Position Omni's for Boundary Effect?

[Bob Singleton]

Is it possible to position an omni mic like an Earthworks or Behringer
or similar shape, with a standard mic stand, close enough to a wall or
window to create boundary effect similar to a PZM? Is the gap between
the surface and the element so critical that the idea is impractical,
or could one simply put 10 sheets of paper (or something like that)
between the surface and the mic, then remove it to create the
appropriate gap?

Spending way too much time thinking about microphones...

Bob Singleton
Singleton Productions, Inc.
http://singletonproductions.com

[ScotFraser]

<< Is it possible to position an omni mic like an Earthworks or Behringer
or similar shape, with a standard mic stand, close enough to a wall or
window to create boundary effect similar to a PZM?>>

Yes, that's all a boundary mic is.

<< Is the gap between
the surface and the element so critical that the idea is impractical,
or could one simply put 10 sheets of paper (or something like that)
between the surface and the mic, then remove it to create the
appropriate gap?>>

The distance between the diaphragm & the boundary needs to be within the
"pressure zone" where the direct & reflected signal are in phase. The depth
varies with frequency, but I can't give you any specific dimensions. Remember
to take into account the depth that the diaphragm is recessed behind the grill.
The Crown PZMs left the diaphragm exposed, facing directly into the boundary.
Scott Fraser

[JoVee]

in article , Bob Singleton at
wrote on 8/9/04 7:29 PM:

> Is it possible to position an omni mic like an Earthworks or Behringer
> or similar shape, with a standard mic stand, close enough to a wall or
> window to create boundary effect similar to a PZM? Is the gap between
> the surface and the element so critical that the idea is impractical,
> or could one simply put 10 sheets of paper (or something like that)
> between the surface and the mic, then remove it to create the
> appropriate gap?
>
> Spending way too much time thinking about microphones...

lay the mic on its side, on the surface

if indeed you want to position the element looking AT the surface, the gap
needs to corespond to a wavelength above audibility.

[Scott Dorsey]

JoVee > wrote:
>
>lay the mic on its side, on the surface

EV used to sell a foam thing called the "Microphone Mouse" for doing just
that.

>if indeed you want to position the element looking AT the surface, the gap
>needs to corespond to a wavelength above audibility.

The trick that Crown patented was that they used the gap distance to create
a rising top octave which in turn compensated for the top octave falloff on
the capsules they used. You can do something similar on an EV 635A with
some gaffer tape and actually get some top end on the thing, but you will
have to remove the windscreen to get the diaphragm close enough to the
surface.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Arny Krueger]

"Bob Singleton" > wrote in message
om
> Is it possible to position an omni mic like an Earthworks or Behringer
> or similar shape, with a standard mic stand, close enough to a wall or
> window to create boundary effect similar to a PZM? Is the gap between
> the surface and the element so critical that the idea is impractical,
> or could one simply put 10 sheets of paper (or something like that)
> between the surface and the mic, then remove it to create the
> appropriate gap?

The Berhinger ECM 8000 looks like a bad candidate, because the capsule is
really a 1/4 capsule in a 1/2" casting, so there's a built-in 1/8" gap.

OTOH, the PZM effect doesn't just go completely away if your spacing is too
wide, or is the mic isn't an omni.

For example, sometimes just placing a mic on the floor, or on a table in the
right place will get you a really good recording.

[Mike Rivers]

In article > writes:

> << Is it possible to position an omni mic like an Earthworks or Behringer
> or similar shape, with a standard mic stand, close enough to a wall or
> window to create boundary effect similar to a PZM?>>

> The distance between the diaphragm & the boundary needs to be within the
> "pressure zone" where the direct & reflected signal are in phase. The depth
> varies with frequency, but I can't give you any specific dimensions.

Ed Long's original hand-made mics used a dollar bill to space the
capsule housing from the plate.

I've seen people "fake" boundary mics for dancers by pointing SM57s
downward just far off the stage so they didn't bang. Sometimes they
did. The dancers seemed to like it. (when the mics hit the stage, that
is)



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