[Milsurplus] X-Ray Damage.. more

[J Forster]

Bob Camp wrote:

> Hi
>
> I must have missed the first post in the thread. The fact that they
> are microphones was something I missed.

Yup. The thread started with a post about known good, commercial (Sure)
crystal mikes that tested good being zapped during shipment.

> A lot of microphone elements are parabolic in their force to
> electricity characteristic. At "zero" they do not produce a useful
> response. To make them work you "polarize" the element with a high
> voltage. It's  a one time process, and normally heat is also involved.
> Sounds like yours got a bit to much ....

Crystal mikes are NOT electret mikes. The crystal is cut with a wet string
saw from a crystal. There is no 'polarization' process and certainly not
during shipment.

Best,
-John

>
>
> I'm a little surprised that they do the polarization after mount
> though. I alway assumed they did it to the bulk material .....
>
> Bob