On 1/9/2017 7:41 AM, mcp6453 wrote:
It's been a long time since I heard the explanation, but there is a ratio below which a foreground vocal will mask a
second microphone's pickup of that same vocal in the mix. The ratio of the amplitude is 1:3, as I recall. Can anyone
tell me what that effect (or law of physics or phenomenon) is called?
Are you really talking about masking (meaning you hear one and not the
other), or are you asking about the cancellation or partial reduction of
certain frequencies that results when mixing the signal from two mics
picking up the same source? This is usually called "phase cancellation."
The amplitude difference between the mics affects how deep the notches
in the combined frequency response are. A 3:1 difference in amplitude is
10 dB, which is usually enough so that the irregularities in the
frequency response isn't too bothersome. With only 10 dB difference,
you'll hear both vocals in both mics and you won't have objectionable
phase cancellation, but you might want to shoot for better isolation
than that to make mixing easier. If you have to use a lot of EQ on one
vocal, remember that you're adding that same EQ, at least a little, to
the other vocal. This can be significant if the two mics are panned
fairly far apart in a mix.
There's no magic number, just whatever works. If you think you're going
to have a problem, consider having both vocalists work together on a
single mic. You may have heard of the "three-to-one" rule. This says
that you won't have too much of a problem with phase cancellation if the
distance between two mics is three times the distance between the
distance to the source of the mic that's the most distant of the two.
For example, if your singers were both singing 3 inches from their mics,
you'd be safe if the mics were more than 9 inches apart, which isn't
much of a problem. But if they're singing 10 inches back from the mics,
the mics should be about a yard apart. And with a setup like that, there
will probably be other things going into the mics that you don't want.
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