How Dynamic Mics Work?

Understanding the mechanics of the dynamic mics will help you in making the correct choice with your next microphone.

Dynamic mics work on the principles of electromagnetic induction, producing electric current which is interpreted as a sound signal. However, it is not a holistic explanation because there is much more to these devices, which is critical to understand to make the choice whether you need a dynamic mic or not.

We have dedicated this entire piece to dynamic mics and will explain everything from their anatomy, and mechanism, and the several types that are available on the market. Stay with us to become a dynamic mic geek.

a) The Anatomy and Mechanics of Dynamic Microphones

The anatomy of a dynamic microphone is fairly simple and is centered around a magnet. A metallic coil is attached with a moving diaphragm which is further connected with wires to transmit electrical signals. The entire construction is pretty sturdy, allowing dynamic microphones to withstand high sound pressure levels.

The audio signal is produced on the principles of electromagnetic induction. As the sound waves hit the diaphragm, it starts to move along with the metallic coil. The movement of the metallic coil within the magnetic field creates an electric current, which is then transferred toward the connector via the wires attached to the diaphragm. Afterward, the signal is transmitted to the preamplifier, audio interface, or any other signal-processing device.

While the placement of different components can vary between different types of dynamic microphones, the fundamental principles remain the same.

b) How Does A Dynamic Microphone Differs From Condenser Microphones

The construction of a condenser microphone is drastically different from a dynamic mic because it does not use any magnetic component. Instead, it relies on an electrically charged backplate and a moving diaphragm. As the diaphragm moves by the force of sound waves, it creates a difference in voltage that is then transmitted to processing devices in the form of a sound signal.

Furthermore, the construction of condenser microphones is relatively delicate allowing them to capture subtle differences of the different notes. However, unlike dynamic microphones, these mics cannot work as well under higher sound pressure levels. Thus, these microphones are generally preferred for studio recordings, whereas dynamic mics are typically used for live performances and recording of loud music instruments.

That said, it is important to mention that condenser mics require an external power supply to power the backplate, which is known as phantom power. It is either provided by the audio interface, amplifier, or dedicated power supplies that can be attached with microphones.

c) Types of Dynamic Microphones

Dynamic microphones can be categorized into different types based on two factors: design and polar pattern. Let’s look at them one by one.

1. Based on Design

Dynamic mics can be divided into two categories based on design, including moving-coil dynamic mics and ribbon dynamic mics.

• Moving Coil Dynamic Microphones: The design of these mics, which are also known as coil microphones, is almost similar to a speaker wherein a metallic coil is attached to the diaphragm that moves within a magnetic field created by a strong magnet. 

That said, these mics work in entirely opposite fashion to the speakers. Instead of producing sound via diaphragm membranes, the diaphragm of mics moves within the magnetic field by the pressure of sound waves generating an electric charge, which is interpreted as a sound signal. These are the most widely used dynamic microphones.

• Ribbon Microphones: The fundamental working principle of the ribbon mics is the same as their moving coil counterparts, but instead of using a conductive wire, a thin aluminum ribbon is suspended in the magnetic field to produce electromagnetic induction. These microphones are more sensitive than moving coil mics and are often used in studios to record loud instruments.

2. Based on the Polar Pattern

Polar or pickup patterns describe how a particular microphone picks up sound from different directions. Based on polar patterns, dynamic microphones can be divided into the following categories:

• Cardioid or Unidirectional: Cardioid or unidirectional dynamic microphones pick up sound from one direction only. It allows the cardioid mics to reject the sound from other sound sources, keeping the resultant audio clear of the background noise. This phenomenon is known as off-axis rejection.
• Bidirectional Mics: Bidirectional microphones pick up sound from two opposite directions, which are used to create a stereo effect. These microphones reject the sound from two directions and pick up from the other two. You can use them to record two sound sources that are positioned side by side.

• Omnidirectional Mics: Omnidirectional microphones pick up sound from all directions, allowing them to capture the sound around the main source. Such microphones can be used for recording vocals of the background singers and other applications such as recording ASMR audios.

