matching mics...

[evan]

Is there a better way to match microphones than by ear? I'll probably be getting a second C3000B, and am not sure how to go about finding one that sounds the closest.

[thunderboy]

By taste, maybe?

[evan]

I always did love the subtle bitterness of a gold-sputtered diaphragm...

[I'm Painting Again]

try setting the two mics up at the same angle and reversing phase one and see how well they cancel each other out..

[stapes]

There are several different ways to test for stereo matching of mics, and most get you pretty close to what you need for "stereo" applications. One of the more important aspects of matching mics is average sensitivity. That means basically both mics should be putting out the same amount of output on average across the frequency spectrum. If you're having to crank one pre amp a little bit more than the other, than you are adding that little bit of extra something that could cause the image to seem weird. Goes a long way with colored or noisey pre's, but not so much with cleaner stuff. The other important thing is to make sure there aren't any wild fluctuations in frequency response. Depending on your application, you may not notice a slight change in frequency response because once you get reflections and refractions of soundwaves hitting both mics, things will be different at each mic. Sometimes a little deviation in the frequency response will enhance the stereo image too. You just have to listen, though. If you're using stereo mics for, say, a string quartet, and the violin is postioned roughly center in the image, and goes up some scale, weird stuff could happen. As the violin goes into and out of the difference between the mics, the stereo image could appear to shift in that range. Could be cool for an effect, or just plain annoying to some audiophile.
Now to the testing procedures. Testing for sensitivity is easy. Just use an oscillator through the speakers and put the mic in a spot, and note where the output is on a VU meter from that mic. Then, put the other mic in the exact same place, and note the postition on the VU meter. If they're within a half to a quarter dB, you're gold. Be sure that YOU are in the exact same postion as well. The refractions and reflections of your body can cause a change in about 20 dB if you're not careful.
Testing frequency response is a little more subjective without access to an anechoic chamber. A friend of mine taught me a really neat trick that you can do at home, though. It's the same principle as the sensitivity, but you want to use a broad band sound source, like a cymbal or pink noise. Play back the source on the monitors while recording the output of the mic into a DAW. Then do the exact same thing with the other mic. Then zoom in on the waveform and highlight a section that is like 2 to 10 milliseconds. Put it on loop play, or just hit the space bar continually. You should just hear some kind of popping sound. Now compare the sound of the popping between the two. They should have slightly or totally different timbres depending on the difference in their frequency response. It's uncanny how such a small sliver of a sound can give you enough information about the frequency response. It works, but it's not rocket science.
By the way, this is not what we do to match the omni mics. Most mics are uniformly flat from 20 to 20, but we try to filter out the ones that aren't. Mostly the average sensitivity is what varies the most, and we bin them accordingly.

Hope this all helps,

Erik Wofford
Stapes Audio

[DeafinONEear]

to append to sky's post, what you want to do is take both mics and place them as close as possible, with one mic's phase flipped (if you don't have this availablitily on a board or portable preamp, keep one cord specifically for phase switching, switch pins 2 and 3 and label the cord so that you know which one it is). Subject them to a constant sound source and the mics that have the closest gain settings on your amp (pre, board, whatever) will have the closest match.
other than that, there's a couple of anaechoic chambers in the country you might be able to book for a couple thousand bucks...

[I'm Painting Again]

haha..

thanks for the backup..i'm verbally challanged righrt noww..

too much shnapps.