What Are Headphone Drivers?
It’s a well-known fact that not all headphones are created equally. Besides the obvious differences such as how they fit your ears, various features like Bluetooth and noise cancelling and even what their intended uses are, there are other more subtle differences that can make a huge difference in your sound quality. One such difference is driver type. Headphones are essentially a set of tiny speakers that sit in, on or around your ears and like all speakers, they have drivers.
What Are Headphone Drivers?
A driver is the part of the speaker which compresses and refines air to create sound waves. The drivers in a pair of headphones are generally considered the most important part of the headphones because they’re what make the sound you hear; the better the driver, the better the sound. Not all drivers are created equally however; there are several different types of headphone drivers that can have a dramatic impact on the performance and sound quality of a pair of headphones.
The most common driver type used in headphones is the Dynamic driver. Dynamic drivers, also known as the moving coil driver, are designed with a permanent magnet, usually neodymium, a voice coil and a conical diaphragm. A dynamic headphone driver looks pretty much identical to any typical home theater speaker. Dynamic driver headphones are capable of delivering a full range of sound with more than enough detail and clarity for the average listener.
Dynamic driver headphones will function perfectly fine without a headphone amplifier (although they usually will sound better with one) and can be found in everything from budget friendly earbuds to audiophile-grade over-ear headphones.
Balanced Armature Drivers
Balanced armature drivers use basically the same components of a dynamic driver, magnets and voice coils to produce sound waves. How they function, however, is much different. A balanced armature driver uses a coil wrapped around an armature which is held in between two magnets until it is stimulated by an electrical current. When stimulated, this armature is magnetized which causes it to rotate one way or the other around a pivot point which moves the diaphragm to create sound. The strength of a balanced armature driver lies in the midrange, they tend to struggle reproducing frequencies below 20 Hz and higher than 16,000 Hz.
Higher end balanced armature driver headphones often have multiple armature drivers which divide predetermined frequency ranges between them by utilizing a passive crossover network. As a general rule, the more balanced armature drivers a headphone contains, the better they can handle the low and high frequency ranges (but not always). Balanced armature drivers are generally used in in-ear earbuds because of their compact size and low impedances. Another benefit of the compact size of balanced armature drivers is that they are commonly used in hearing aids.
Electrostatic drivers are generally only found in high end headphones (though not exclusively) because they require much higher voltages to operate. Electrostatic drivers are made up of an extremely thin membrane, usually a coated PET (Polyethylene terephthalate) film, stretched between two metal plates (electrodes). An electrical signal is applied to the metal plates to create an electrical field. The result of this electrical field is that, depending on its polarity, the speaker diaphragm is drawn toward one of the plates which forces air through the perforations in the diaphragm which generates the sound wave. Unlike dynamic and balanced armature drivers, electrostatic drivers have no moving metalwork.
Electrostatic drivers are much more sensitive and handle a significantly wider frequency range and produce hardly any distortion. Unfortunately, due to their higher voltage requirements, electrostatic driver headphones require a separate headphone amplifier.
Planar Magnetic Drivers
Planar magnetic drivers, also known as orthodynamic drivers, operate in a similar fashion to electrostatic drivers. A planar magnetic driver is made up of a relatively large membrane suspended between two sets of oppositely aligned magnets. An electric charge is applied to the membrane to induce movement and produce sound waves. As a result of the entire membrane being equally charged and suspended within a uniform magnetic field, any changes in the electrical charge to the membrane causes movement in uniform across the entire membrane surface.
Planar magnetic driver headphones are known for having greatly reduced distortion levels as well as better bass response than other headphones because of the large surface area of the membrane producing the sound waves. In general, planar magnetic drivers are found in high-end, audiophile-grade headphones. Another thing to be aware of, while planar magnetic drivers don’t require as much power as electrostatic drivers, they still generally need to be used with a headphone amplifier.
There are other types of headphone drivers available, but they are used much less commonly and typically only for specially designed headphones. These include technologies like the Heil Air Motion Transformer driver, Ribbon Planar Magnetic driver and Magnetrostriction headphones (sometimes referred to as ‘Bonephones’).
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