John,
An excellent account of how an M-S image is formed.
> All arrays distort the image in one way or another, so I am not
> discounting super-cardiod MS as useful technique for stereo nature
> recording - though be extra careful with any content outside the
> angle of focus.
Polar diagrams are normally only given in two dimensions and sources
above or below the given horizontal plane have very different
object/image relationships. I think this is the major problem with
three dimesional wildlife recording, and not forgetting ground
reflections.
My experience is that an M-S setup gives a cleaner front image, along
with an easy adjustment of the image in post-production, but the
off-axis noise is a problem. A super-cardioid as the M component is
equivalent to an omni plus a forward facing fig-8. Tracking all three
components through a 360 degree three dimensional solid angle reveals
the overall noise pickup as in a natural or reverberant environment.
What a cardioid or supercardioid gives is a chance to create a low
sensitivity rear area or a rear band with a top and bottom "bulge" at
a lower sensitivity. If you are lucky, you can aim the rig to minimise
an unwanted source risking compromising the ideal stereo object source
angles.
David
David Brinicombe
North Devon, UK
Cogito cogito ergo cogito sum - Ambrose Bierce
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