What Is A Dynamic Microphone? (Detailed Definition + Examples)

Of all the differentiating factors between microphones, they are most often distinguished as one of two major types: dynamic and condenser. Because the term dynamic applies to so many microphones, there’s a lot to know about dynamic microphones.

What is a dynamic microphone? A dynamic microphone is a transducer audio device that converts sound (mechanical wave energy) into audio (electrical energy) via a moving electrically conductive diaphragm, a permanent magnetic structure, and the principle of electromagnetic induction.

In this article, we’ll expand on that definition and discuss the inner workings of dynamic microphones in greater detail. We’ll also touch on some dynamic microphone examples and common applications to better understand this mic type.

Related article: What Are Dynamic Headphones And How Do They Work?

Table Of Contents

• What Is A Dynamic Microphone?
• The Two Basic Dynamic Mic Designs
• What Is Electromagnetic Induction?
• Dynamic Mic Type 1: Moving Coil
• General Characteristics Of A Dynamic Microphone
• Dynamic Microphone Applications
• Dynamic Microphone Examples
• Dynamic Mic Type 2: Ribbon
• General Characteristics Of A Ribbon Microphone
• Ribbon Microphone Applications
• Ribbon Microphone Examples
• Passive And Active Dynamic Microphones
• Differences Between Dynamic And Condenser Microphones
• Related Questions

What Is A Dynamic Microphone?

As mentioned above, the main defining characteristic of a dynamic microphone is that it works on the principle of electromagnetic induction. Therefore, a dynamic mic must have the following:

• A magnetic structure that provides a magnetic field.
• A conductive element in which an electric potential difference (voltage) can be taken via lead wires.
• A mechanism that allows relative movement between the conductive element and the magnetic field.

That pretty much sums up the most basic (though technical) definition of a dynamic microphone! Of course, there is much more to it than that.

The Two Basic Dynamic Mic Designs

Two microphone transducer designs utilize electromagnetism to convert sound into audio. They are known as:

• Moving-coil dynamic microphone
• Ribbon dynamic microphone

We'll get into each of these microphone types in detail shortly, but for now, we'll touch on the basic transducer design.

The Moving-Coil Dynamic Transducer Design

When we hear the phrase “dynamic microphone,” we always bet on it being a moving-coil dynamic microphone. Though ribbon mics are also dynamic, they are referred to as “ribbon microphones” the vast majority of the time.

The moving-coil dynamic transducer is designed with a non-conductive diaphragm with a conductive metal coil (typically copper) attached to its rear side.

The magnetic structure has a cylindrical cutaway that the coil sits within. This structure provides the permanent magnetic field necessary for the electromagnetic induction to take place.

As the diaphragm moves, so too does the conductive coil. The oscillation of the conductive coil within the permanent magnetic field causes an AC voltage to be produced across the coil via electromagnetic induction. This AC voltage is taken via lead wires as the mic's audio signal.

The Ribbon Dynamic Transducer Design

The ribbon dynamic transducer is designed with a conductive ribbon-like diaphragm (typically of ultra-thin corrugated aluminum) and a magnetic structure surrounding the diaphragm's perimeter.

As the conductive diaphragm moves back and forth about resting position within the permanent magnetic field, an AC voltage (mic signal) is produced across it.

What Is Electromagnetic Induction?

So far, we've discussed the basic designs of dynamic microphone transducers. As we know, electromagnetic induction is a key factor in dynamic mics. Therefore, to better understand these mics, we must understand electromagnetic induction.

What is electromagnetic induction? Electromagnetic induction is the production of a voltage across an electrical conductor in a changing magnetic field.

This process was first discovered by Michael Faraday in 1831 and has since been utilized in many electrical components, including inductors and transformers, and electrical devices such as electric motors, generators and, of course, dynamic microphones!

Electromagnetic induction can occur with a fixed conductor and a varying magnetic field, a stationary magnetic field and a moving conductor, or any situation where the relative movement between a magnetic field and a conductor changes.

In the case of dynamic microphones, the magnetic field is stable while the conductor (diaphragm or diaphragm attachment) is in motion.

