Posted on May 11 2018
If you are looking to purchase a headphone that suits your needs, it is important that you understand how they work and what makes them tick.
There is a lot more to it than just picking the ones that look aesthetically pleasing to the eye. Headphones are made up of many parts, one of which is called the transducer or the driver unit.
So what are headphone drivers? The driver unit is made up of magnets, voice coils and a cone-like diaphragm (measured in mm) and is one of the most essential pieces of the headphone. Its job is to convert the electrical signal into a sound wave that the ear can understand.
However, there is more than one type of driver unit located in a set of headphones. The drivers can range in size from 8mm to 15mm for earbuds and 20mm to 50mm for headphones.
While you may think that the quality of sound is linearly related to the size of the driver unit, it is not necessarily the case. Instead, it is the variation of technologies used to build the drivers which make the difference.
Typically, the size is an indicator of how big the sound can be, although the structure of the unit motor can affect the overall sound.
It is worth noting that it is possible for headphones to have more than one driver to manage the different ranges of frequencies.
Do the number of drivers matters?
While a single driver has the capability to produce sound between 20Hz and 20kHz, it does have its limitations. And that is where multiple drivers enter into the equation. Where more than one driver is involved, filtering is used to segregate the range of frequencies allowing each driver to focus on a particular range.
But, just like the driver size, a headphone with multiple drivers does not automatically makes it a great headphone. A poorly produced quad driver headphone will not rival a well-made single driver headphone.
Types of Driver
Lastly, there are drivers with different types of core mechanism. Each has their own unique ways of producing sound. In this section, we will be exploring five types of headphone drivers that you should know about.
The five types of headphone drivers are:
- Dynamic or moving coil
- Balanced armature
- Planar magnetic
- Magnetostriction or bone conduction
1. Dynamic or Moving Coil Driver
Dynamic, or moving coil, drivers are the most common driver. No surprises here, considering that it is the cheapest transducer on the list.
How does dynamic driver work?
The driver uses the physics of magnetism and electromagnetism to create movement, which leads to sound creation.
There is three mains part that makes up the core of a dynamic driver:
- a neodymium magnet
- voice coil
- a diaphragm that is attached to the voice coil
The magnet magnetizes the voice coil which makes it an electromagnet. Once the voice coil receives current, it creates a magnetic field that head in directions determined by the flow of the current. The voice coil is repelled and attracted towards this magnetic field. Subsequently, this moves the attached diaphragm and it displaces the air around it, creating sound.
The large the air displacement, the higher the volume. To recreate realistic bass response in a driver, the driver must be able to displace air. This is why a dynamic driver is great at creating the bass response.
Since the mechanism is simple, dynamic drivers are very effective and do not require much power to reach high volume.
However, one of the biggest complaints about dynamic drivers is that the audio is susceptible to distortion, especially at high volume. This is also known as “non-linear distortion”. This effect can be attenuate by good engineering though. Hence, it is unfair to plainly associate dynamic driver with poor quality.
- Able to create a good amount of bass response without the need for excessive power
- Dynamic drivers are very cost-effective
- Dynamic drivers that are of poorer quality are susceptible to audio distortion at higher volume
2. Balanced Armature Driver
Balanced armature (BA) drivers are smaller than dynamic drivers and, because of their size, are only available in in-ear monitor (IEM).
They are known to be more expensive than their dynamic driver counterparts.
How does Balanced Armature work?
The driver consists of a miniature arm (armature) inside a coil of wire surrounded by two magnets. The top and bottom magnets determine the movement of the armature. When there is no net force on the armature, meaning it is at equal distance from both magnets, we say that it is “balanced”.
From the diagram, you can see that the armature is attached to the center of the diaphragm.
When current flows through the coil, it magnetizes the armature, causing it to pivot towards either magnet. This pivoting movement will move the diaphragm and produce sound as a result.
Tune to specific frequency
This type of driver can be tuned to cover a specific frequency, although the range tends to be a little limited. You may find that one single set of IEMs can have as many as four different drivers to complete the sound.
Works hand in hand with Dynamic drivers
The difference between BA and dynamic drivers is that BA does not displace air to produce sound. This results in a lack of bass response. This is why you can find IEMs with multiple BA drivers in combination with one dynamic driver. The dynamic driver will make up for the lack of bass response.
A good example of such IEM is the excellent 1More Triple Driver.
