Microphone Types: The 2 Primary Transducer Types + 5 Subtypes
There are plenty of microphones in existence and many different types of microphones. When it comes to the way microphones transduce energy and create their audio signals, there are two primary types of microphones to choose from.
What are the 2 primary microphone transducer types and their subtypes? Perhaps the broadest way to classify microphones is by transducer type. The most common mic types are dynamic and condenser. Dynamic subtypes include moving-coil and ribbon mics. Condenser subtypes include tube, “true” solid-state, and electret mics.
In this article, we'll define what makes a microphone a dynamic or condenser mic. We'll also take a closer look at each of the 5 subtypes of these primary microphone transducers.
What Is A Transducer?
A transducer, simply put, is any device that converts one form of energy into another form of energy.
How are microphones considered transducers? Microphones are transducers because they convert mechanical wave energy (sound waves) into electrical energy (AC voltages). Sound waves vibrate the microphone's diaphragm, and through the mic's method of energy conversion (often dynamic or condenser), a coinciding mic signal is produced.
So microphones are transducers. There are many different types of transducer principles that make various types of microphones.
However, the 2 most common mic transducer types are, once again:
- Dynamic
- Condenser
Each of these transducer types can be further separated into subtypes.
Dynamic microphone transducer subtypes:
- Moving-coil dynamic
- Ribbon dynamic
Condenser microphone transducer subtypes:
- Tube condenser
- True solid-state condenser
- Electret condenser
Let's dive into these microphone transducer types in more detail!
Dynamic Microphone Transducers
What is a dynamic microphone? A dynamic microphone is a transducer that converts sound waves into audio signals via electromagnetic induction. Dynamic mics have conductive diaphragms that move within a magnetic field in order to produce their mic signals. Dynamic mics come in 2 types: moving-coil and ribbon.
If it weren't for electromagnetic induction, dynamic microphones would not exist. Every single dynamic microphone/transducer converts mechanical wave energy (sound waves) into electrical energy (mic audio signals) via electromagnetic induction.
Electromagnetic induction is a physical phenomenon defined as the production of an electromotive force (voltage) across an electrical conductor in a changing magnetic field.
In dynamic microphones, simply speaking, it's the electrical conductor that moves within fixed magnets. However, as the conductor moves through the magnetic field, it experiences it differently (which defines the “changing magnetic field”).
Dynamic microphone signals can be calculated via electromagnetic induction with the following formula:
\mathcal{E} = - \frac{d\Phi_B}{dt}Where Ɛ is the electromotive force or voltage (mic signal)
dΦB is the change in magnetic flux
dt is the change in time
So this means that each and every dynamic microphone needs a conductive metal diaphragm (or a conductive part of their diaphragm). It also means that every dynamic mic requires magnets to provide the magnetic field.
Sound waves cause the conductive diaphragm to move. As the conductive diaphragm moves within the magnetic field, electricity is produced across it. By taking leads off the conductive diaphragm, we effectively harness the converted electrical energy as a mic signal.
Sound waves cause oscillations in sound pressure that go above and below the atmospheric pressure. These high and low pressures cause the microphone diaphragm to move back and forth in two directions. This causes an alternating current to be outputted by the microphone capsule/element. This explains why mic signals are AC.
As mentioned, there are 2 subtypes of dynamic microphones. These 2 types vary in the design of their diaphragms and the magnetic housing around their diaphragms. Once again, the 2 subtypes of dynamic microphones are:
Moving-Coil Dynamic Microphones
Moving-coil dynamics are most often what people refer to when they use the term “dynamic microphone.”
Shure
Shure is featured in My New Microphone's Top 11 Best Microphone Brands You Should Know And Use.
As the name suggests, moving-coil dynamic mics have coils of conductive wire that move within a magnetic field in order to produce their mic signals.
The conductive coils of dynamic mics are attached to their diaphragms. These diaphragms are typically circular and move in reaction to the sound waves around them.
The actual conductive coil can be thought of as a separate piece, though it is attached to the diaphragm. As the diaphragm moves, so too does the conductive coil.
The moving coils are typically made of small diameter copper wire wound many times in a cylindrical shape.
The coil is suspended in a cylindrical space with a magnetic structure to its interior and exterior. This is a peculiar shape for a magnet, and moving-coil dynamics often use separate but attached pole pieces in order to construct the magnetic structure.
