On Mon, 16 May 2005 19:58:04 GMT, "Tim Martin"
wrote:


"Stewart Pinkerton" wrote in message
.. .

That's true, but unless you have access to good SPL measuring gear,
you may have some difficulty knowing where 'flat' is unless everything
is matched.

You don't need to be able to measure the SPL, just the signal generated by a
microphone.

Only if you know that the mic response is flat!

Take some frequency within the range of the bass and mid-range
speaker, feed a signal to the bass speaker, and measure the microphone
output. Now feed the frequency to the mid-range, and adjust its level until
the microphone is generating the same ouput.

Repeat for the mid-range and HF speakers.

You don't even need a calibrated microphone.

You do, if you want a flat response from your speakers. Also, note
that you need to be *very* careful, if you're measurements are not to
be swamped by room effects. You might even need to move into the
garden for this, with the mic suspended above the speaker, itself
several feet in the air and pointing upwards. And then you've got to
set up your angles and positioning properly to get your full family of
responses to calculate when you have a flat *power* response, rather
than just a flat axial response, or do you want a slightly falling
power response, and if so at what slope, etc etc.

Measuring speakers properly ain't rocket science, but it's
close...................
--

Stewart Pinkerton | Music is Art - Audio is Engineering