Still no help, I'm afraid...

I am surprised that LF crystals are all that different from the ones in the
MHz.  Although they get quite large (physically) at these low frequencies.

You seem to have a good handle on the situation.  The high Q does exactly
what you say.  The way I've seen crystals used to get a "bandpass" is to
combine several of them that have been cut (or altered) to slightly
different frequencies.  I can't help you with "how".   You could also lower
the Q (probably throwing away some of the other good characteristics that
made you choose the crystal in the first place).   And then of course, I
could do the traditional PICList thing and tell you to do it a different
way--which at these frequencies, I would certainly consider.  I suspect this
isn't the first thing you've tried.

As far as it being sensitive to mechanical input...well, what you have there
is a piezoelectric microphone, after all.

Barry
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