February 28, 2018
A microphone is a transducer. A transducer is a device that converts one form of energy to another. In turn a microphone is used to transform acoustic energy (sound) in to electrical energy (the audio signal).
There are a variety of different microphone types. Each has it’s own place in a recording studio and a well-trained engineer or producer will know when and where to use them.
- The Dynamic Microphone – This is certainly the most common type of microphone. You see them on snare drums & guitar cabinets. The Shure SM57 is the most famous (or infamous) dynamic mic around. With dynamic mics a sound wave causes the movement of a thin metallic diaphragm that is attached to a coil of wire. When sound hits the diaphragm, the surface vibrates in response. The motion of the diaphragm couples directly to the coil, which moves back and forth in the field of the magnet. As the coil cuts through the lines of the magnetic force in the gap, a small electrical current is induced in the wire. Dynamic mics are incredibly reliable, rugged and reliable. Because of this, you see them a lot at venues and stages where strength is key – sometimes over fidelity as dynamic mics are not as full spectrum as condensers. But there are certainly many times one would need them in a studio. Never underestimate a dynamic mic.
- The Condenser Microphone – Next to dynamic the condenser is the most common type of microphone. Certainly this is true in a recording studio. A gold-coated plastic diaphragm is mounted above a conductive back plate, which is often made of gold-plated ceramic. The diaphragm and back plate, separated by a small volume of air, form an electrical component called a capacitor (or condenser). A voltage (usually 48v or called phantom power) is applied to the diaphragm (usually in a preamp), charging it with a fixed, static voltage. When the diaphragm vibrates in response to a sound, it moves closer to and farther from the back plate. As it does so, the electrical charge that it induces in the back plate changes proportionally. The fluctuating voltage on the back plate is therefore an electrical representation of the diaphragm motion. Condensers tend to be a little more accurate, respond more quickly than dynamics and certainly have more top end than dynamic or ribbon mics.
- The Ribbon Microphone – Ribbon microphones use a method that is similar to that of dynamics. A very light, thin and sometimes fragile, corrugated metal ribbon is stretched within the air gap of a powerful magnet. The ribbon is clamped at the ends, but is free to move throughout its length. When sound strikes the ribbon, the ribbon vibrates in response. As is the case with the dynamic coil element, the moving ribbon cuts the magnetic lines of force in the air gap, and a voltage is thereby induced in the ribbon. Early ribbon microphones were insanely fragile. The ribbon could be damaged simply by blowing or coughing into the microphone. Ribbon mics have excellent sonic characteristics, with great warmth and gentle high frequency response. They also have excellent transient response and very low self-noise. For these reasons, some ribbon mics are prized as vocal and guitar microphones.
- There are a few other kinds of microphones. A carbon mic is one of the earliest microphone elements ever developed. However they aren’t really used much these days (they were used in wired telephones and telecommunications back int the day) and aren’t super desirable unless you are going for that specific effect. There are also crystal mics. They use the phenomenon of piezoelectricity which is the ability of materials to produce a voltage when subjected to pressure. It converts vibrations into an electrical signal. Piezoelectric crystal mics are often used as contact microphones to amplify sound from acoustic instruments, to sense drum hits/triggers, for electronic samples and to record sound in undesirable environments, such as underwater under high pressure.
There are many types of mics to use in a studio. Hiring engineers and producers who know which mic to use in each circumstance is an invaluable skill to have. You should think about that when choosing a studio and/or engineer.