• Multiple Polar Patterns: Traditionally, the microphone could only have one polar pattern, but modern dynamic microphones come with multiple polar patterns. Users can switch between different polar patterns based on their applications to get the best results. You can also use this omnidirectional pickup pattern to counter the proximity effect.

d) Differentiating Features of Dynamic Microphones

Dynamic microphones offer several features that cannot be made available in other mic types because of the design restraints. These set dynamic mics apart and make them good for specific applications. The features include:

1. Better Pressure Handling

The sturdy construction of dynamic mics allows them to withstand higher sound pressures, thereby giving them higher max SPL. Thus, these microphones can work incredibly for loud musical instruments like kick drums, electric guitars, and violins. While condenser mics can also be used for recording instruments like acoustic guitars, their performance goes downhill with louder instruments.

2. Low Background Noise

Dynamic microphones have lower sensitivities than their condenser counterparts, which means they may not be able to capture the subtle changes between different notes. However, the upside of it is they cannot capture faint background sounds, thus keeping the audio clear of the background noise. It is exactly why the sound of music does not experience distortion even when crowds of thousands are cheering for the musicians.

3. Frequency Response

Generally, dynamic microphones have narrower frequency responses than their condenser counterparts. Much of it has to do with the sensitivities, but it certainly does not mean that the sound quality of dynamic mics is bad by any means. A condenser microphone can have a broader response, but it may not be flat, potentially producing issues in sound reproductions.

Whereas, on the other hand, the frequency response of dynamic mic is narrower, allowing manufacturing to easily control it, consequently enabling better and more natural sound reproduction.

4. Wireless Capabilities

Dynamic microphones do not need phantom power to work, unlike condenser mics. It allows for a wireless design, which is more convenient for seminar halls and churches. Creating a wireless system for other professional microphones is a bit tricky given the mechanics involved in delivering phantom power.

5. Low Self Noise

Self-noise is the noise a microphone produces in the absence of any other sound signal. The sound of the source has to match the level of the sound source to become noise-free, which is quite challenging while recording faint audios. Condenser microphones are notorious for higher noise, whereas dynamic microphones are efficient at keeping it down. 

6. Low Impedance

Microphones transmit signals in the form of AC voltages and impedance is essentially the resistance of AC signal. A smooth transfer of voltage can be ensured only if the output impedance is higher than the input impedance. So, if a microphone has a higher impedance you will have to tweak several settings to get it to an optimal level. Fortunately, dynamic microphones avoid the hassle because they have low impedance in the first place.

7. Durability

Moving coil microphone does not only offer good sound quality but also sturdy construction. The lives of dynamic mics are much longer compared to their condenser counterparts, because of their ability to withstand abuse. Furthermore, the durability also allows users to travel with them without needing special storage cases, making them more portable.

e) Applications of Dynamic Microphones

The differentiating features of the dynamic mics enable several applications that can be only carried out effectively via dynamic microphones. These include the following:

1. Live Sound Reinforcement

Dynamic mics are widely used in concerts for miking vocals and instruments. It’s because they check the right boxes with their features. An ideal microphone for concerts should have high SPL, less sensitivity to feedback, and portability, all of which are unique selling points of dynamic mics.

2. Instrument Miking

You can also use it to make individual components of musical instruments such as snare drums and kick drums, because of their ability to withstand higher SPL. They are also often used to capture the sound of preamp guitars, offering a rugged solution for close-miking loud guitar cabinets.

3. Podcasting and Broadcasting

Dynamic mics are also quite popular in the podcast and broadcast industry because of their affordability, and ability to handle a variety of voice types and ambient conditions.

4. Public Address (PA) Systems

Dynamic microphones are also available with wireless capabilities making them ideal for public speaking. They are often used in churches and seminar halls.

5. Studio Recordings

While condenser microphones are the go-to choice for studios, dynamic microphones, especially the ribbon mic, are often used in studios too. They can be used to record playback music, because of their better noise rejection and to make other loud sound sources.

6. Interviews and Field Recordings 

Dynamic microphones work the best for interviews and field recordings because they can keep the background noise down, producing clearer audio. 

7. Karaoke

Dynamic microphones can handle a loud sound source within close proximity, making them ideal for karaoke setups. 

Frequently Asked Questions