Thanks for adding the stuff on mixers, superb! I have a couple of things you could add to the microphones section:
To add to dynamic mics:
Dynamic mics work on the same principles as the moving coil loudspeaker, but backwards (makes it easier for some people to grasp the concept).
To add to capacitor mics:
The diaphragm of a condensor mic and its plate basically form a capacitor and when sound strikes the diaphragm, the distance between the diaphragm and other charged plate changes, which results in varying capacitance, resulting in a varying voltage being output by the mic which is the signal. Their upper frequency response extends much further than dynamic mics due to the fact that the diaphragm is of a much lower mass and therefore low-energy, high-frequency sound has a better chance of moving it.
Electret Microphones:
These work on the same principles of the condensor microphone but the diaphragm is made of a special material which is naturally charged and as a result does not need phantom power. This charge does gradualy depleet over time but modern electret mics will last 30 years plus.
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That's it for now but I'll write something about other microphone types (ribbon and piezo electric) and different polar patterns (omni, cardioid, hyper cardioid, figure of eight etc) with some stuff on micing techniques using combinations of them (mid-side, xy, etc)
Thanks again!
Regards,
Neil.