"Carl Valle" wrote in message
m
"Arny Krueger" wrote in message
...
wrote in message

oups.com


It sounds like it would be much easier if you were back
in
the
70's, with all those spectrum analyzers that were
available
back then.

Just because they aren't in the same form as they were
then,
doesn't mean that they don't exist.

They came with a mic, and with pink noise or warble
tones,
you
could get a rough look at what your looking for.

Modern stuff does more and has far higher resolution.
Much
of it is computer-based.

You won't need much resolution since the damn speakers
have no
midrange or treble.

That makes no sense at all. If speakers have response
problems, we need our ears and our test equipment to
determine what the problem is. Bad speakers aren't a
justification for having poor test equipment.

I can get pretty good generalized response curves off my
old
Audio Control and its cheap measurement mic.

You get something, but how accurate is it?

Here's an independent critical look at the Audio Control
RTA:

http://www.hometheaterhifi.com/volum...equalizer.html

"For one thing, a simple spectrum analyzer cannot capture
information in the time domain, and therefore cannot
differentiate between direct sound and reflected sound. So,
what the spectrum analyzer shows is the average of the two.
Because of this, if adjusted solely by the RTA, an EQ alters
both the direct and indirect sound so that the two sum flat,
although neither may be so individually. Human hearing works
in a much more complex manner, so that although we may not
hear the two (direct and indirect sound) as distinctly
separate in most home environments, altering one to correct
the other won't always work very well. One of the best
examples of this is to get a dipolar speaker, which usually
has a horrible pink noise response due to a high ratio of
delayed, reflected sound from the rear wall.

"If you adjust an EQ to compensate for the RTA reading, you
often get sliders shoved all over the place, and a very
weird tonality. This is because the process of hearing
somewhat compensates for the environment, and takes much of
the comb filtering effects of reflected/direct sound
interaction which skew the tonality of continuous pink
noise, and puts it to use with impulsive signals to derive
spatial cues about the environment. That's why
bipolar/dipolar speakers tend to do such a great job
providing a "they are here" presentation. Tangent aside,
even though an equalizer can slightly compensate for room
problems, if the room's broken, you're best off fixing the
room.

"Secondly, a spectrum analyzer, especially a 10 band, 1
octave jobbie, has limited frequency resolution, looking
only across relatively broad sections. For instance, the
frequency response may vary 10 dB up and down, but so long
as it averages within that octave, appears perfectly flat on
the analyzer. The corollary is that an equalizer with
similar resolution cannot effectively compensate for narrow
band response peaks or dips caused either by loudspeaker
problems or extreme room modes.


As far as the anechoic chamber, that is not actually
required. You can make
measurements in the back yard and get fairly good
cures for speaker design problems such as box tuning and
beaming. its a good way to measure free air resonance
also.

Actually, a RTA is a very poor means for measuring woofer
free air resonance. A signal generator a resistor and a AC
voltmeter are the classic means which yields excellent
results. Since I have a highly accurate computer-based
speaker impedance-measuring facility, that's what I use.

The technology of acoustic measurements has made dramatic
improvements in performance and convenience in the last 5-10
years. The key component has been the computer with an
apporpriate audio interface.