Microphones and miking techniques - Condenser microphones

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This kind of microphone, also known as electrostatic, has a condenser inside it [Capacitor ] . One of the condenser's two plates is the microphone's diaphragm, which vibrates when the acoustic wave hits it. The plate's vibrations produces a variation in the distance between the two plates, therefore altering the capacity value. This implies a variation in voltage at the far ends of the plates, with a consequent flow of electric current. The diaphragm is made with mylar (a type of plastic) coated in a layer of gold (an excellent conductor). Initially it is necessary to apply some voltage in order to polarize the condenser. This voltage is called phantom power and is usually supplied by the mixer to which the microphone has been connected. More specifically, each of the mixer's channels has a button that triggers phantom power and sends a constant voltage of 48 V to the microphone.

The following diagrams illustrate how phantom power works: the first diagram displays its electric scheme, the second shows its logical scheme, the third the signal's graph, from which we understand that the signal gets amplified; this voltage amplification is necessary because the current that is generated by the microphone is very low and needs to be amplified before it arrives at the mixer's preamplification stage.

Microphones and miking techniques - Phantom power applied to a condenser microphone

Phantom power applied to a condenser microphone

So, phantom voltage has two aims: the first is to polarize the condenser inside the microphone, and the second is to amplify the current that issues from it. Condenser microphones are far more accurate than electrodynamic microphones because their diaphragm can be made out of very light material and can also be very small. Therefore they are extremely sensitive, even at higher frequencies.

The following is a short list of the main characteristics of condenser microphones:

  • Very thin diaphragm which allows good reproduction even of higher frequencies.

  • Easily damaged if exposed to very high sound-pressure.

  • Very delicate, therefore not ideal for live performances. More suitable for recording studio work.


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