IEMs drivers work using various principles. We are going to break them down in this article. Let’s start with electromagnetic induction.

Electromagnetic Induction

Electromagnetic induction is a fundamental principle that explains the relationship between electrical currents and magnetic fields. When an electric current flows through a conductor, it generates a magnetic field around the conductor.

Conversely, when a conductor experiences a changing magnetic field, it induces a voltage across the conductor.

In the context of audio technology, this principle is utilized in a unique way. A conductive coil is used to transmit an alternating current audio signal. This current passing through the coil generates a changing magnetic field.

The coil is wrapped around a movable armature, which is positioned between two magnets. As the armature is exposed to the varying magnetic field, it interacts with the magnets and begins to vibrate.

To convert these vibrations into sound, the armature is mechanically connected to a diaphragm. The diaphragm moves in synchronization with the audio signal, producing sound waves that correspond to the audio being transmitted.

Let’s start by exploring the fundamentals of headphone drivers before delving into the specifics of balanced armature drivers.

Headphone Fundamentals

Headphone drivers play a crucial role in the design of headphones. They are the transducers responsible for converting electrical audio signals into mechanical sound waves.

Analog audio signals, which power headphone drivers, consist of alternating currents.

When connected to the headphone drivers, the audio source (such as a headphone amp or smartphone) delivers these AC signals, which are then reproduced by the drivers as audible sound waves.

It’s important to note that for digital audio devices, the audio signals must first be converted from digital to analog format to properly drive the drivers. This conversion is accomplished using digital-to-analog converters (DACs). DACs can be found within headphone amplifiers and are often located near the headphone jacks of digital devices.

Balanced Armature Drivers IEMs – A Summary

Balanced armature drivers are a type of driver commonly used in in-ear monitors (IEMs). They are known for their accuracy and detail in sound reproduction. Here are some key points about balanced armature drivers in IEMs:

How They Work

Balanced armature drivers use a tiny armature, or a balanced armature, that is suspended between two magnets. When an electrical current is passed through the coil in the armature, it moves back and forth, driving a diaphragm to produce sound.

Advantages

Balanced armature drivers offer several advantages over other types of drivers. They are known for their precise and accurate sound reproduction, making them ideal for applications where detail and clarity are important, such as in professional audio monitoring or audiophile listening. They also tend to be smaller in size, allowing for more compact IEM designs.

Sound Signature

Balanced armature drivers are often associated with a neutral or balanced sound signature, meaning that they aim to reproduce sound as accurately as possible, without emphasizing any particular frequency range. However, the sound signature can still vary depending on the specific design and tuning of the IEM.

Multiple Drivers

Many IEMs utilize multiple balanced armature drivers to cover different frequency ranges. By combining multiple drivers, manufacturers can achieve a more comprehensive and balanced sound reproduction.

Customization

One advantage of balanced armature IEMs is the ability to customize the sound signature by adjusting the number and configuration of the drivers. Some IEMs even offer switchable filters or adjustable sound nozzles to fine-tune the sound to personal preferences.

Limitations

While balanced armature drivers excel in accuracy and detail, they may not provide the same level of bass impact and extension as dynamic drivers. However, this can be compensated for by using multiple drivers or implementing hybrid designs that combine balanced armature drivers with other driver types.

Overall, balanced armature drivers are popular in IEMs for their accurate sound reproduction and compact size. They are often favored by professionals, audiophiles, and musicians who prioritize clarity and detail in their listening experience.

How Do Balanced Armature Earphone Drivers Work As Transducers?

Balanced armature drivers, also known as BA drivers, are a key component in balanced armature IEMs/earphones. These drivers are small and have size limitations, which is why they are commonly used in earphone-type headphones.

A single BA driver has a limited frequency response, which means it can only reproduce a certain range of frequencies effectively. To overcome this limitation and achieve a wider frequency response, many BA IEMs/earphones use multiple BA drivers.

Each BA driver is responsible for reproducing a specific range of frequencies. For example, one driver may handle the low frequencies, another driver may handle the mid-range frequencies, and yet another driver may handle the high frequencies. This division of frequencies allows each driver to specialize in its assigned range and produce more accurate and detailed sound.

The different BA drivers in a balanced armature IEM/earphone work together to create a balanced and accurate sound reproduction. They are typically housed in a small and compact enclosure, making them suitable for in-ear use.

It's important to understand the functioning of BA drivers to appreciate the capabilities and limitations of balanced armature IEMs/earphones. By dividing the frequency range among multiple drivers, these earphones can achieve a more balanced and detailed sound signature.