Because the microphone diaphragms oscillate back and forth about resting position (mimicking sound waves), the magnetically induced voltage across the conductor will be rising and falling. This makes an alternating current and an “AC voltage” across the conductor, which is effectively an electrical representation of the sound.

With that, let's get into each of the two types of dynamic microphones.

Dynamic Mic Type 1: Moving-Coil

Most commonly referred to simply as a “dynamic microphone.”

What is a dynamic microphone? A dynamic microphone is a passive mic that utilizes a conductive coil attached to its diaphragm and a permanent magnetic field to produce its mic signal. As sound causes the diaphragm and coil to move within the magnetic field, a mic signal is induced across it via electromagnetic induction.

Let's have a look at a simplified diagram of a moving-coil dynamic microphone element:

Note that the conductive coil and diaphragm are attached in reality. I have left a space in between them in the diagram to emphasize that they are separate components.

So the magnetic structure is designed to have a circular cutaway where the coil can effectively oscillate. The magnet has one magnetic pole to the interior of the coil and the other pole to the exterior. This creates the proper magnetic field.

As the diaphragm and coil move, a voltage is induced across the coil, which is taken by the electrical leads.

The rest of the circuitry of a dynamic microphone is pretty simple. The electrical leads typically make a circuit with an output transformer or directly with the mic output connection.

A step-up transformer (which is the type at the output, if a transformer is used at all) will help to boost the voltage (amplitude) of the mic signal while also protecting the mic from incoming DC voltage (particularly phantom power). Luckily the robust moving-coil elements will not typically be harmed by DC voltage.

If the dynamic mic is transformerless, the electrical leads connect directly to the mic output, and the signal produces by the element is outputted.

It's important to note that dynamic mics come in a variety of shapes, sizes, address-types, polar patterns, mic brands, frequency responses, price ranges and are designed for various applications.

To learn more about moving-coil dynamic mics, in particular, check out my article Moving-Coil Dynamic Microphones: The In-Depth Guide.

General Characteristics Of A Dynamic Microphone

Though it's unfair to paint an entire microphone type as having distinct specifications, certain aspects of dynamic microphones are regularly true. These include:

• Ruggedness/durability
• Poor high-end frequency response
• Low sensitivity ratings & high max SPL ratings
• Relatively low price point

Ruggedness/Durability

Moving-coil mics are relatively tough. Their transducer elements are physically robust, and their simple passive circuitry is resistant to damage.

Poor High-End Frequency Response

High-frequency sounds have a difficult time moving dynamic diaphragms, so these mics typically suffer in the high-end and have a dark-coloured frequency response.

For more information, check out my Complete Guide To Microphone Frequency Response (With Mic Examples).

Low Sensitivity Ratings & High Max SPL Ratings

The passive transducer element and circuitry of dynamic mics do not output an overly strong mic signal (as condensers do). On the other hand, moving-coil dynamic mics are practically impossible to overload with too loud of a sound.

For more information, check out my articles:
• What Is Microphone Sensitivity? An In-Depth Description
• What Does A Microphone’s Maximum Sound Pressure Level Actually Mean?

Relatively Low Price Point

The simple construction of dynamic microphones makes them inexpensive to build, and so they are often the cheapest microphone option.

Dynamic Microphone Applications

Although dynamic microphones are used to record (or reinforce) plenty of distinct sound sources, there are a few common applications for dynamic microphones:

• Vocals (live performance)
• Vocals (studio recording)
• Drums (close-miking)
• Instrument amplifiers
• Brass

Vocals (Live Performance)

Cardioid dynamic microphones (like the Shure SM58 and Sennheiser e835) are industry-standard vocal mics for live performance. The ruggedness helps with durability in rougher stage performances. The low sensitivity, frequency response and polar pattern allow for high gain-before-feedback. A presence boost, popular to dynamic mics, aids in making the vocals clean in a live audio mix.

