they are rotationally symmetrical. See the attached examples from a BeyerDynamic catalog which try to represent this fact.

In reality there can be quite a difference between the polar pattern in the horizontal (lateral) plane and in the vertical plane, depending on the design and shape of a microphone and its capsule. One extreme example of this is a microphone from Microtech Gefell which has an extremely narrow pickup pattern in the vertical plane but a more conventional directionality in the horizontal plane. Some Milab condensers have rectangular capsules, which have distinctly narrower vertical directional patterns than their horizontal directional patterns.

But some degree of difference is usually present in more conventional designs as well, since with a conventional, cylindrical "front address" microphone the sound field "sees" a different shape at 0 degrees than at other angles, while with a cylindrical "side address" microphone the physical shape is the same for all angles of incidence within the horizontal plane.

--best regards

[Petrus]

Patterns are rotationaly symmetrical if the mic capsule is round or square. Like  DStz says there are some odd shaped mics out there, one example is Pearl ELM series, very large, tall capsules (1:7 ratio) which makes them reject ceiling and floor reflections. Interesting.

http://www.pearl.se/estart.htm

[Jammin72]

Patterns are rotationaly symmetrical if the mic capsule is round or square. Like  DStz says there are some odd shaped mics out there, one example is Pearl ELM series, very large, tall capsules (1:7 ratio) which makes them reject ceiling and floor reflections. Interesting.

http://www.pearl.se/estart.htm

I would think this to be a benefit to the FOB, head-height tapers.  Rake the angle of the mics about 30 deg to get the pattern up in the air with a diminished reflection from the floor, could really clean up some of those  recordings.  Of course I've never heard a Pearl mic so....

[RobertNC]

thanks +ts