What is a headphone driver, and what are the different types?

Woman laying down listening to music with QuietComfort Ultra Headphones

A headphone driver drives air particles, creating pressure waves, which cause ears to perceive sound. There are many different types of headphone drivers, with various strengths and weaknesses. Read on to learn more about headphone drivers and why they matter.

What is a headphone driver?

Drivers are used in all headphones and earbuds, even noise cancelling headphones, and produce the sound that you hear when listening to music. The basic principle of operation is similar across all types of drivers. Magnets create a magnetic field, and electrical signals pass through a conductor, which reacts electromagnetically with the magnet. This creates movement that vibrates a diaphragm, creating sound waves. The various types of drivers are constructed differently but usually feature magnets, conductors, and diaphragms.

Different types of drivers

Dynamic drivers

Dynamic drivers, also known as moving coil drivers, are by far the most common type in over-the-head headphones, using a magnet and voice coil to create sound waves. The basic form of this kind of driver hasn’t changed much in the last century, but technological advances have made great improvements in their efficiency, power, and accuracy.

When an electrical current is passed through a copper voice coil, the attraction and repulsion of this electromagnetic interaction with the magnet causes the voice coil to move. The voice coil is in physical contact with a diaphragm, or cone, making it move, producing the sound waves you hear when listening to a song.

Dynamic drivers are a relatively inexpensive type of headphone driver. Sound quality can vary due to design compromises, or the materials used in their construction, but they are good at reproducing bass frequencies and offer sound quality that is more than enough for most listeners. At high volumes there can be unwanted distortion from the movement of the voice coil causing secondary vibrations to other components, but this can be eliminated by good engineering.

 

Balanced armature drivers

Balanced armature drivers are mostly used for in-ear monitors, due to their smaller size compared to other drivers. They work by having a balanced armature resting on a pivot between two magnets, with a coil wrapped around the armature. When a current passes through the coil, the electromagnetic interaction moves the armature, in turn moving the attached diaphragm.

Planar magnetic drivers

Planar magnetic drivers also use the concept of an electrical conductor moving between fixed magnets as an audio signal passes through it. Instead of a coil attached to a cone-shaped diaphragm, the planar electrical conductor is flat and either attached to or embedded within a film-like diaphragm placed between two flat magnets. Planar magnetic drivers use large magnets, so headphones with this type of driver are heavier and larger than those with dynamic drivers. Planar magnetic drivers produce very accurate sound but also require a headphone amp for best sound quality.

Electrostatic drivers

Electrostatic drivers use a thin film with a static charge applied, suspended between a pair of perforated metal plates. The whole film membrane moves back and forth when an electrical current is applied to the perforated plates. By using thin film instead of voice coils, electrostatic drivers are free from any type of distortion caused by secondary vibrations. The downside is they’re much more expensive than other drivers, and they also need a special amp to boost the audio signal and reduce the current.

Bone conduction drivers

Bone conduction drivers are a relatively new technology, and because they don’t use your ear canal to transmit sound waves, they don’t need to be worn in or over your ears. Instead, they vibrate the jawbones and temporal bones to transfer sound to the inner ear. They can be great for outdoor use, as you can still hear your surroundings clearly, but they also have poor sound isolation and sound leakage. The sound quality is also not as good as other more widely used drivers. That’s why Bose offers open-ear headphones which don’t use bone conduction technology, providing premium sound quality and no audio leakage!

Woman wearing Bose Ultra Open Earbuds

Piezoelectric drivers

Piezoelectric drivers work by applying electrical voltage to either crystal or ceramic material, resulting in vibration through the material that moves a diaphragm. These kinds of drivers are very sensitive, but they require high power to work and produce lower-quality sound. They can sometimes be combined with other driver types in hybrid drivers.

The best of both worlds

Headphones with hybrid drivers or a number of drivers can cover a much wider frequency range, making them capable of better sound quality. For example, sometimes headphones may have one driver covering low frequencies and a separate driver for mid and high frequencies, with a crossover circuit to blend the frequency ranges together and provide a more pleasing, accurate sound.

Driver sound issues

If you’re wondering, ”Why do my headphones keep cutting out?” it’s far more likely to be an issue with the wireless signal of your Bluetooth® headphones than with the drivers. If the driver is the culprit, the sound will either become badly distorted or cut out completely. This could be due to damage to the diaphragm, for example if you drop your headphones. Intermittent dropouts can be caused by interference to the Bluetooth signal and are usually easily fixed with a few simple steps. Driver damage will require repair or replacement.

The choice is yours

Man standing outside and adjusting volume on QuietComfort Headphones

Ultimately, the type of driver used in Bluetooth headphones or wireless earbuds isn’t the only factor in sound quality. The research and development a company dedicates to maximizing the sound quality of any kind of driver is the largest variable, as is the quality of construction. And Bose delivers on those fronts.

Try out different types of headphones and drivers, and see what sounds best to you.

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