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(Karl Winkler) wrote in message . com...
"greggery peccary" .@. wrote in message ...
hey out there, i'm in an audio production class and the instructor avoids a
direct answer to this question: is there something in the nature of a
slightly out of phase recording (such as that created by a difference in mic
distance) that can make something sound "warmer" like analog? i know all
about the "if it sounds good do it" philosophy, but i'm wondering to what
extent do engineers delve into phase corrction with their software? thanks
-greg

There is certainly a different sound when using a coincident pair of
mics vs. a spaced pair of mics, even if the exact same pair of mics is
used in the same room on the same acoustic source. The difference is
due to TOA (time of arrival) differences, but is this phase difference
is not constant with all frequencies or all parts of the source.
Imagine that a flute sitting to the front left of a spaced microphone
array, playing a melody. The sound from that flute arrives at the left
microphone first, then the one on the right. So there is a TOA
difference between the two outputs of the mic. However, the *phase*
difference varies with frequency, since phase is a sine *angle* issue.
In other words, the higher frequencies are more "out of phase" than
the lower frequencies (i.e. a greater angle of phase displacement).

For this situation, you actually could adjust the TOA between the two
signals by delaying the signal from the left microphone to match the
signal from the one on the right.

Even if you delay the signal from the left microphone to adjust for
TOA, there will be phase differences between the microphones - it
doesn't matter that there is only one source. Delaying one signal can
work for one frequency (or rather a few mathmatically related
frequencies), but not for a melody - there will be some frequencies
that will be 180 degrees out and will cancel if the mics are summed.
Because the waves of different frequencies have different physical
lengths and peak at different intervals, the phase relationships (what
point in it's phase curve each of the frequencies is when it arrives
at the mic related to what point other frequencies are in theirs) are
different in two mics at different distances from the source,
regardless of TOA.