Vocals (Studio Recording)

Dynamic mics like the Shure SM7B are go-to mics for recording loud scream-type vocals for harder genres of music. A good dynamic mic can also colour vocals quite nicely to fit more lively recordings.

Drums (Close-Miking)

Individual drums are very loud, and dynamic mics are often chosen for their ability to handle these loud sources without issue. Dynamic mics are used to mic up kicks, snares and toms in many genres and recording styles.

Instrument Amplifiers

Dynamic mics are often chosen to capture the sounds of an instrument amplifier (guitar, bass guitar, etc.). These amps often only output up to 5-6 kHz, so the high-end roll-off common to dynamic mics is not a big deal.

Brass

The big sound of brass instruments is often best heard through dynamic microphones. This is more so the case on live performance stages than studio recordings for the same reasons as the vocal applications.

Dynamic Microphone Examples

• Shure SM57
• Shure SM58
• Electro-Voice RE20
• Sennheiser MD-441 U

Shure SM57

The Shure SM57, nicknamed the “studio workhorse,” is a top-address cardioid dynamic microphone. It has an output transformer, though a common modification includes removing this transformer for an increased bottom end at the expense of output sensitivity.

The Shure SM57 is a go-to on snare drums, tom drums, guitar cabinets, horns, and many other instruments and sound sources on the live stage and in the studio.

Shure SM58

The Shure SM58 is an industry-standard live vocal microphone. This top-address cardioid dynamic microphone has an excellent presence boost to bring a vocal out of a dense/loud mix without the need for tons of processing and EQ.

The Shure SM58 and SM57 are both incredibly durable, making them great choices on the road. The 58 also performs well on the sources mentioned for the 57.

Electro-Voice RE20

The Electro-Voice RE20 is another top-address cardioid dynamic microphone. However, this mic features a larger diaphragm and Electro-Voice's patented Variable-Distance (Variable-D) technology that virtually eliminates the proximity effect.

The EV RE20 excels as a voiceover microphone, finding homes in broadcast/podcast studios and professional vocal booths around the world. This mic is also a top candidate for placement in front of instrument amplifiers, kick drums, horns, and many other sources.

Sennheiser MD-441 U

The Sennheiser MD-441 U is a more expensive dynamic microphone that is marketed as sounding similar to a condenser. Surprisingly, this mic is top-address (through the grille design may fool us) and has a supercardioid polar pattern.

The Sennheiser MD-441 U is an all-star, sounding excellent on all sorts of sound sources.

Dynamic Mic Type 2: Ribbon

Most commonly referred to as a “ribbon microphone” though also a dynamic microphone.

What is a ribbon microphone? A ribbon microphone is a type of dynamic microphone that utilizes a conductive ribbon-like diaphragm suspended within a magnetic structure. As the ribbon moves with sound waves, an AC voltage (mic signal) is induced across it via electromagnetic induction.

To better understand ribbon microphones, I've added a simplified diaphragm of a ribbon transducer element:

In the ribbon element's magnetic structure, we have one magnetic pole to the left and the other to the right of the ribbon to create a sufficient magnetic field. The thin corrugated ribbon does not work nearly as well as a coil when it comes to inducing a voltage via electromagnetic induction, so we need all the optimization possible.

For this reason, some ribbon microphones include active components to boost the signal. We'll get to this in a minute.

So as the ribbon diaphragm moves in reaction to the sound waves, an AC voltage is induced across it. Electrical leads are taken from each end of the ribbon to create a circuit with another component.

Now in passive ribbon mics, this ribbon signal circuit is completed with an output step-up transformer. This transformer boosts the voltage (amplitude) of the signal before it is outputted while also protecting the ribbon diaphragm from phantom power.

With active ribbon microphones, the element's output signal is sent through an active circuit the effectively amplifies the signal while optimizing the impedance of the signal before it is outputted.

Active ribbon mics require power and are more expensive than their passive counterparts. However, they output stronger, more consistent signals that are better optimized for other audio devices (notably microphone preamplifiers).

More on active ribbon microphones in the Passive And Active Dynamic Microphones section.

