Microphone Types and How They Work
Over the last sixty years, microphones and microphone technology have changed quite dramatically. Ever wonder about the different types of microphones and how they can be used? If so, you’ve come to the right place.
What are Microphones?
Microphones capture sound waves in the air and turn them into identical electrical signals. To replicate the original audio, you can send the signals from the mic’s output to a mixer or audio interface for recording or to studio monitors, to convert them back into sound waves.
Each of the three primary types of microphones – dynamic microphones, condenser microphones, and ribbon microphones – has a different method for converting sound into electrical signals.
However, all three have the same core construction. The capsule, otherwise known as a baffle, picks up the sound and converts it to electrical energy. Inside the capsule is a diaphragm, a thin membrane that vibrates when it contacts sound waves, initiating the conversion process.
The ideal types of microphones for a given situation directly capture your intended audio source, such as your voice or a musical instrument, without picking up any other nearby sound. For example, a singer on stage needs a microphone that will capture their voice while minimizing the pickup of the instruments in the band.
The oldest type is the carbon microphone. The carbon microphone uses a capsule with carbon granules pressed between two metal plates. The sound vibrations cause one of the thin metal plates to vibrate and presses the carbon granules together.
This will cause a change in resistance between the two metal plates. A disadvantage is that there is always a power source needed to operate a carbon microphone since the carbon microphone doesn’t produce an electrical signal on its own.
The quality of a carbon microphone is poor, but despite the poor quality, the carbon microphone had been in use in large quantities as the microphone in a telephone. In the early years of radio broadcasting, the only microphone that was available was the carbon microphone.
A crystal microphone uses the phenomenon of piezoelectricity – the ability of some materials to produce a voltage when subjected to pressure – to generate an electrical signal that is proportional with the audio vibrations in the air.
The quality of a crystal microphone is usually a lot better than a carbon microphone. To obtain the best quality, it is needed to terminate a crystal microphone with a high impedance. This can cause an issue since high impedance microphone cables cannot have a length of tenths of meters due to the capacity of the cable used.
Ribbon microphones are technically a form of dynamic microphone but are generally treated as a separate design because they work and sound very different than their traditional counterparts. The ribbon design includes an extended rectangular diaphragm made of thin aluminum with magnets at either end. When sound waves hit it, it vibrates to create an electrical charge. Most ribbon mics feature a bi-directional (figure 8) polar pattern.
A great ribbon mic offers the most natural sound reproduction. Its frequency range most closely mimics human hearing, so audio doesn’t come in as bright as on condensers or dynamics, but vocals and instruments sound very clear and natural. Ribbon mics are primarily used in recording studios, where you can get perfect positioning and protect them, as they tend to be more delicate than the other types.
Dynamic microphones use electromagnetic induction to convert sound waves to an electric signal. Inside the capsule is a Mylar diaphragm with a conductive coil attached to it. When sound waves vibrate the diaphragm, it moves the coil in a magnetic field, creating an AC voltage. As a result, dynamics are sometimes called moving-coil dynamic microphones.
They’re durable and versatile. Dynamic mics are less likely to overload and distort than condenser mics when capturing high SPL sources such as drums, guitar amps, horns, and vocals. Their capsules tend to be less delicate than condenser mics, making them well-suited to be handheld vocal mics for live performance.
They also have lower sensitivity than condenser mics, requiring higher sound pressure levels (SPL) i.e. louder sources to operate.
Condenser microphones use electrostatic technology. In the most common design, a movable metal diaphragm is attached to a fixed metal plate, and both are charged and have electrodes attached. When sound waves hit the diaphragm, it changes the distance between itself and the plate, creating what’s called capacitance and resulting in small voltage changes that mimic the original wave.
A condenser mic usually requires an external power source to charge it. They typically pull their charge, called “phantom power,” from a mixer or audio interface.
Of the three types of microphone designs, condenser mics generally offer the best high-frequency audio reproduction, which makes them the most common choice for capturing the nuances of voices. Their high-end response also allows them to reproduce better transients, the peaks at the beginning of a sound wave. Hand percussion, such as shaker and tambourine, and acoustic guitar, also benefit from accurate transient reproduction.
Condenser mics come in two basic categories: large diaphragm and small diaphragm. Large diaphragm mics are usually defined as having diaphragms that are 1 inch or larger. Typically, large diaphragm condensers have a more well-rounded frequency response and work best for recording voices. Small diaphragm condensers have the best high-end response and are preferred for recording instruments.
Microphones are very valuable pieces of equipment for many different types of events. Understanding how they work and the best option for specific uses would be helpful for anyone renting, buying, or using microphones. Please contact us for assistance with microphones or any other type of audio-visual equipment, event production or AV installation.
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