What Are The 3 Most Common Types of Microphone Construction?
The Basics – How microphones work
Let’s begin with the most basic question: What is a microphone and how does it work?
To put it simply, a microphone is an electronic device that converts sound pressure into an electrical signal that is amplified by a separate electronic device for monitoring (listening to) or recording the desired sound. The sound pressure waves act on some element within the microphone, usually a thin membrane called a diaphragm. In most cases, the movement of that diaphragm creates the electrical signal.
Sound waves are picked up by the mechanisms in the microphone and, depending on the type, will capture sound from different distances and directions from the microphone. The distance and direction of the microphone is the pickup pattern, and this defines the type of microphone you would use for different projects.
What are the three types of microphone construction?
Most people will only deal with three types of microphone construction: condenser, dynamic, and ribbon. These are the main construction types used in most recording and broadcasting scenarios.
We know what you’re thinking – what are the key differentiators I need to know about? Well, look not further and read on below to find out!
Condenser microphones are also called capacitor microphones. There are two diaphragms inside a condenser microphone’s capsule, with a fixed charge between them. This charge is powered by an external power source. (See our articles “What is Phantom Power?” and “What is Plugin Power?”) The sound waves cause the first diaphragm to move, changing the distance between the two diaphragms and this changes the capacitance between the two diaphragms. The change in capacitance in turn changes the voltage level on the electrical signal output.
Condenser microphones are the preferred microphone for voiceover artists and in many television and movie productions. The main advantage condenser microphones have over dynamic microphones is their faithful rendering of the voice or musical instrument, due to their increased sensitivity to tone and amplitude. This increased sensitivity is due to the low mass of the diaphragm. Due to its low mass, it can react to short, high frequency pressure variations.
As previously mentioned, they require some type of external power. Less expensive microphones usually require “plug-in power.” More expensive microphones typically require “phantom power.”
This increased sensitivity has the drawback that condenser microphones are usually very susceptible to feedback, mic rumble and bumps. This can cause difficulties for live sound environments. They very often need to be mounted inside shock mounts to reduce extraneous sounds. For studio environments they must normally be operated in a quiet environment to avoid capturing even low-level extraneous sounds.
Large diaphragm condenser mics are ideal for vocals while small diaphragm condensers (sometimes called pencil microphones) are great for instruments with a lot of detail within the higher frequency ranges. Large diaphragm condenser mics are typically designed to pick up sound from one or both sides of the microphone while small diaphragm condensers typically pick up sounds primarily from the end.
It is not uncommon for top-level narrators and production studios to spend thousands of dollars on high-end large-diaphragm condenser microphones, like the Neumann U87.
Filmmakers and television producers often use a special type of condenser microphones called shotgun microphones. These microphones, which have a more directional polar pattern than other commonly used microphones, capture more sound in front of the microphone than to the side or behind it. We will discuss shotgun mics in detail later in this article.
Dynamic microphones are also called moving coil microphones. As the sound waves cause the diaphragm to move, a coil of wire attached to the diaphragm also moves. That coil of wire surrounds a stationary magnet, As the coil moves relative to the magnet, a voltage is created which makes up the output signal. (Speakers operate on the same principle, but in reverse, as shown in the animation on this site.
Dynamic Microphones are commonly used when the sound source is quite loud such as a live performance. They are also used when trying to reduce ambient noise and are typically used on music stages, in radio studios, or podcasting and live streaming setups.
The advantage dynamic mics have is that they are strong and durable and do not usually require external power. Due to their lower sensitivity, they generally need to be placed quite close to the sound source. Because of this, dynamic microphones have a significant proximity effect. The proximity effect boosts the lower frequencies when the microphone is close to the instrument or mouth. This makes dynamic mics an ideal vocal microphone. However, they do tend to produce a more artificial tone with the human voice, when compared to condenser or ribbon microphones.
Dynamic mics are also less likely to be overloaded or distorted by high sound levels when compared to condenser microphones due to their lower sensitivity. This lower sensitivity means that they can also be hand-held with less handling noise than a condenser mic.
Due to their coil and magnetic construction, dynamic microphones convert sound to electricity with no additional circuitry. This simplicity eliminates internal noise, meaning you can use more gain without little or no hiss or hum.
Dynamic mics also tend to be less expensive when compared to condenser microphones, for comparable sound quality. For example, the popular dynamic instrument microphone the Shure SM57 is available for less than $100. High-end dynamic microphones such as the Shure SM7B vocal microphone is less than $400.
Dynamic mics, however, offer fewer choices in pickup patterns. They are only available in omnidirectional and cardioid polar patterns. We will discuss the various pickup patterns in a separate article.
Ribbon microphones are also called velocity microphones. Technically, they are a variation of a dynamic microphone.
In a ribbon microphone a very thin, electrically conductive ribbon, usually an aluminum alloy 0.6-to-4 microns thick, is suspended in the field of a permanent magnet. As the sound waves cause the ribbon to move relative to the magnet, a voltage is created which makes up the output signal.
Ribbon microphones are typically used in professional audio studios when looking for a warm and vintage sound. They tend to be expensive and fragile.
The low mass of the ribbon allows its movement to follow extremely small and high frequency changes in sound pressure. A high-quality ribbon mic, such as the Royer R-121, can capture the most faithful representation of sounds of any of the microphone types. This makes them ideal for voices and instruments. However, their delicacy and need to be perfectly positioned makes them less than ideal. They are not well suited for recording environments where they could be knocked about and the ribbon damaged.
Ribbon microphones are inherently bi-directional. Sounds from the front and back of the ribbon are captured at the same level. Sounds from the side, parallel to the ribbon, will place equal pressure on both sides of the ribbon resulting in no signal at all.
The ribbon diaphragm reacts in a nonlinear fashion relative to sound pressure. In other words, the relation between sound pressure and voltage is not consistent. Human perception of loudness is similar. This creates the more natural sound that ribbon mics are known for.
Ribbon microphones are also less susceptible to electronic noise than condenser microphones as they typically use circuitry.
Our final thoughts
Whilst they are all great, the main difference between the three types is in their diaphragm. The diaphragm is the mechanism that reacts to sound pressure level and converts it to an electrical signal. That electrical signal is what ultimately drives an amplifier or recording device.
For more information on selecting the correct microphone, please feel free to contact us!
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