It's important to note that ribbon mics come in a variety of shapes, sizes, address types, polar patterns, mic brands, frequency responses, price ranges and are designed for various applications.

For more information on ribbon microphones, check out my article Dynamic Ribbon Microphones: The In-Depth Guide.

General Characteristics Of A Ribbon Microphone

Once again, generalizing is tough due to the exceptions. However, there are a few common specifications across ribbon microphones that we should be aware of. They include:

• Fragility
• Bidirectional (figure-8) polar pattern
• Accurate transient response
• Natural-sounding frequency response
• Low sensitivity

Fragility

Ribbon microphone diaphragms are notoriously delicate. Plosives, gusts of air, hitting/dropping, and incorrectly applied powering have the potential to snap the ribbon, rendering the mic useless (until a re-ribbon is performed).

Bidirectional (Figure-8) Polar Pattern

Ribbon elements are designed as close to a true pressure-gradient system as possible. Both sides of the typical ribbon mic diaphragm are equally exposed to sound pressure, which results in a bidirectional (figure-8) polar pattern.

It's also worth noting here that ribbon microphones with bidirectional polar patterns are all side-address.

To learn more about the bidirectional polar pattern, check out my articles What Is A Bidirectional/Figure-8 Microphone? (With Mic Examples).

Accurate Transient Response

The thinness and openness of the ribbon diaphragm allow it to react very precisely to the variations in sound pressure it is subjected to.

For everything you need to know about microphone transient response, read my article What Is Microphone Transient Response & Why Is It Important?

Natural-Sounding Frequency Response

The ribbon diaphragm movement is very accurate, but the transducer process often has a slight decrease in sensitivity as the frequencies of sound increase. This yields a natural-sound high-end response that works particularly well with bright sound sources and digital recording.

To discover all you need to know about frequency response, head over to my article Complete Guide To Microphone Frequency Response (With Mic Examples).

Low Sensitivity

The electromagnetic induction process in a thin conductive ribbon only produces a small amount of voltage. With no internal amplification, the passive ribbon mic will output a low-level signal. Note that active ribbon mics do have internal amplification and higher sensitivity ratings.

Ribbon Microphone Applications

Ribbon microphones are used to record a plethora of different sources and often sound incredible on the source they're positioned to pick up. Let's look at a few familiar applications for ribbon microphones to understand this mic type better:

• Vocals
• Brass
• Guitar amplifiers
• Drum overheads

Vocals

Ribbon microphones, in general, sound astonishingly natural. This allows them to excel on vocals. However, their bidirectional pattern and fragility keep them away from live performances. We must be careful not to damage the ribbon when singing (and therefore sending plosives) into the mic in the studio. It's always best to tilt ribbon mics slightly off-axis, distance the vocalist from the mic, and use a pop filter.

Brass

Brass instruments really come to life in the studio when performed into a ribbon mic. The accuracy and natural/slightly dark character of the ribbon microphones accentuate brass instruments remarkably well.

Guitar Amplifiers

Guitar amplifiers are arguable best miked with ribbon microphones. The typical ribbon mic captures the true sound of an amplifier with ease while also capturing the airiness of the room without overly brightening the sound.

Drum Overheads

Though condensers are often used as drum overheads, ribbon mics also excel in this position. The neutral sound of a pair of ribbon mics can adequately capture a kit's entire sound.

Ribbon Microphone Examples

• Royer R-121
• AEA R84
• Coles 4038
• Rode NTR

Royer R-121

The Royer R-121 is a flagship ribbon microphone from, arguably, the most popular ribbon mic manufacturer: Royer Labs.

This side-address ribbon mic has a bidirectional polar pattern and a low sensitivity rating of -47 dBv Re. 1v/pa.

The Royer R-121 sounds amazing on guitar amplifiers, as a drum overhead or room mic, and even on kick drums if the drummer/genre is light enough.

The R-121 has an active version known as the Royer R-122 and even has a tube version known as the Royer R-122V.

AEA R84

The AEA R84 is based largely on the legendary RCA 44 vintage ribbon microphone.

