On Thu, 28 Oct 2004 20:56:02 GMT, "Fleetie"
wrote:

I noticed with both my old Mission 752Fs, and now my jizzmatic Dynaudios,
that the position for optimum treble for each ear is _extremely_ narrow;
something like +/- 1cm laterally.

It seems not so easy to check vertically, but logically, I think the
situation ought to be the same.

And we're not talking big radiators here; in both cases, the tweeters
are about 2cm - 2.5cm diameter.

I'm always fidgeting to get the clearest, optimum treble. I move slowly
sideways, and suddenly one ear will "click" into a position of very clear,
perfect treble. The trick is to have them both so satisifed at the same
position, and it's _not_ easy!

(The effect arises from the radiation pattern you get when you plot
response versus angle from axis for high frequencies. There's a main
centre lobe which gets narrower as f increases. It also gets narrower
as the diameter of the radiator increases. So it's generally better
to have a smaller diameter tweeter to get a wider main lobe. If my
hazy memories of my acoustics degree serve me correctly.)

It's a pain, though.

Anyone else noticed this ultra-narrow-sweet-spot for high treble with
normal tweeters?

I think you'll find that it has nothing whatever to do with the
tweeters, it's just a sign of a *good* speaker. I have always noted
that when you have really top-class speakers in a good environment,
the image 'snaps' into sharpest focus on the exact midpoint of the the
speaker position bisector. Moving your head sideways by an inch makes
a significant difference. IME, if you have a big 'sweet spot', that's
because it's fuzzy *everywhere*.
--

Stewart Pinkerton | Music is Art - Audio is Engineering