Let´s talk about microphones.

This page will only cover the most common types used in music production and recording. (PZM microphones will be included in another page )

Soon, I will be writing more arcticles regarding many other aspects on this subject, and many more ( I hope ) about practical aproaches and in dept studio procedures, but for now let´s start with the basics and get into the principles of operation.

A microphone is an acoustic to electric transducer that converts energy from one form to another - acoustic energy ( sound waves ) into electric energy ( audio signal ). Different types of microphone have different ways of converting energy, but they all share one common thing: the diaphragm, this is a thin and light material which vibrates in response to sound pressure generating electrical current.

So, the main difference between microphones, is the type of diaphragm and how it generates the electrical signal.

Condenser means Capacitator, an electronic component which stores energy in the form of an electrostatic field.

A capacitator has two plates with energy/voltage stored between them, one of the plates is extremely light and acts as the diaphragm, the other plate, known as back-plate, remains static.

When the diaphragm vibrates in response to sound waves, the distance between the two plates will change and therefore changing the capacitance.

when the plates are closer, capacitance is increased and a charge current occurs, when the plates are further apart, capacitance decreases resulting in a current discharge.

For this to work, voltage is required across the capacitator, this is supplied by a battery or by an external source - phantom power (+48V)

because condenser elements produces a signal voltage with almost no power, they need to incorporate an amplifier driving the microphone line and boosting the signal level. Early condenser mics used tube amplifiers, resulting in a larger body. Today, transistor based amps are most common and the mics became physically smaller.

condenser microphones are usually less rugged than moving-coil dynamic mics, they are more sensitive to physical shocks and environmental factors, like temperature changes and humidity.

Because the diaphragm of a condenser is not loaded with the mass of the coil, it can respond very quickly and accurately to an incident sound. Therefore, condensers, generally, have excellent sonic characteristics, being widely used in recording tasks . they´re not the best microphones for live performance in general. However, there are some models designed especially for live road work.

The dynamic microphone, uses the electromagnet principle, known as Faraday´s Law.

The principle states that when a conductor is moved through a magnetic field, electric current is induced in the conductor. In these microphones, the magnetic field is created by magnets, and the conductor is produced in two common types of arrangement: moving-coil or ribbon.

Moving-Coil Microphones

The conductor is made from a coil of wire ( usually cooper ), attached to the coil there´s a circular diaphragm, typically made from very light plastic materials or aluminum. When the diaphragm vibrates in response to sound waves, the coil moves past the magnet, creating electrical current in the conductor - the coil itself.

( A loudspeaker uses exactly the same process in reverse, this will perform the opposite function of the microphone by converting electrical energy into acoustic energy. )

These are the most common type of microphone in contemporary sound work. they are the most rugged and reliable, because of this, they are the most common in stage applications. They are also the most insensitive to enviromental factors, making them ideal for outdoor works.

Dynamic mics are also very popular in the recording studio, especialy for close micing aplicattions.

Ribbon Microphone

In this arrangement, the conductor is a thin corrugated metal plate (ribbon) stretched and suspended between magnets.

The ribbon responds to the air velocity of sound waves. The ribbon vibrates, breaking the magnetic field, producing a small electrical current. So, in this case, the diaphragm and the conductor are the same.

Voltage is very small and the impedance very low, so, all ribbon microphones incorporate a transformer, this will boost the signal voltage and also have the dual function of isolating the impedance from the load presented by the input to which the microphone is connected.

Ribbons are the most fragile of all mic types, the ribbon can be damaged simply by blowing into the microphone. So they are used primarily in recording studios.

These microphones are known by their gentle high frequency response, good transient reaction, great warmth and very low self noise

That's all for now folks, the next subject will cover microphone pickup patterns.

thanks for reading,

feel free to leave your comments or questions.