Originally posted by Harvey Gerst
Mics are quirky pieces of equipment. No manufacturer can guarantee absolute consistency for every mic, so they have a "window of acceptance", whereby any mic that can pass thru that window is considered "good" and anything that doesn't fit inside the window is rejected.
Imagine a 3 foot by 3 foot window, wide open, and you can see that a 35" circle would pass thru the window, but so would a 35" by 35" square. Both go thru the window, but they are certainly different from each other.
Humidity, machine adjustments, thickness variations, component tolerances, and even the mood of the assembler that day all play a part in determining the consistency and final sound of any one single mic. The differences we hear between "identical models" of a microphone can be broken down as follows:
1. Self noise
2. Frequency response
3. Sensitivity
In actual order of importance for matching, it would look like this:
1. Frequency response
2. Self noise
3. Sensitivity
Usually self noise can be separated into 3 broad categories:
1. Higher than normal
2. Normal
3. Lower than normal
After a manufacturer has broken the mics up into these three categories, they try to match the frequency response. That breaks down into about 5 categories:
1. Neutral
2. Slight bass boost
3. Slight treble boost
4. Slight mid boost
5. Slight treble AND bass boost.
What about dips? Well, a slight bass boost is close to the sound of a slight treble cut, so they sound pretty similar. A cut mid sounds similar to a slight treble and bass boost. Anyway, that gets the mics split up into 15 general categories.
They then look for mics in each pile with similar sensitivities, and they wind up with a bunch of matched pairs.
Now of course, the "matched pair that YOU would like to get would have low noise, neutral frequency response, and high sensitivity, but that's not the definition of a "matched pair" - it's a definition of the best "matched pair" in that particular batch.
