> One gets a 6 dB signal gain from the adding the output of the two capsule=
s together, but the capsule self-noise which is uncorrelated will only incr=
ease by 3 dB. So the net result is a signal to noise gain of about 3 dB for=
a two-capsule vs. one-capsule mic channel.
Gregory,
I was going to reply with those figures, but on second thoughts, the
coherent wanted signal should be identical from both capsules and therefore=
will not be 6db higher when directly connected. The combined impedance will=
be lower and, with a redesigned preamp, there may be a marginal improvement=
in s/n.
How far could this ne taken? What about a cluster of 7 capsules? The
problems I foresee would be a more directional pickup, and with all mics,
there is a practical tradeoff between diaphragm size and noise.
The claimed quietest mic - a test mic made by B&K - has a large diameter
diaphragm but is unsuitable for general audio use. With any mic, the therma=
l
noise of the air acts on both sides of the diaphragm, so the ultimate
theoretical limit would be 3db.
David Brinicombe
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