All:
I finally got the chance to test the Knowles HC-3 military microphone element I
ordered. The eBay seller claimed that it had the same frequency response as the
vintage Heil HC-5 and it is very close in that respect. However, it's not
nearly as sensitive as the Heil HC-5 so it requires A LOT more mic gain.
It also needs to be close-talked to the point where you're lips touch the
element screen. Move 1/2 inch away from the mic and the audio drops off to
nothing. The Heil HC-5/4 I have were also made to be close-talked, but they
have enough sensitivity so you can be 2 or 3 inches from the element and still
maintain good output.
I asked Bob Heil about all this and he said Knowles built the HC-3 for him
which eventually morphed into the original HC-4 and HC-5. He also mentioned
that a pre-amp could be used with the HC-3 to make it work.
So the $40 dollar military surplus HC-3 has the same high articulation as the
HC-5, but it lacks sensitive. I should also mention that the HC-3 is larger by
a 1/4 inch give or take so it's not a drop in replacement for Heil headsets
like the BM-10.
Tony -K2MO
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