how can I make a test for how far off they are?
I know I read at one time how but after doing a search I don't find anything
thanks for your help
I have not done this but I think the following should work:
1) Hook up your laptop rig with just 1 mic connected. Likewise just hook up 1 speaker out of your stereo system. Place mic in front of this speaker.
2) play test tones at a variety of frequencies. I would set the combination of playback volume and preamp level to be peaking at ~-5 dB to allow headroom for frequency response anomalies in speakers and mics while attaining max possible dynamic range for your measurement. I would crank the volume to a point where you do not have to max your pre out to get decent levels, if possible. Also make sure the speakers are not so loud they are distorting.
Write down what the peak levels are at the different frequencies.
3) repeat with the other mic. Make sure positioning is EXACTLY the same as for the 1st mic.
4) compare the two measurements.
I am not sure if this measurement is sensitive enough to detect very small differences in mic sensitivity, though I would think anything over a dB or so would show up.
Alternatively you could hook up both mics and place them side by side, make sure they are symmetric with respect to the drivers of your speakers. Then you can measure both at the same time. I think it is very important to make sure both mics are seeing the same volume from the speaker, which is why the geometry of how you set up the mics with respect to one another and the speaker is critical.
Anyone else have other suggestions?
Good luck,
Ben