The Physics of How Earphones Work
Whether it’s listening to music while working out at the gym or immersing yourself in your favourite TV series during a long commute, earphones have forever changed how we listen to music and consume content.
However, very few people would be able to describe how these trusted companions work beneath the surface. So, to help you better understand how the internal mechanism of earphones work and how they convert electrical signals into sound, we’ve put together this simple guide.
The first thing that should be established is: what exactly is sound?
To give a simple answer: Sounds are vibrations, caused by moving objects. These vibrations are taken in by our ears and interpreted by our brain. This means that in order to create sound, mechanical movement is needed.
This is where driver units inside earbuds come into play. Driver units, also called transducers, transform analog signals into vibrations; think of them as miniature-sized speakers. The typical size and corresponding performance of a driver unit differ from earphone to earphone but is typically between 6mm to 15mm. The S500W true wireless earbuds for example have an 8mm driver unit for high quality sound.
In order to create sound, a diaphragm is an integral part of every driver unit and consists of a thin membrane, which creates audio waves when being set in motion. The intensity and direction of the movement is directed by the electrical signal, which enters the driver.
Not all driver units are created equal and they transform electrical current into sound in different ways by moving the diaphragm. So, what are the most common types of earphone drivers and how do they work?
Types of Driver Units
Dynamic Drivers
The term “dynamic driver” is often referred to as “moving coil driver”. The driver unit consists of 3 main components: a magnet, a voice coil, and a diaphragm.
The electrical current flows to the voice coil, which creates an electromagnetic field. The alternating direction of the current causes the voice coil to be either attracted or repelled by the magnets surrounding it, which makes it move back and forth. This movement causes the diaphragm to vibrate and to produce soundwaves. According to the strength and direction of the electronic current, the electromagnetic field is being altered, which moves the coil at an alternating pace and direction. This causes the diaphragm to vibrate and to produce the sound. Sound performance is not only related to the size of the drivers, but also to the materials and overall architecture. Dynamic drivers are more susceptible to audio distortion than other driver types, if the volume becomes too high.
Electrostatic Drivers
As the name suggests, electrostatic drivers utilize static electricity in order to create an electric field. The diaphragm is positioned between two perforated metal plates or electrodes. The current flowing into the electrodes causes them to produce an electric field, which makes the diaphragm move between the plates. The soundwaves find their way to the ear through the perforations inside the electrodes. Electrostatic drivers can produce a wide range of frequencies with very low distortion but need additional amplification.
Planar Magnetic Drivers
Planar magnetic drivers are also called “orthodynamic drivers” and can be seen as a mixture between dynamic drivers and electrostatic drivers. They function on a very similar principle as dynamic drivers do, since they also make use of magnetic fields to generate soundwaves. However, instead of using a coil for movement and a diaphragm to produce sounds through vibration, planar magnetic drivers make use of a diaphragm, which is located between two magnets and which contains thin wires. The diaphragm starts vibrating as soon as electricity moves through its thin wires. Planer magnetic drivers are less susceptible to sound distortion and can produce a clear bass, however they need a further amplifier and usually come at a higher price.
Balanced Armature Drivers
Balanced armature drivers are only available for in-ear monitors (IEM). The name comes from a coil, which is wrapped around an armature and located between two magnets. Armature drivers are called “balanced”, as the distance between armature and the two magnets is equal. The armature is connected to the center of the diaphragm. Once current flows through the coil, the armature becomes magnetic and starts moving, which in turn causes the diaphragm to vibrate. Balanced armature drivers offer a very detailed sound experience, but at the expense of a weaker bass.
There you have it, a simple guide on how earphones work internally and how they produce sound. Have a look at our guide around how true wireless earphones work work if you want to find out more.
