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Coincident techniques are the most popular type for stereo recording.
These are most often implemented using directional microphones vertically
aligned on a common axis and set at an angle to each other in the horizontal
plane.
The advantages this method offers are minimum phase differences
between the two capsules for sound sources lying within the horizontal plane.
Another is the angular accuracy of the stereo image not being affected by the
distance of the microphones from the sound source. All large diaphragm (1 inch
and larger) microphones should be used in this manner for satisfying results.
Some small diaphragm microphones , most notably the Schoeps Collette series,
suffer from a lack of "sense of space" utilizing this method, due to the
lack of interchannel delay time. The Microtech Geffel small diaphragm mics
do not exhibit this problem. Near coincident techniques are recommended for
microphones with these problems, where they can yield very good results.
The microphone polar patterns used for this can be anything between the
figure of eight to the sub cardioid pattern. The angle between the center
lines of the pickup patterns of the two microphones, or "included angle",
is determined by the polar pattern of the microphone, the position of the
sound source and the desired effect (i.e. how much room sound you want, the
width of image and the like). For the smoothest , widest image, the included
angle should be twice the value of the angle between the center line and
the -3db point on the polar pattern at 1khz. Poor acoustic conditions could
mandate a smaller included angle in order to reject undesirable components
or a microphone with a tighter polar pattern.
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