Here’s Why Your Wireless Earbuds Sound the Way They Do

You probably don’t give much thought to what’s inside your wireless earbuds when you pop them in every day (I certainly don’t), but it’s kind of amazing how much tech is packed into them. But, regardless of the model, they all have one thing in common: They all have drivers. There are several driver types, though, and how they move and what materials they’re made from varies. Each different driver type has strengths and weaknesses that can dramatically affect the overall performance of the earbud. So which type of driver is best, or at least, best for you?  

What’s a driver?

Drivers, also called transducers, are the tiny speakers inside wireless earbuds that move in response to electrical signals from an audio source. These rapid movements cause compressions and rarefactions in the air, which your ears and brain interpret as sound.

Creating drivers for wireless earbuds presents difficult technical challenges like miniaturization, power efficiency, manufacturing complexity and price. The four main types of earbud drivers currently on the market are: dynamic, balanced armature, planar magnetic and micro-electromechanical systems, or MEMS. Companies are finding some pretty nifty solutions to making each of them sound their best.

Before we get into which drivers are best, let’s talk about each one’s superpower — and Kryptonite.

Dynamic drivers

Though there are important differences, not least size, dynamic drivers are like miniature versions of the drivers in full-size speakers. Dynamic drivers consist of a diaphragm, a coiled copper wire called a voice coil and a magnet. When an audio signal hits the coil, it moves the diaphragm, compressing air as a sound wave. A suspension system pulls the diaphragm back into place, ready to move again.

Dynamic drivers are by far the most common earbud driver type. They can produce a smooth, balanced sound with solid detail and hard-hitting bass. The downside is that high frequencies might not “sparkle” as much as with some other driver types. They’re prone to distortion, which can make music sound muddy at higher volumes. 

Though there are lots of variables, dynamic drivers’ ability to recreate the entire audio range usually makes them the best option for active noise canceling.

As an example, Sony’s WF-1000XM6 true wireless earbuds use diaphragms made of a mix of materials with soft, notched edges and an extremely rigid center. According to Shimo Hiroaki, a senior product manager at Sony, this helps “control high‑frequency resonance at the edge of the driver” and “supports stable driver behavior across the operating range.” Translation: They tame unwanted frequency “bumps” for lower distortion, more controlled bass, clearer highs and more effective ANC.

A variation of dynamic drivers is bone conduction drivers, though these could be considered their own category. Instead of interacting with the air to create sound you can hear, bone conduction drivers do as their name suggests: send the sound through the bones in your head. That might seem weird, but it leaves your ears open to hear normally, so you’re not closed off from the world around you. Shokz is the most famous brand to sell bone conduction headphones and headsets, but other companies have either full bone conduction designs or hybrid designs that use bone conduction drivers alongside other driver types in each earbud.

Balanced armature drivers

Invented in the 1950s by Hugh Knowles for use in hearing aids, balanced armatures have a rigid diaphragm attached via a drive pin to a tiny metal reed (armature) and a voice coil. The armature is suspended between two magnets, and when an electrical signal hits the coil, the magnets move the reed, vibrating the diaphragm and creating sound. 

Balanced armature drivers often offer awesome high-frequency extension and overall clarity, making them great for many acoustic genres, but their tiny size makes their bass response a bit weak compared to dynamic drivers. Many earbuds with balanced armature drivers also have dynamic drivers for better bass, but more on designs like that in a moment.

Planar magnetic drivers

Planar magnetic drivers have a flat diaphragm (plane) with embedded conductive material. When an electrical signal hits the embedded conductor, a magnet on one side moves the diaphragm quickly and evenly, so ideally, distortion is kept at a minimum while creating audio with excellent clarity. They can often work better than balanced armatures, especially for bass, but can also be heavier and with a bigger drain on the already meager earbud battery. While a capable technology sound-wise, other factors mean that they’re not typically found in many mainstream earbuds.  

MEMS

Micro-electromechanical system drivers represent the latest in miniaturization, and they’re an entirely different design from conventional drivers. The diaphragm itself is an extremely thin piezoelectric material and doesn’t require anything other than an electrical signal to deform and create sound. MEMS work best for high frequencies, and less so for bass, but recent advances have resulted in MEMS drivers that can handle the full frequency range. 

The secret sauce: Tuning

To make earbuds that sound great, manufacturers make adjustments to the drivers, the shape of the earbuds and adjust digital signal processing algorithms with the goal of making the earbuds sound good. But what’s “good” to the average listener? Many companies have invested a lot of time and money in trying to figure that out.

Harman, parent company of such storied brands as AKG, JBL and others, used listening tests with hundreds of trained and untrained listeners to determine a target curve that would be liked by most people. Tuning headphones to sound similar to that target increases the likelihood that most people will like the sound. Some companies have used that target to tune their own headphones, while others have come up with their own target curve to more closely match what they think their customers will like.

Balanced armature driver-maker Knowles Corporation, for instance, developed the Knowles Preferred Listening Response Curve. Based on a study of 200 Billboard hit songs and a set of listeners with varying levels of normal age-related hearing loss (including none), Knowles determined that most people prefer a high-frequency boost starting at around 10kHz, where sizzling sounds like vocal sibilants and cymbals happen, often described as the “air” in the music — and where hearing loss most often begins. The company uses that target curve in its tuning guidance for the many big-name manufacturers that use its drivers. 

The future is now: Hybrid-driver earbuds

Each driver type has its merits and champions, but some new wireless earbuds are sporting hybrid-driver designs, hoping for the best of all driver worlds. Hybrids combine the high-frequency expertise of BA, PM or MEMS with the low-end kick supplied by a dynamic driver. Earbuds like the Status Pro X, Baseus Inspire XC1 and EarFun Air Pro 4 plus combine balanced armatures with dynamic drivers. Creative’s Aurvana Ace 3 combines a MEMS tweeter with a dynamic driver. Motorola’s Moto Buds 2 use planar magnetic and dynamic drivers to accomplish a similar goal. The Noble Audio FoKus Rex5 takes it up a notch, with each earbud housing one dynamic, one planar magnetic and three balanced armature drivers! 

While mainstream earbuds will likely still use a single dynamic driver in each earbud for battery life and cost reasons, you can expect to see more hybrid designs in higher-end and audiophile earbuds in the future.