I have some speaker systems and I want to test their frequency
response. 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.

Then I take my mic and place it close to a speaker, 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.

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

I did this with two different speaker sets and you can see the
results below:

http://img224.echo.cx/my.php?image=t...esponse7xo.png
http://img224.echo.cx/my.php?image=o...esponse8hv.png

Original test file (downloaded recording):

http://img156.echo.cx/my.php?image=testclip7ci.png

Is this lousy frequency response or what? Am I doing something
wrong with my testing method?