Although headphones have been around since 1910, the world has seen a significant growth in demand for headphones since the founding and launch of Beats Audio in 2006. Beats single-handedly made headphones an iconic form and object of desire for the youth of today. With bold colours and sense of opulence, along with an artist roster that spans across all genres and crosses over into other industries like sport, owning a pair of Beats became a true lifestyle that grew exponentially globally.
This global influence became so strong that it saw Apple purchase Beats Audio in 2014 for a staggering $3 billion. The headphone and earphone market is currently worth circa $10 billion and is expected to grow to over $15 billion by 2025. Whilst it’s clear to note there is a lot of controversy (amongst audiophiles) surrounding beats and their ability to deliver a product that sounds as good as competing brands at similar price points, one thing is for sure, they have paved the way for the rebirth of an entire industry.
While the world has been busy buying into the lifestyle of cool headphones like Beats, existing companies with a long history of making headphones have been pushing the very limits and boundaries of what is possible with headphone design and driver technology. This growing demand for better sound quality from headphones has also laid the foundations and allowed for smaller niche companies to enter the market. These companies have often focused on introducing and pioneering new driver technologies or taking existing technologies from speaker designs and adapting them to work within a headphone design.
This demand has also driven and funded the research and development of new materials, science and manufacturing techniques which has resulted in an explosion of new headphone technologies and designs creating an industry that is as fast paced and competitive like many other consumer electronics markets.
Whilst you browse our extensive range of headphones, you may be faced with a plethora of terms referencing different headphone driver technologies, many people new to the world of head-fi as well as high-end portable audio and headphones may not understand what these are or how they work. We’ve put together this guide in order to give an overview of current mainstream and niche headphone technologies along with new and emerging ones coming to market most recently. Please note this guide focuses specifically on the speaker technologies within headphones and not headphone types for examples open-back headphones and closed-back headphones.
Before we get started you may already be thinking – what is a driver? A driver is the term used to describe the part of a headphone which translates the electrical signals from your media player or amplifier into sound – in essence the speaker!
Dynamic Drivers
Dynamic drivers (sometimes referred to as moving coil drivers) are the most popular type of headphone driver in existence today. The majority of consumer headphone brands that you should already be familiar with like, Sony, Bose, Sennheiser, Beats etc all use this type of technology in their products.
In its simplest form a dynamic headphone driver is derived from a standard piston type cone driver found in loudspeakers which date back as early as the 1920s. They are so universally popular in mainstream headphone design due to two main factors – affordable price and relative ease of construction by comparison to the other available technologies discussed in this guide.
A dynamic driver is typically made up of 4 main components, a magnet (1), voice coil (2), suspension system (3) and diaphragm (4). The structure of this can be seen in the diagram below:
* image copyrighted to https://www.wikiwand.com:
Being adopted from a traditional speaker driver it works in a similar way, an electric current is passed from the source (music player/amplifier) to the coil, this interacts with the magnetic field from the magnet creating an electromagnetic force that moves the diaphragm in a forward like piston motion. It is this movement/vibration which moves air creating sound waves, ultimately music. The general rule of thumb with dynamic drivers is that the larger the magnet and diaphragm, the larger the air displacement is, which means the transducer is capable of a louder sound output.
The more air that can be moved also results in a larger amount of bass frequency reproduction, this is why dynamic drivers are well known for big and bold bass and also commonly used within hybrid earphones/headphones to deliver the low end. Some other benefits include light weight construction so they’re perfect for consumer headphones, good efficiency so they can be driven from mobile phones and portable music players fairly easily.
As with all technologies, there are some disadvantages inherent by design, and with dynamic drivers due to their construction they can be prone to distortion at high volumes, especially when pushed to their limits. This clipping is due to the diaphragm surpassing the excursion boundaries of the driver or when it starts to move off axis in an unstable manor. Secondly, as dynamic drivers have moving parts, these parts need to be bonded together, typically this is done using some type of glue. These bonds can degrade over time making the long-term reliability of dynamic drivers an issue.
As dynamic drivers are used in both headphones and earphones, their size can vary substantially. Dynamic drivers found in in-ears usually range in size from 5mm - 15 mm and 20mm – 50mm for those found in headphones.
There are different types of dynamic drivers on the market like Tesla drivers manufactured by Beyerdynamic, Bio-cellulose drivers from the likes of Sony and Fostex and Ring Radiator drivers produced by Sennheiser. Although they’re all slightly different in structure, and use of materials etc, the core fundamentals and components remain the same as depicted above.