Pictured below is a replacement capsule/cartridge for the featured Shure SM58. Notice the smaller circle on the top acoustic foam. This is where the conductive coil attaches to the diaphragm. The diaphragm is just under the acoustic foam and the coil underneath the diaphragm. Unfortunately, we cannot see the conductive coil in this photo.
The magnets and pole pieces that provide the magnetic field are often made of neodymium.
As the conductive coil moves within the magnetic field, electromagnetic induction causes a voltage (mic signal) to be produced across it. A lead is taken from either end of the coil. These leads carry the microphone signal to the mic's output and wherever we need the mic signal to go.
Top 5 moving-coil dynamic microphones:
For more information on moving-coil dynamic mics, check out my article Moving-Coil Dynamic Microphones: The In-Depth Guide.
Ribbon Dynamic Microphones
As discussed, the term “dynamic microphone” typically refers to moving-coil dynamic mics. When talking about ribbon microphones, nearly everyone simply calls the “ribbon mics.”
Royer Labs
Royer Labs is featured in My New Microphone's Top 11 Best Microphone Brands You Should Know And Use.
Though moving-coil and ribbon microphones both convert energy via electromagnetic induction, their capsules/elements are vastly different.
The diaphragm of a ribbon microphone is shaped like, well, a ribbon. This is unlike the circular diaphragms of most moving-coil dynamics and condenser microphones.
Unlike their moving-coil counterparts, ribbon diaphragms are, themselves, the conductors. They are typically constructed out of thin, corrugated aluminum. For example, the featured Royer R-121 (pictured above) has a ribbon only 2.5 microns thick (that's thinner than a strand of a human hair).
Pictured below, we see the ribbon element of the featured Royer R-121 ribbon microphone.
In this image, we have the corrugated aluminum ribbon in the centre. The main magnets are to the sides of the ribbon's length, and other magnets are held within the overall baffle (the ribbon microphone housing).
The ribbon diaphragm is attached at the top and bottom of the baffle. This acts to properly hold the ribbon in place while also taking electrical leads off the 2 ends of the conductive diaphragm.
Magnets are housed to either side of the ribbon and around the baffle. They provide the magnetic field necessary for magnetic induction as the conductive ribbon diaphragm moves in reaction to external sound waves.
Top 5 ribbon dynamic microphones:
For more information on dynamic ribbon mics, check out my article Dynamic Ribbon Microphones: The In-Depth Guide.
Condenser Microphone Transducers
What is a condenser microphone? A condenser mic is a transducer that converts sound waves into audio signals via electrostatic principles. Condenser capsules are fixed-charge capacitors. As the diaphragm moves, the capacitance changes and a mic signal is produced. Condensers come in tube, true solid-state, and electret subtypes.
The condenser microphone capsule is a bit trickier to explain than the ribbon element/baffle and moving-coil capsules. That being said, all 3 of the condenser subtypes are built very similarly.
The term “condenser,” when the condenser microphone was first invented in 1916, meant what “capacitor” means today. In other words, condenser microphones are “capacitor microphones.” They are named so due to their capsules, which act as parallel plate capacitors.
So condenser microphones convert sound waves to mic signals with parallel-capacitor-like capsules. The basic design of a condenser's parallel plate capacitor is as follows:
- Diaphragm (movable plate): this plate moves according the sound waves around it.
- Backplate (stationary plate): this plate does not move, allowing for the variation in distance between the plates that is critical to condenser transducers.
Pictured below is the legendary AKG CK 12 condenser capsule.
The CK 12 had gone through a few revisions before settling on a 6-micron Mylar diaphragm. The tensioning ring was originally brass, attached via screws, but was later changed to nylon with a friction attachment mechanism.
The AKG CK 12 is actually a multi-pattern condenser microphone capsule with 2 diaphragms that share a common backplate. By combining the signal of the 2 diaphragms in different combinations, various polar patterns are achievable (omnidirectional, cardioid, and bidirectional).
Capacitors are designed to hold electrical charge. For any condenser microphone to function properly, its capsule must be sufficiently charged. The method of charging the capsule is the defining factor of the 3 condenser mic subtypes.
