On Wed, 10 Oct 2007 19:31:37 -0700, Larry Jaques
wrote:

Don Foreman wrote:
(..)

Those 'ducers aren't good for this. They're either too pricey, too
wimpy or have very limited bandwidth.

Here's what I used:

http://www.electronicpartsforless.co...id=36&df id=1

If ya use a 555 or 556, it needs a simple power amp comprised of a
coupla transistors working from +/- 15 volts.

Freq response?

Not really meaningful. Transistors were switching, rise & fall of
probably a microsecond or two. No problem producing a squarewave up
to 40 KHz. A 47-ohm series resistor in conjunction with the
capacitance of the speaker rounded this off to a semblance of a sine
wave.