Greetings,
I am building a 21" parabolic microphone. I have a prototype built and plan=
to purchase a EM172 mic capsule for it. Right now it is using a Radio Shac=
k capsule (very hissy) that I have from the very first mic I made about a d=
ecade ago. It works great as far as it goes. The question is, does it make =
any sense to use two capsules, one at the focal point facing the dish, and =
one facing away from the dish, pointing at the sound source?
The problem is that many of my sound sources (e.g. grey seals) vocalize at =
around 500 Hz, which I understand to be a weak spot in the parabola's respo=
nse curve. The parabola still seems advantageous to me in improving the dir=
ectionality over my shotgun (me66), but it seems from my tests that the me6=
6 is better than the parabola at picking up those 500 Hz sounds (played on =
my computer and positioned across the yard).
If I place a second capsule at the tip of the mic holder on the dish and wi=
re it in parallel with the focal point capsule, will I get the best of both=
, or just muddy the picture with strange phase differences? Or would it be =
better to wire the two mics into separate channels and then pick the better=
of the two later? Or is the parabola simply the wrong tool for these low f=
requencies?
I normally can't get too close to the seals when they are vocalizing: somet=
imes they are a mile distant, which is why I started down the parabola road=
, but that was before I learned about the poor response of parabolas at low=
frequencies.
Many thanks. This list has been hugely helpful to me in recent months as I =
attempt to actually understand what I have been bumbling around with for th=
e past several years.
John
John L Crockett
Westminster, Vermont
Let us live in harmony with the Earth
and all creatures
that our lives may be a blessing.
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