This microphone is also side-address with a bidirectional polar pattern and a sensitivity rating of 2.5 mV/Pa.

AEA's R84 sounds fantastic on vocals, horns and guitar amplifiers. It also works amazingly well as a room mic and in many other applications.

The R84 has an active version known as the AEA R84A.

Coles 4038

The Coles 4038 is, itself, a vintage classic ribbon microphone even though it's still in production today.

This mic, nicknamed the “waffle iron,” is side-addressed with a bidirectional polar pattern and a low sensitivity rating of 0.6 mV/Pa.

Rode NTR

The Rode NTR is the top ribbon mic from the Australian manufacturer Rode.

This ribbon mic, like the rest of the examples, is a bidirectional side-address mic. However, unlike the rest, it's an active microphone that runs on phantom power. Even for an active mic, its sensitivity rating is quite high at 30.00mV @ 94 dB SPL.

This microphone does a top-notch job capturing the sounds of vocals, brass instruments, guitar amplifiers, and many other sound sources.

Passive And Active Dynamic Microphones

We've covered that electromagnetic induction is a passive process (it does not require electrical power) in which dynamic microphones convert sound into audio. Therefore, the essential transducer component of a dynamic mic is passive.

An additional, somewhat confusing point is that some dynamic microphones are active (they do require electrical power). So what's the deal?

Allow me to precede the answer by stating that moving-coil dynamic microphones are always passive. There's really been no need throughout the history of microphones to add an internal amplifier to a dynamic mic, and the market does not require an active dynamic mic.

Although the output sensitivity of a moving-coil dynamic mic is low, a good microphone preamplifier will be more than effective at bringing the audio signal up to line level for use in professional equipment.

So then it's the ribbon microphones that have active models on the market. Why would a ribbon microphone benefit from active internal circuitry?

The primary reason is that ribbon microphones naturally have very low output sensitivities. A conductive ribbon is much less effective at inducing a voltage via electromagnetic induction than a coil.

Active ribbon mics have internal preamps that work primarily to bring the microphone's output level up to a healthier level.

In optimizing an internal preamp to match the ribbon element, mic manufacturers cover other bases as well.

First, the output impedance of the microphone becomes more consistent. The output impedance of a microphone is frequency-dependent. Depending on the mic preamp (which has its own input impedance), the actual frequency response of a passive ribbon mic could be altered (often for the worse). An active preamp in a ribbon mic helps level the impedance out and optimizes the mic for all preamps.

Additional benefits include lower noise since the gain stage is optimized and the fact that these active mics will require phantom power (so phantom power won't damage the ribbon mic – this is a common concern).

To learn more about active and passive microphones, check out my article Do Microphones Need Power To Function Properly?

Differences Between Dynamic And Condenser Microphones

In the opening of this article, I stated that microphones are often separated into two major groups: dynamic and condenser. The primary difference between dynamic and condenser microphones is the transducer principle.

Dynamic microphones, as we've been discussing, convert sound into audio via electromagnetic induction. Condenser microphones, conversely, convert sound into audio via electrostatic principles.

This major distinction comes with other general differences. A major contrast is that condenser transducers are active (they require power) while dynamic transducers are passive (though some ribbon mics are active due to their internal amplifying circuitry).

Dynamic microphones are generally more durable and are sold at lower prices. Condenser microphones typically benefit from better sensitivity and accuracy (in transient and frequency response).

All the major general differences between dynamic and condenser microphones are listed below:

To learn more about the distinctions between dynamic and condenser mics, check out my detailed article on the Differences Between Dynamic & Condenser Microphones,

Related Questions

Do dynamic microphones require power? Electromagnetic induction is a passive process, and so the basic design of a dynamic microphone transducer does not require any power to function. However, there are active ribbon microphones on the market that require power for their internal preamplifiers.

Are condenser mics good for vocals? Condenser microphones (particularly large-diaphragm condensers) are the standard for recording vocals in the studio, and so yes, they are great on vocals. However, dynamic vocal mics are often preferred over condensers in live situations due to their ruggedness and high gain-before-feedback.

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