Try using a Motorola Peizo Tweeter. I think some are spec'd into
ultrasonic range.

Highland Ham wrote:

Do you know of any freq response curves on the web for the garden
variety electrets? I've looked and haven't found any.

====================
I found an Archer packaged (for Tandy) cat no 270-092B Electret
Condenser Mike Element in its original Package, complete with response
curve.
From 30 - 3000 Hz the response is flat.
From 3000 Hz to 5000 Hz the response increases by approx 10 dB.
From 5000 - 9000 Hz the response drops such that it is back to its
original level at 9000 Hz .Above that freq the response drops.
Response curve is not extended beyond 12000 Hz



Frank GM0CSZ / KN6WH


--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

"Follow The Money" ;-P