Tuning The Balanced Armature Driver

Extensive damping is often required to level out the frequency response in balanced armature drivers. Additionally, many BA transducers do require multiple drivers to effectively produce a wide frequency response.

Manufacturers of balanced armature drivers and units are aware of and tune various factors that affect the sound quality. Some of these factors include:

Size and Internal Volume

The size and internal volume of the BA driver play a significant role in determining the maximum output level. Larger volumes allow for larger diaphragms and greater diaphragm movement, resulting in higher sound pressure levels.

Armature Mass and Stiffness

Increasing the mass of the armature allows for greater magnetic flux and improves low-end frequencies. On the other hand, reducing the mass and increasing the armature stiffness can increase the bandwidth of the system but may worsen the low-end response.

Membrane Stiffness and Diaphragm Mass

The stiffness of the membrane and the mass of the diaphragm also impact the sound produced by the BA driver. Adjusting these factors can help achieve the desired frequency response.

Armature Damping

Damping is crucial in balancing the response of the BA driver. It helps control unwanted resonances and ensures a more accurate and balanced sound reproduction.

Acoustic Filters

Acoustic filters are often used in BA drivers to shape the frequency response. These filters can be designed to attenuate certain frequencies or adjust the overall sound signature.

Sound Outlet

The design of the sound outlet, or nozzle, can affect the sound quality by influencing the dispersion of sound and the interaction with the ear canal.

Tube Length and Diameter

In some BA IEMs, tubes are used to deliver sound from the driver to the ear. The length and diameter of these tubes can impact the sound characteristics, such as the bass response and overall tonal balance.

Tube Damping

Damping materials may be used inside the tubes to control resonances and improve the overall sound quality.

To overcome the limitations of BA drivers in reproducing low frequencies, some balanced armature earphones incorporate additional drivers such as moving-coil dynamic drivers dedicated to producing the low-end. This hybrid driver configuration allows for a more extended frequency response and improved bass performance.

By carefully considering and tuning these factors, manufacturers can optimize the sound quality and performance of balanced armature IEMs/earphones.

Using Multiple Drivers With CrossOvers

The limited frequency responses of balanced armatures make them sound great in specific frequency ranges, but they often perform poorly when tasked with covering the entire audible frequency range.

Their tuned resonances may work to their advantage in hearing aids if a patient has a specific null point in their hearing sensitivity. However, a single BA driver may underperform with in-ear monitors, which are designed to reproduce a full audio mix for a performer.

Therefore, many in-ear monitors utilize multiple balanced armature drivers to produce their wide frequency responses.

Pros Of Balanced Armature Earphones

We've highlighted some important advantages of balanced armature drivers. Here's a breakdown of each point:

High Efficiency/Sensitivity

Balanced armature drivers have a relatively low mass and are easily moved by audio signals. This means they can produce high sound pressure levels even with low-level audio signals. As a result, they don't require much amplification. However, they perform best when driven by ultra-low impedance output sources.

Miniature Size

Balanced armature drivers are small in size, making them well-suited for earphones and in-ear monitors. Their compact design allows for multiple drivers to be used in a single earpiece, enabling a wider frequency response and more accurate sound reproduction. In fact, balanced armature drivers can occupy less than half the volume of the smallest dynamic headphone drivers.

Wide Variety of BA Driver Designs

Balanced armature drivers come in various designs, each with its own tuning characteristics. There are wide-range drivers, low-end woofer-style drivers, mid-range drivers, and high-end tweeter-style drivers. Manufacturers can combine these differently tuned drivers to sculpt the frequency response of their earphones/IEMs, achieving the desired sound signature.

Passive Working Principle

Balanced armature drivers operate on principles of electromagnetism and do not require power to function properly. This makes them passive components and allows for the design of passive crossover systems. These crossovers delegate different bands of the audio signal to different drivers, ensuring a balanced and accurate sound reproduction.

While balanced armature drivers offer numerous advantages, it's important to note that they also have limitations, such as the limited frequency response and the size constraints mentioned earlier. However, manufacturers have been able to overcome these limitations through careful design and the use of multiple drivers in their earphones/IEMs.

Cons Of Balanced Armature Earphones

Strong Resonance Peaks And Poor Frequency Response

One of the challenges associated with balanced armature drivers is the presence of strong resonance peaks in their frequency response. These resonance peaks can cause variations in the accuracy of sound reproduction, leading to a less linear frequency response.

Balanced armature drivers have inherent resonant frequencies due to their mechanical and acoustic properties. These resonances can result in peaks and dips in the frequency response, affecting the overall tonal balance and potentially introducing coloration to the sound.