Once a condenser capsule is charged, any variation in capacitance will cause an inversely proportional variation in voltage (which ultimately becomes our mic signal). The capacitance is varied as the distance between the two plates changes.
So, if the capsule is charged, then as the diaphragm moves, a mic signal will be outputted!
Below is a picture of a Neumann K67 condenser capsule. Yet another legendary dual-diaphragm (multi-pattern) capsule that has been developed and integrated into plenty of high-quality microphones.
The K67 capsule was designed with polyester-film diaphragms and is centre-terminated. It is perhaps the most copied studio microphone capsule today.
Condenser microphone signals can be calculated via the following electrostatic principle formulas:
V=\frac{Q}{C}Where V is voltage (mic signal)
Q is charge (practically constant)
C is capacitance
C = ε\frac{A}{d}Where C is capacitance
ε is the permittivity of the dielectric material (constant)
A is the area of the circular diaphragm and backplate (constant)
d is the distance between the parallel plates
It's important to note that the outputted voltage (mic signal) from condenser capsules is nearly always high-impedance (in the GΩ range). Active components are required as impedance converters so that the mic signal will survive the journey to the mic output (and beyond) without severe degradation.
Condenser capsules will vary greatly in their design. Still, they all are built on the same general blueprint of a parallel plate capacitor with a charged movable diaphragm and stationary backplate.
Of all the design differences within condenser microphones, it's the method of powering/charging/polarizing the capsule that defines each of our 3 condenser mic subtypes. Once again, they are:
Tube Condenser Microphones
Tube condenser capsules are charged/polarized by an external power source. The impedance of their signals is then converted, and the signals are amplified via built-in microphone vacuum tubes/valves. These tubes also require external power supplies.
AKG
AKG is featured in My New Microphone's Top 11 Best Microphone Brands You Should Know And Use.
Tube condenser microphones were the original condenser mics on the market, and many of them have reached legendary status. Vintage tube mics and “new-vintage” boutique tube microphones are highly sought after for their “tube sound.”
Top 5 tube condenser microphones (all discontinued):
- AKG C 12 (built with the aforementioned CK 12 capsule)
- Neumann U 47
- Telefunken Ela M 251 (built with the aforementioned CK 12 capsule)
- Blue Bottle
- Neumann U 67 (built with the aforementioned K67 capsule)
4 of the 5 microphones mentioned above are explained in detail in my article Top 12 Best Vintage Microphones (And Their Best Clones).
Solid-State “True” Condenser Microphones
Solid-state (also generally called FET) condenser microphone capsules are charged/polarized via an external power source. Usually, these microphones do not have external power supplies and instead rely on phantom power to function.
Neumann
Neumann is featured in My New Microphone's Top 11 Best Microphone Brands You Should Know And Use.
Rather than having tubes to amplify the signal and convert the impedance, solid-state condensers are built with transistors.
The “true” tag on these microphones was not originally part of their name. Rather, it came about when electret solid-state microphones began entering the market. Initially, electret materials were made for lower-quality microphones, and so the term “true condenser” was coined to distinguish between electret condensers and externally polarized solid-state condensers. Since then, electret microphones have improved drastically in quality and performance.
The advent of solid-state condensers was a big step forward in microphone technology. Once understood, solid-state mics were easier and cheaper to make and largely replaced their vacuum tube predecessors.
That being said, there is a huge market for vintage tube mics and “new-vintage” boutique tube mics.
Top 5 “true” solid-state condenser microphones:
- Neumann U 87 (built with the aforementioned K67 capsule)
- Neumann KM 184
- AKG C 414 XLII (built with the aforementioned CK 12 capsule)
- Neumann TLM 103
- Schoeps MK 5 / CMC 6
Electret Condenser Microphones
Electret condenser microphone capsules are permanently charged/polarized by having electret material incorporated into their capacitor-like capsules.
Rode
Rode is featured in My New Microphone's Top 11 Best Microphone Brands You Should Know And Use.
However, electret condensers are still active and do require external power for their impedance-converting transistors to function properly.
This power is supplied in a variety of ways, depending on the electret microphone in question:
- Phantom power (+48 V DC): The featured Rode NT1-A requires phantom power
- DC bias (+5 V DC): The featured Sennheiser ME2 requires DC bias
- USB power (+5 V DC): Many USB mics are electret condensers and get their polarizing voltage via USB connection.
- Note than batteries could supply the power mentioned in this list
As mentioned, electret condenser microphones are permanently charged by the electret material in their capsules. The term “electret” is based on the terms electrostatic and magnet and defines a material with a permanently embedded static electric dipole moment. Modern mics typically utilize PTFE plastic as their electret materials.
In the history of the term “true condenser,” we have discussed the early shortcomings of electret mics. Nowadays, electret mics will hold their charges consistently and over long periods of time. Some very high-quality microphones on the market are electrets!
Sennheiser
Sennheiser is featured in My New Microphone's Top 11 Best Microphone Brands You Should Know And Use.
There are 3 main kinds of electret microphones:
- Foil/diaphragm electret: the diaphragm is made of the electret film. This is the cheapest, most common, but the lowest quality type of electret. Electret film does not make a particularly good mic diaphragm.
- Back electret: the electret film is applied to the stationary backplate of the mic capsule. The diaphragm is then free of any electret material.
- Front electret: the traditional backplate is removed from the capsule design and is replaced simply by the inside surface of the capsule. An electret film is applied to the rear side of the diaphragm.
Electret microphones are the most common transducer subtype in the world. They make up the vast majority of microphones on the market today. To name a few applications:
- Studio microphones
- Lavalier microphones
- Broadcast microphones
- Boundary microphones
- Shotgun microphones
- Cell phone, laptop, and other electronics
- Hearing aids
- Many more
A variety of electret condenser microphones:
- Rode NT1-A (studio microphone)
- Sennheiser MKE 2 (lavalier microphone)
- Shure Beta 57A (handheld broadcast microphone)
- Crown PZM 30D (boundary microphone)
- Sony ECM-674 (shotgun microphone)
A Note On Large Versus Small-Diaphragm Condenser Microphones
Without getting too far off the topic of comparing transducer types, I'd like to mention the difference between small and large-diaphragm condensers. This distinction is common among condenser mics while not so important with dynamic mics.
- Small diaphragm condensers (SDCs) generally have a diaphragm diameter of 0.5″ (12.7 mm) or less.
- Large-diaphragm condensers (LDCs) generally have a diaphragm diameter of 1″ (25.4 mm) or more.
Small diaphragm condensers are often used for close-miking instruments and recording ambience, while large-diaphragm mics are often used on vocals and medium-distance-miking. Of course, there are no rules for this, but this is usually what I see in my work.
SDCs, generally speaking, have numerous benefits over LDCs, including better transient response, extended high-frequency response, and more consistent polar patterns.
LDCs, generally speaking, have lower self-noise ratings than their SDC counterparts.
For more information on SCD and LDC microphones, check out my article Large-Diaphragm Vs. Small-Diaphragm Condenser Microphones.
General Differences Between Dynamic And Condenser Microphones
Let's take it back to the 2 main transducer types and list out some general differences between dynamic and condenser microphones:
| Dynamic Microphones | Condenser Microphones |
| Electromagnetic induction transducer | Electrostatic principle transducer |
| Typically passive (do not require power) *some modern ribbon mics are active* | Always active (require external power) |
| Low sensitivity ratings *except active ribbons* | High sensitivity ratings |
| Poor or rolled-off high-frequency response | Flat or accentuated high-frequency response |
| More colouration in frequency response | Less colouration in frequency response |
| Less expensive | More expensive |
| Very high maximum sound pressure level rating | Lower maximum sound pressure level rating |
| No self-noise *except active ribbons* | Have self-noise |
| Sensitive to electromagnetic interference | Insensitive to electromagnetic interference |
Related Questions
What microphones are best for recording vocals? Large-diaphragm condenser microphones are the go-to choice of most professionals when recording vocals in a soundproof environment. However, in less-than-ideal situations, large-diaphragm dynamics or even lavalier mics are preferred for greater rejection of extraneous noise.
What microphones are best for cameras and video? Shotgun and lavalier microphones are standard for audio recording in video production. Shotgun microphones are commonly attached directly to cameras and boom poles and are very directional. Lavaliers attached to the talent capture the talent's voice while rejecting much of the environment.
Choosing the right microphone(s) for your applications and budget can be a challenging task. For this reason, I've created My New Microphone's Comprehensive Microphone Buyer's Guide. Check it out for help in determining your next microphone purchase.
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