Moving Coil Frequency Response

In order to achieve flat frequency response the moving coil microphone has the following characteristics:

1.	the diaphragm's main resonance is placed within the middle of the audio response range - this resonance is not noticed at the output as a coloration of the signal (which would defeat the purpose of designing for a flat frequency response) because of...
2.	additional resonators in the form of slots, holes, air passages and trapped air spaces which also act on the diaphragm - these correct the frequency response curve irregularities and also extend the frequency response toward the upper and lower ends of the audio spectrum

This graphic shows an example frequency response curve of a hypothetical moving coil microphone. (1) is the damped resonance of the vibrating system - the diaphragm, voice coil, damping ring and flux field. (2), (3) and (4) are additional resonances which add to and overlap both the main resonance and each other and thereby contribute to a flatter frequency response over the microphone's total range. Note that (1) peaks at about 150Hz.