Planar Magnetic
Many believe that planar magnetic drivers are a relatively new technology from the last decade, when in fact they were first conceptualised in 1969 by Jim Winey in Minnesota USA. Initially invented as a speaker driver technology for his start-up company Magnepan, it has gone on to transform and dominate the high-end headphone industry today. The technology first transitioned to headphones in 1970 by Yamaha and branded as Orthodynamic. Back then, the driver technology was introduced as a way of getting more clarity out of headphones, something their dynamic counterparts lacked. For the next 40 years the technology remained virtually unchanged and not many brands focused on developing/improving it or implementing it into their high-end headphone designs.
The fundamentals behind planar magnetic technology resemble a cross between a dynamic driver and an electrostatic driver. It still uses magnets that interact with current running through a conductor but instead of using a fixed cone to push air it uses the vibrations of a very thin membrane that has electrical conductors printed on it, known as the trace. An exploded diagram showing the internals of a planar driver can be seen below:
* image copyrighted to https://www.audeze.com
The magnetic array found in modern day planar magnetic headphones can vary in size, shape, strength, configuration and can also be one sided as well as two sided. These magnets are always placed in front or behind the thin film diaphragm, and when the current is passed through the traces on the film it interacts with the magnets. This then causes the film to move in a push/pull motion. The magnets span the circumference of the diaphragm to make sure the entire diaphragm moves in a uniform planar waveform. The configuration of these magnets along with the complexity of the trace have an impact on the driver movement and its linearity, this in turn yields different levels of harmonic distortion present in the reproduction of sound.
With most planar designs the end goal is to produce a driver which has the thinnest and lightest diaphragm available combined with the strongest magnetic array possible. This results in a driver that can move at lightning fast speeds. This speed can be so fast that in some cases can’t be seen under normal viewing conditions, however, if looked at through a camera that can record at several thousands of frames per second, the driver can be seen vibrating in a similar fashion to a trampoline.
So, what does this all mean for sound quality? Fortunately, the above technology brings a wide range of benefits and improvements to sound reproduction, some of these are listed below:
Low distortion
As planars move across their entire surface area they don’t suffer from distortion like when a dynamic driver meets the limits of its excursion. Even when pushed to extreme SPL levels a planar can replay music with virtually no distortion.
Fast transient response
Due to the lightweight and thin nature of planar drivers (some are 0.5 microns thick, which is 1/10th the thickness of a red blood cell!) combined with the very strong electromagnetic force that drives them, the diaphragm can move at very fast speeds which results in an excellent transient response time. This means the driver can recover very quickly from producing one sound in order for it to reproduce the next. They also tend to sound very coherent and lifelike with great dynamics.
Excellent soundstage
Unlike a traditional dynamic driver which emits a spherical waveform from its relatively small driver, planars move in a linear fashion across their entire surface, resulting in an excellent soundstage and fantastic imaging.
Powerful tight bass response
Good bass reproduction requires effortlessly moving large volumes of air. Most planar drivers have very large surface areas (100mm+, that’s over 50% larger than normal cone drivers) This surface area determines the volume of air that can be displaced while driver flexibility allows for the effective reproduction of low frequencies. Some driver material from leading planar manufacturers like Audeze are so light that they actually weigh less than the air that’s being displaced/moved.
The main challenges surrounding planar technology comes in 2 main forms, weight and fragileness. Although the driver is almost weightless, the magnets which drive them are big and heavy. Therefore, planar drivers tend to be some of the heaviest headphone types on the market. Advances and innovations in magnets have allowed for one sided arrays resulting in some companies being able to halve this weight. Due to the thinness of the driver material it can be very fragile and unstable, therefore it’s important when handling planar headphones extra care is taken, especially when placing them on desks and headphone stands to eliminate any heavy impacts.
Since 2009 Audeze and Hifiman have become the two market leading brands pushing the limits of planar technology, with both companies investing heavily in R&D generating patents across all areas of the technology from magnets to waveguides.
Electrostatic
Similar to planar technology, electrostatic technology was first created for use in speaker design. The original patent for the technology dates as far back as 1953, and was filed by Arthur Janszen of Minneapolis, USA. It wasn’t until the early 70’s when brands like Wilson Audio started using a high frequency electrostatic tweeter in their high-end speaker designs, making them more prevalent.
The technology was first introduced to headphones by a Japanese company called Stax in 1959 with the SR-1 – this went into full production 1 year later. Stax, to this day remains the largest and most dominant manufacturer of high-end electrostatic headphones with a full range at varying price points. Other manufacturers including Koss, Sennheiser, Hifiman and Warwick Acoustics have one electrostatic headphone within their range.
