How Microphones Work
Different Types of Microphones
There are numerous designs and technologies for microphones but this article is going to focus on the most common types of microphones and the way that they function.
One of the first things contemplated when putting together a home recording studio is which microphones to buy. Trying to decide which microphone to use for different recording applications can be difficult at first, but using the correct microphone can make a huge impact in the outcome of your recording. Knowing how a microphone works and the different types of microphones will give you a better idea of which ones you’ll need for your studio. This article is going to explain the most common ways that microphones transduce acoustic energy (sound) into electric energy and the differences between the main types of microphones.
To start out there’s 3 common types of microphones which include dynamic, condenser, and ribbon. On top of that you have the different polar patterns or “microphone pick up patterns” like cardioid, omnidirectional, bidirectional, etc. And if that isn’t enough there’s always the hundreds of different brands to choose from. To make it easier we’re going to explain the basic concepts of microphones, starting with what a microphone is and how they work, and then explain the difference between condenser, ribbon, and dynamic microphones.
What is a Microphone?
A microphone converts energy from one form to another, which makes it a transducer. An easy way of understanding microphones is thinking of them as speakers working in reverse. Instead of taking electric energy and changing it into acoustic energy (sound) like a speaker, microphones take acoustic energy and turns it into electric energy. The way the energy is picked up and converted is one of the main differences between microphones, but it all starts with a vibrating diaphragm.
What is a Microphone Diaphragm?
A microphone diaphragm is a thin piece of material that vibrates when sound waves hit it, which then causes other parts inside the microphone to pick up these vibrations. These other “parts” then go to work to convert the acoustic energy (sound waves) into electrical energy which is what we refer to as an audio signal. Diaphragms are not all the same and vary between different microphone designs. The size of the diaphragm, the material the diaphragms made of, it’s surrounding structure and the way it interacts with other parts inside of a microphone all play a role in the way the microphone operates.
The way dynamic and ribbon microphones transduce energy is through the electromagnetic induction principle, while condenser microphones use an electrostatic capsule. As intense as it sounds, I’m going to attempt to explain it in relatively simple terms.
Electromagnetic Transduction Principle: In regards to microphones, electromagnetic transduction is simply a coil moving back and forth near a magnet. In dynamic microphones the diaphragm is connected to the coil, and causes the coil to move when the diaphragm vibrates. The coil then starts to generate an electric current as it’s moving near the magnet, which travels out through wires as an audio signal. In ribbon microphones the diaphragm actually is the “coil”, but the same principles apply.
Electrostatic Transduction: Regarding microphones, electrostatic transduction is caused by the distance between two plates changing. These 2 plates have a voltage between them. The back plate stays stationary, while the other (which happens to be the diaphragm in this design) moves when struck by sound waves. When the diaphragm moves towards the back plate the voltage is charged. When the diaphragm moves away from the back plate the voltage is discharged. This configuration creates what’s called a capacitator. Since the capacitator needs a voltage to function, condenser microphones require either 48v phantom power or an internal battery.
What is a Dynamic Microphone?
Dynamic mics are generally more resilient to higher changes in pressure (louder noise), and are ideal for situations where a more sensitive microphone might be overwhelmed and clip/distort. On top of being able to handle louder sounds, they typically can handle more physical abuse and are often used for live performances for both of these reasons. As mentioned above, dynamic microphones use electromagnetic transduction to convert sound energy, and use a stiffer and relatively thicker diaphragm wrapped in a wire coil. Common applications for dynamic microphones are sounds with loud transients like kick drums and snare drums, as well as miking guitar amp cabinets. One of the downfalls of dynamic mics is the limited high frequency response, although in certain instruments and recording applications that could be just what you’re looking for.
Examples of Dynamic Microphones:
- ElectroVoice RE-20 Cardioid Dynamic Microphone: This mic is a legend in the radio / broadcasting industry, and can also often be found in front of bass/kick drums. The RE-20 is one of my favorite dynamic mics. For more info on it here is a review I wrote on the ElectroVoice Re-20 Microphone.
- Shure SM58 Dynamic Microphone: The SM58 is known for it’s superb durability, and is very popular for live performances. For more on the Shure SM58 Microphone here is a review I wrote on it.
What is a Condenser Microphone?
Boasting a wide frequency response range, condenser microphones utilize the electrostatic transduction method as opposed to the electromagnetic transduction that takes place in ribbon and dynamic mics. Some condenser microphones have internal batteries to provide the current required for electrostatic capsules to operate, although it’s more common that they require an external power source known as 48v phantom power. Phantom power can be provided in many preamps and audio interfaces as well as numerous other devices. The sensitivity of condenser microphones makes them more ideal for capturing all the nuances in vocals, but also makes them susceptible to clipping from powerful bursts of sound.
What is a Ribbon Microphone?
Instead of having a thick diaphragm wrapped in a coil like dynamic microphones, ribbon microphones have a thin metallic diaphragm suspended between magnets. Ribbon microphone diaphragms react to velocity of air particles instead of pressure changes from sound waves, which is why they’re sometimes referred to as “velocity microphones”. The most common pick up pattern of ribbon microphones is bi-directional (figure 8), which means they pick up sound from the front and back but not the sides, although they sometimes use hyper-cardioid patterns as well. Ribbon microphones offer a very warm sound, with a rich low end. Because of the thin “ribbon” diaphragm, ribbon microphones can be damaged or destroyed by too much noise and you should avoid using them for very loud applications.
Summary of How Microphones Work
There are many different types of microphones and they all play different roles in recording and performing. With a combined knowledge of how microphones work and which types of microphones work better for specific applications you should be well on your way to deciding what type of microphone collection you need to build for your home studio. If you have any additional questions or would like to give some feedback on the article, leave a comment at the bottom of the page.
Other Information on Microphones: