Overview

This section will cover the basics of what 'drivers' are, what types are readily available, and their respective benefits and drawbacks. Keep in mind throughout this guide that this is only to give all the basic information regarding the drivers and what they can do. At the end of the day, the driver selection will be based on what matters most to you in an IEM: bass, clarity, physical footprint, etc.

Thus, reading each driver's operation, benefits, and drawbacks to create your own opinion is crucial.

What are drivers? What do they do?

'Drivers', also called Transducers in general is any technology that converts any set energy from one form to another. A common example of this is everyday phone screens, which take in DC current and convert that into light --commonly done with LEDs or retina displays.

In IEMs this is often done in a similar fashion but from electricity (DC) to moving waves (sound) that can be picked up by our ears (which are also transducers in themselfs).

Types of Drivers

Currently, in the IEMs sphere, the most common types of drivers are:

1. Dynamic Drivers (DD)

2. Balenced Armature (BA)

3. Electrostatic Drivers (EST)

4. Plannar Drivers (PD)

5. Piazoeletric Drivers (PED)

Each one of these drivers have their own benefits and drawbacks when used to creat IEMs, but certain drivers areoften better for specific applications than others.

Dynamic Drivers (DD)

Dynamic Drivers also called 'DD' drivers for short. Are for our all intent and purposes tiny speakers that contain 3 primary things, a voice coil, a permenant magnaet, and a diaphram.

When electric current that carries the audio signal is sent to the driver it energizes the voice coil that sits inside of the round magnaet and causes the newly created magnetic field of the voice coil to interact with the already present magnetic field of the permenant magnet.

this interaction generates a physical force on the voice coil, causing it to move forwards and backwards, this voice coil is usuualy also attached to some kind of membrane or 'cover' that is usually the black rubbery materialyou see from the outside of the speaker that you can see moving.

Though what I just explained is the most common design of drivers, (Electrodynamic Speaker Driver) there are other methods which are often used too, such as Plannar, and Pizeo-eletric which we will talk about later.

Application

Dynamic drivers have been around for a long time and thus are one of the cheapest (in most cases) and most consistent audio transducers in the market. They are often used as single, double, or in mixed hybrid iems to often produce a large, and 'thumpy' bass sound -- though they can produce most of the human hearing range too.

As previously stated, DD drivers often excel at having excellent cost-to-effective ratios as they produce a great bass response which allows music to often have more weight and impact when listened to.

Balenced Armature Drivers (BA)

Balanced Armature Drivers are very similar to DD drivers as talked about previously, but with the major difference coming at the point where the voice coil would be in a traditional DD driver. Unlike a Dynamic Driver, a BA driver contains a centrally 'balanced' rod also called an 'armature' hence in the name balanced armature, this rod is balanced exactly on the ring of the round magnet, and it is placed exactly in the middle of the magnetic field, as to create a net force of zero on the armature, thus perfectly balancing it.

When electricity is sent to the metal coil wrapped around the armature, it causes the magnet's electromagnetic field to interact with the one created by the coil, which pushes or pulls the armature in reference based on the audion current sent to the driver, this armature then intern pushes and pulls a diaphragm, similar to the membrane in aDD driver which moves the air around the entrance of the spout of the driver which created the sound you hear.

Application

Balanced Armature drivers have been utilized often only really in hearing aids and in-ear monitors as their often small size works well with the tight constraints of an IEM shell. Often used in pairs within a crossover network to work together to produce high-quality audio. BA drivers are often used to produce a more detailed and technical sound, what that means in terms of the audial heading range is that most BA drivers are excellent at producing the mids to high frequency with extreme efficiency, often only falling off at the extreme ends of the spectrum. There have been major improvements to the technology that has allowed some to achieve sound production at even the 10-20hz range, and vice versa on the upper end.

To achieve the best setup for BA driver-based IEMs, often most manufacturers utilize a hybrid/multi-driver setup or muti-count BA driver setup to compensate for the inefficiencies within their drivers to create a fuller and more rich sound.

Commonly this is done via a crossover circuit, which is a Analogue Audio filter circuit that splits a inputed signal into multiple sepereate sections that can be modified and processing via differnt devices or in our case, drivers. this allows certain BA drivers to handle the highs, mids, bass seperatly depending on their frequnecy response.

We will go over what crossover circuits are and how to create them in accordance later in this guide. But in general, IEMs are best used when you require a high degree of clarity within a small physical footprint.

Electrostatic Drivers (ESTD)

"Electrostatic drivers, comparitively are more complicated in their operations and thus I will only go over the overarching concept in how they operate."

The configuration of the driver is setup with 2 electrostaticly conductive sheets/grids of metal in a pole/tube shaped shell, in between these conductive grids is placed a ultra-thin membrane film that usually has a high resistivity coating as to spread a constant charge across the entire membraine for low distortion.

When a current is sent into the driver, it causes the grids to generate static electricity which in turn pulls and pushes on the membrane in the middle of the two grids, thus creating physical motion to generate sound.

Application

EST drivers are often used in high-end audio as they have a very small physical footprint compared to DD drivers and have extreme efficiency in producing audio across a large portion of the audible human hearing range, with minimal to almost no harmonic distortion due to their dual grid system which cancels out any over/undertones resonances.

Furthermore, since EST can produce ultra-high frequencies from 15kHz+ they are often built and set up as tweeters reserved for purely the ultra-high frequencies to deliver the most detail. (Not limited to)*

But a common drawback is that often EST drivers lack the gravity when producing sound at the lower end of the spectrum and thus don't produce as impactful of a 'thump' for the bass, and so as mentioned previously, they are often reserved for a certain frequency range within a hybrid driver configuration which allows them to work in the most effective frequency range whilst being supported by other DD, BA, etc. drivers which help create a 'fuller' sound.

Plannar Drivers (PD)

Instead of a cone-shaped diaphragm like in Dynamic Drivers or a tiny rod-like in BAs, planar drivers use a large, flat diaphragm—basically, a super-thin film stretched across a frame. This diaphragm is embedded with a pattern of electrical traces or wires (acting like a voice coil).

On both sides of the diaphragm are arrays of magnets arranged in such a way that the entire diaphragm is evenly surrounded by a uniform magnetic field.

When the audio signal is passed through the diaphragm’s embedded wires, it interacts with the magnetic field and causes the entire flat diaphragm to move back and forth—pushing air across its full surface area to generate sound.

Applications

Plannars are often considsered a almost 'middle-ground' in terms of sound signatures, in how their sound is often considered 'very netural', not nessearliy favoring heavily into the bass like dynamic drivers, or too much intothe highs like electrostatic designs.

Thus, they are primarely used for only producing the mids within an IEMs, though it should be said that they canusually produce the entire audible human hearing range, but often are best suited for the mids as the even distribution of the membrane's movement causes the sound to not tetter to either end of the spectrum.

Additionally, due to their low distortion and fast response, are similar to Piezo-electric drivers in that sense that if an unbiased, and fast transient sound is your goal, it can looked into with a hybrid setup to fully support its fall-off points. Lastly, it's important to consider their sheer size. As the drivers are often much larger than something like balanced armature or electrostatic drivers, they often require a larger physical footprint that may be a bottleneck if that is a major goal for your IEM.

Piezo-Electric Drivers (PED)

Piezoelectric drivers are the most different from the bunch we have discussed till now. They are often considered 'specialists' as long as drivers are considered.

They utilize a physical concept of piezoelectric effect, which in essence is when voltage is applied to a thin metal sheet, it causes it to bend and stretch, thus causing the air around it to move and be pushed as well and thus produce sound.

This method of sound producing is often very precices and ultra fast, and thus PED are considered on the fastestin terms of sound producing and can produce super clear sound in the 1-5kHz ranges (when used for audio gear), and can even go into higher frequnecies if used for other applications.

Applications

These drivers are often used when ultra-fast sound producing is required, in which harmonic distortion is less of a worry and instead, the generation of sound is more prudent.

As such, the drivers often fall drastically below the 1kHz frequnecy range, and are often setup with hybrid driver configuration and thus, heavily require the assitance of other drivers to deliever a fully compasing soundscape. Addionally, since the sound is often made by a metal strip, if not tuned properly the sound can often be overly harsh, and thus requires careful tunning to allow high detailed and tacticality without metalic harshness.

Citations & Image Credits

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2. “Electrodynamic speaker driver,” Wikipedia, https://en.wikipedia.org/wiki/Electrodynamic_speaker_driver (accessed Apr. 21, 2025).
3. “Headphones,” Wikipedia, https://en.wikipedia.org/wiki/Headphones#Balanced_armature (accessed Apr. 21, 2025).
4. “Electrostatic loudspeaker,” Wikipedia, https://en.wikipedia.org/wiki/Electrostatic_loudspeaker (accessed Apr. 21, 2025).
5. “Magnetostatic loudspeaker,” Wikipedia, https://en.wikipedia.org/wiki/Magnetostatic_loudspeaker (accessed Apr. 21, 2025).
6. [1] “Piezoelectric speaker,” Wikipedia, https://en.wikipedia.org/wiki/Piezoelectric_speaker (accessed Apr. 21, 2025).
7. Geoff, “B&O Tech: How to make a loudspeaker driver (a primer),” earfluff and eyecandy, https://www.tonmeister.ca/wordpress/2014/01/31/bo-tech-how-to-make-a-loudspeaker-driver-a-primer/ (accessed Apr. 21, 2025).
8. A. Fox, “The complete guide to balanced armature IEMS/earphones,” My New Microphone, https://mynewmicrophone.com/the-complete-guide-to-balanced-armature-iems-earphones/ (accessed Apr. 21, 2025).
9. A. Wykes, “Headphone driver types: Which one’s just right?,” SoundGuys, https://www.soundguys.com/driver-types-19347/ (accessed Apr. 21, 2025).
10. SoundGearLab-Team, “6 types of headphone drivers explained: Dynamic, planar, etc [guide],” SoundGearLab, https://soundgearlab.com/guide/types-of-headphone-drivers/ (accessed Apr. 21, 2025).