Pink_isn't_well wrote:
I have some speaker systems and I want to test their frequency
response.

Before we get into the specifics of your case, let me ask you,
in all seriousness, why do you want to do this? Let's assume
for the moment your methods are correct and your data is good.
What are you going to do with this data? How are you going to
act on it? That's real important in determining WHAT data you
need to get.

Do you want to know the frequency response becuas you're just
curious or because you need to make design changes? Very
different sorts of data are needed.

That being said, let's proceed...

I'm not a sound engineer or anything and I don't really
know much about audio. But I assumed I could do this in the
following way.

I found a test clip on the net which has several frequencies in the
audible range 20 Hz - 20 kHz, each playing for 2 seconds. I open it
in Nero Wave Editor and it shows that it has the same level from
start to finish.

First problem: "several frequencies." Do you mean stepped sine
waves? Narrow band pink noise? What? All of these have their
advantages and disadvantages and require appropriate techniques
to gather useful data.

Then I take my mic

Second problem, what kind of mic? This has a profound influence
over the usability of the results. For reliable results, just
any ol' microphone won't do. Different microphones that may be
suitable different vocal or musical applications are generally
highly unsuitable for measurement purposes.

and place it close to a speaker,

Third problem: depending upon what you mean by "close," your
results are going to be severely skewed by a number of proximity
effects that make such measurements suspect under a number of
conditions.

Fourth problem: under what acoustical conditions are you measuring?
The existance of noise plus the influence of nearby reflective
boundaries and room-reletaed resonance can have a tremendous
influsence over such measurements.

I mute the
other speaker and playback this file, recording with the
microphone. I then save the recording uncompressed and open it in
Nero Wave Editor to see how loud/quiet each frequency is.

Fifth problem: such a display yells you nothing about frequency
response. Assuming the data you recorded is useable, a linear
display of amplitude is next to useless. FOr example, take the
differenence beween the loudest possible signal and one half as
loud: that's 1/4 of the height of the graph and corresponds
to a level difference of 6db between those to levels. But that
smae 1/4 height difference could correspond to a difference
of 10 db, if it's netween 25% and 75%, or it could correspond
to a difference of 34 dB if that 1/4 height is between 1% and
51%!

My understanding is that the recording should be as close as
possible to the test file that I use as input.

No, not necessarily.

Is this lousy frequency response or what?

It's worse than that: it's a useless frequency response. Because
of all the problems outlined above, your data is invalid. This
is not to say your speakers do or do not have a bad frequency
response: it's just that there is no way of knowing that from
the data you're presented.

Am I doing something wrong with my testing method?

Yes, regrettably, just about everything fundamental is wrong
with your method.

Start first with answering my first question: why do you want to
do this?