The mics in a matched pair will both have similar frequency responses, and similar output for a given sound level, and similar self-noise etc. In other words, they will be selected for their similarities. This is quite important if they are to be used for accurate stereo recordings, but isn't so important if the mics aren't going to be used for stereo. You could get the same result by buying half a dozen (or 20 or 50 or 500) of a particular model of mic, and testing each one, and selecting two which are very similar, but think of how much effort that would involve. The better manufacturers test their mics extensively, and it's quite easy for them to match pairs/sets, thus providing a nice service to their customers (at a premium...)
- Wil
