Put very approximately, you seem to get a half-power beamwidth of the order
of 45-90 deg across when the wavelength is similar to the diameter.

Hmm! 45-90 is a bit of a range. So diameter~=25mm, c~=344m/s, so
f~=13.7kHz.

I'm surprised. I'd have thought at that kind of frequency, the central
lobe would be considerably narrower, but I can't contradict you at the
moment.

That seems not to explain the extremely noticeable "micro-beaming" effect,
but maybe there are other things coming into play. I mean as I said, the
"sweet spot" is 1 or 2 cm at about 3 or 4 metres from the tweeter, which
is considerably less than ONE degree.

Thanks, anyway.


Martin
--
M.A.Poyser Tel.: 07967 110890
Manchester, U.K. http://www.fleetie.demon.co.uk