There is an upside to the BA mechanism in relative with the Dynamic Driver. Since it does not need to displace air to produce sound, an IEM with BA driver will not have an additional air vent. This provides a better isolation which in turns gives you a more detailed sound.
- Drivers can be tuned for optimal quality in specific frequency
- Better performance in the treble frequency than dynamic driver
- Sounds are more detailed
- Balanced armature drivers are generally more costly than dynamic drivers
- Need additional drivers to get a better bass response
3. Planar Magnetic Driver
Planar magnetic driver, also referred to as orthodynamic driver by Yamaha, is featured more in open-back, over the ear headphones. The drivers are extremely thin and are usually located in high-end headphones.
How does planar magnetic driver work?
The drivers are based on a similar principle to that found on the dynamic driver headphones – using magnetic fields to produce sounds.
So instead of moving the voice coil like the dynamic drivers, the diaphragm (a thin flat film) is directly affected by the magnetic field to produce sound.
And since the whole diaphragm has to be evenly vibrated, larger or more magnets are used and this adds on to the weight of the headphone. It also results in the need for more power from the audio source or purchasing an external amplifier.
Hence, they are not as portable as the dynamic drivers and are generally purchased for home use. Headphones with planar drivers also have a higher price tag than dynamic drivers.
There are companies like Oppo who recognise the need for a planar magnetic headphones that are lightweight and has low impedance. The Oppo PM-1 weighs only 395g and its impedance level is only 32 Ohm.
The sound offered by planar magnetic drivers is of a high standard with relatively no distortion and has good transient response.
The bass response for planar headphones is excellent. This is due to the combination of the large thin diaphragm and strong electromagnetic force leading to the ability to displace a large amount of air.
- Planar magnetic headphones provide excellent quality and low-distortion sound
- Excellent bass response
- Necessary to have a headphone amplifier
- Larger and heavier
4. Electrostatic Driver
Electrostatic drivers take advantage of static electricity – the basis of which lies in the fact that like charges repel while opposites attract. The vibrations occur as the diaphragm pushes and pulls against conductive plates (negatively and positively charged respectively) or electrodes, and the air is pushed through the perforations. This action, along with the continuously changing electrical signal, results in sound waves that are understood by the ear.
As the driver is quite complex and requires special amplifiers known as energizers, they are usually found in the high-end open-back headphones. Electrostatic drivers are relatively uncommon and are more expensive.
However, what they lack in portability and affordability, they definitely make up in the sound arena and the extremely life-like soundstage. The electrostatic driver can produce significantly better sound than any other headphone available and this is reflected in the sale price.
- Electrostatic drivers provide distortion-free sound
- They offer a life-like soundstage
- They are very expensive to buy
- Electrostatic driver-based headphones require an amplifier
- Large and bulky
Have a look at some of the headphones produced by Stax, HiFiMAN or Beyer. They are seemingly the leaders in the electrostatic headphone market.
5. Magnetostriction or Bone Conduction
Headphones and drivers, in particular, have come a long way thanks to modern invention and design. Bone conducting or magnetostriction headphones are an excellent example of this, as the drivers bypass the eardrum sending the vibrations directly to your inner ear via bone conduction.
It sounds a bit like sci-fi, however, but they are particularly helpful in situations where the ears need to be left unobstructed. Joggers who need to hear the sound of oncoming traffic over the source of the music can find these useful. They are especially helpful for individuals who have hearing problems as well. You can even purchase bone conducting headphones which can be used underwater. Also known as “bonephones”, these unique headphones have limited capabilities when compared to other, more conventional, headphones.
- Able to hear external sounds while enjoying your music
- Can aid those with particular hearing loss
- Limitations to their fidelity
While the final choice may come down to cost and availability, it is still worth knowing all the facts before you make your final headphone choice.
For the most part, the dynamic driver is a first-rate purchase for effectiveness and price, but there are circumstances where the other drivers may be more useful for your needs.
A purist audiophile might consider an electrostatic pair is useful if portability is not required and a high price is not necessarily an obstacle. The planar magnetic headphones might fit your appetite if you have a bigger budget and want to try something aside from dynamic driver. Or maybe you need the bone phones with their unique capabilities?
Whatever kind of headphone you are seeking, our recommendation is to do a bit of research before you buy and try them for yourself.
***Credit to headphonesty