As the name would suggest, electrostatic drivers make use of a static charge to generate sound. Instead of using magnets to push and pull a diaphragm (as is the case with planar and dynamic technologies) an electrostatic charge is placed on the film, the driver remains static whilst a charge is applied. The vibrations required to create sound waves occur to the film as the diaphragm pushes and pulls against positive and negative conductive perforated plates that sandwich it. The absence of moving metal components allows these drivers to produce a virtually distortion-free sound, with very high accuracy and unrivalled high-frequency response.
The diagram below gives you a more detailed understanding of the internal workings of an electrostatic driver:
* image copyrighted to https://www.yourdictionary.com
As their construction is very similar to that of a planar driver, they share many of the same benefits mentioned in the previous section. An additional benefit is that as there is no need for magnets in this design, they tend to be quite a bit lighter and therefore more comfortable. Many believe electrostatic headphones reproduce the sound of orchestral music extremely accurately, with hardly any distortion or coloration of the sound and are therefore the best solution for classical music listening.
There are 2-3 downsides of electrostatic headphones:
Cost
Due to the driver architecture and complex construction process, electrostatic headphones take a long time to build and subsequently demand a premium cost to purchase.
High Voltage Amplifier
Electrostatic headphones can’t be plugged in to a regular source or amplifier, they require a dedicated high voltage amplifier (sometimes referred to as energisers). These are usually big, heavy and expensive. This generally limits the use of electrostatic to home listening and also drives up the cost for a complete system/solution. Most brands that manufacture electrostatic headphones also make a range of energizers specifically for use with their headphones and many only sell them with the accompanying headphones as a complete system.
Bass
Whilst the bass of electrostatic headphones are very clean and fast, they are known to struggle when trying to extend low and reproduce sub bass tones. Some new designs have improved upon this, but they still lack the impact achievable by planar and dynamic drivers.
Ribbon & AMT
The final driver technologies we’ll be discussing are ribbon drivers and Air Motion Transformer (AMT) drivers. We have chosen to group these together as they share many of the same design features, with the main difference being how the diaphragm is composed, whether it’s straight or pleated (ribbon) or folded as is the case with AMTs.
One of the earliest panel style speakers, ribbon speakers were invented in 1930. They consist of a metal-film ribbon (usually aluminium) that is suspended in a magnetic field. An electrical signal is applied to the ribbon which then interacts with the magnets in order to move and create sound. Due to the lightweight nature of the ribbon, they have a very low resistance level and often require a step-down transformer in order to increase the current through the ribbon. Like with planar drivers they can be very fragile and require tremendously strong magnets to perform efficiently and to a high standard.
As ribbons are light in weight and supported in a very strong magnetic field, they are very well controlled, and can respond instantly to the signal input. This gives them excellent transient response and ability to reproduce high-frequencies very accurately.
Raal (a company that has been making ribbon tweeters for loud speakers since 1995) have recently developed a full range ribbon headphone. The headphone, namely the SR1a, is an open baffle, floating near ear design. The drawback to this design is that they require a separate ribbon amplifier and a further 100W min speaker amplifier to power them.
Air motion transformer technology was introduced in the 1960s by German-American physicist Oskar Heil. The design consisted of a folded elastic diaphragm, where single folds open and close in an alternating manner this results in the air driven through the folds is accelerated to a ratio four times as fast as the diaphragm itself. This makes the design of AMT speakers unique to any others currently available that move air as a 1:1 ratio. How this works is depicted in the diagram below:
*Image copyrighted to https://www.hedd.audio
AMT technology was improved and commercialised over a 40-year period by Klaus Heinz. Last year after several years of R&D his company HEDD audio released the world’s first full range AMT headphones. Aptly named the HEDDphone, they have a newly patented VVT technology in order to reproduce the complete audible frequency band (which has never been achieved with an AMT before). This is done by manipulating the geometry and structure of the normally fixed length and width folds so they’re variable. This gives a full linear frequency range of (10Hz–40kHz). This release marks the start of a whole new category of headphone technology and should hopefully extend the frontiers of headphone design and challenge market leaders to produce better headphones at more affordable price points.
Summary
After reviewing all of the above mainstream and niche headphone technologies, it should be clear to see that each one in their respective right has its own positives and negatives. Many of these will correlate to a sound characteristic which one can only pass judgement on if heard in person.
Whether you’re looking for a headphone light enough to use when commuting to work, or the ultimate hi-fi headphone for critical listening at home, there is a headphone and technology on the market for you. Some high-end headphones and headphone systems can cost thousands of dollars, so we advise you take some time to demo before making a considered purchase.
