If you've even gone on a deep search to find a perfect pair of high-end headphones, you've likely stumbled upon planar magnetic headphones (or at least the term). The planar magnetic headphone type works a bit differently than the typical moving-coil headphones that make up the majority of the market, providing advantages and disadvantages to the listener experience.
What are planar magnetic headphones? Planar magnetic headphones are transducers that convert electrical energy (audio signals) into mechanical wave energy (sound waves) via electromagnetic principles. Their planar drivers are designed with thin electrical conductors embedded on a diaphragm that vibrates between two magnetic arrays.
In this in-depth article, we'll improve upon the simple definition from above and discuss planar magnetic headphones in detail to further our understanding of headphones and audio in general.
What Is A Headphone Driver?
Let's begin with a primer on headphone drivers.
The headphone drivers are the most important pieces in headphone design. They are the transducer elements that effectively replicate the audio signals as sound.
Analog audio signals are electrical signals with alternating currents. The drivers are designed as part of a circuit that passes these AC signals from an audio source (headphone amp, smartphone, etc.) to the headphones.
Note that digital audio must be converted into analog audio to interact with and drive the headphone drivers properly. This is done with DACs (digital-to-analog converters), which are found within headphone amplifiers and in close proximity to the headphone jacks of digital devices.
To learn more about headphone amplifiers and headphone jacks, check out the following My New Microphone articles:
• What Is A Headphone Amplifier & Are Headphone Amps Worth It?
• How Do Headphone Jacks And Plugs Work? (+ Wiring Diagrams)
• Differences Between 2.5mm, 3.5mm & 6.35mm Headphone Jacks
Note, too, that headphones nearly always have two drivers designed to convert two different audio signals. This allows for effective playback of stereo recordings which are commonplace in music and television.
For more information on how headphone drivers receive their intended audio signals, check out the following My New Microphone articles:
• An In-Depth Look Into How Headphone Cables Carry Audio
• How Do Wireless Headphones Work? + Bluetooth & True Wireless
As an audio signal flows through the driver, the driver causes a diaphragm to vibrate and produce a sound wave that mimics the audio.
How does this happen? Well, there are multiple working principles for different headphone driver types.
To read about all the different headphone driver types, check out my article What Is A Headphone Driver? (How All 5 Driver Types Work).
Electrostatic headphones work on electrostatic principles, while bone conduction headphones work with piezoelectricity.
The most common working principle of headphones, bar none, is electromagnetism. Planar magnetic headphones work on this principle, which is best described through electromagnetic induction.
What Is Electromagnetic Induction?
Electromagnetic induction describes electromagnetism quite well.
It states that an electrical current flowing through a conductor will cause a magnetic field to be produced in and around the conductor.
Similarly, it states that a voltage will be produced across an electrical conductor in a changing magnetic field.
With a conductive diaphragm and an applied audio signal, the planar magnetic driver produces a varying magnetic field around the diaphragm. This magnetic field interacts with permanent magnets in the driver structure to cause diaphragm movement and, therefore, sound waves.
How Do Planar Magnetic Headphone Drivers Work As Transducers?
Now that we know the purpose of headphone drivers and the basics of the electromagnetic working principle, we can dive into how planar magnetic headphones work.
It's important to note that the determining factor of planar magnetic headphones is the driver. Planar magnetic headphones can be designed as headphones or earphones; closed-back or open-back; circumaural (over-ear) or supra-aural (over-ear); and any other form factor.
I'll repeat that it is the planar magnetic driver type that makes “planar magnetic” headphones.
For more information on the form factors listed above, check out my article What Are The Differences Between Headphones And Earphones? and The Complete Guide To Open-Back & Closed-Back Headphones.
As an aside, planar magnetic headphones are also referred to as Orthodynamic headphones due to the popularity of Yamaha's Orthodynamic (planar magnetic) headphones of the 1970s.
The Planar Magnetic Headphone Driver
If you're familiar with moving-coil dynamic drivers and electrostatic drivers, it may be helpful to envision the planar magnetic as a sort of hybrid. It works on the dynamic principle of electromagnetic induction but is designed similarly to the electrostatic driver with a diaphragm sandwiched between two arrays.
To explain how the planar magnetic driver works, let's begin with the design components and a simplified cross-sectional illustration:
As we see in the diagram above, there are 3 key components to the planar magnetic driver:
- Conductive traces
The magnets of the planar magnetic driver are designed in arrays to either side of the diaphragm. There must be space between the magnets to allow air and sound to escape from the driver, and the magnetic field lines must be concentrated at the diaphragm for maximum efficiency.
There are plenty of different styles of magnet arrays in planar magnetic drivers. We'll discuss common arrays in the next section, appropriately titled Planar Magnetic Magnet Arrays. For now, we'll discuss a single array to get an idea of how the driver works.
The magnetic array of a planar magnetic headphone driver may resemble the following illustration:
The arrays to the front and back of the diaphragm are designed in such a way that they apply an even field of magnetic flux at the conductor/diaphragm. This is referred to as an isodynamic magnetic field.
As we can see from the diagram above, the magnetic flux density is very high at the diaphragm to achieve maximal diaphragm movement.
As previously mentioned, the arrays are also designed with enough space between the magnets to allow sound to escape from the driver.
Now let's discuss the diaphragm.
The diaphragm is a key component of [nearly] every sound transducer (there are rare exceptions) that moves air and produces sound waves.
Headphones, loudspeakers and microphones all have diaphragms.
Related article: What Is A Microphone Diaphragm? (An In-Depth Guide)
However, headphone diaphragms, by themselves, are useless if they are not designed to move in accordance with an audio signal. Different driver types utilize different designs and working principles to cause diaphragm movement.
A planar magnetic headphone diaphragm is designed with an attached/embedded thin, serpentine conductor.
The diaphragm and conductor form a thin movable membrane, and the magnetic structures follow this plane to the front and rear of the diaphragm. This, combined with the electromagnetic working principle, give the planar magnetic driver its name.
We can see this serpentine design in the following image of the Fostex T50 (link to compare prices on Amazon and B&H Photo/Video):
When the planar magnetic headphones are connected to an audio signal, this flat embedded conductor effectively passes an electrical signal with an alternating current.
If we remember our discussion on electromagnetic induction, we'll know that this alternating current will produce a varying magnetic field that coincides with the audio signal.
As the diaphragm experiences this varying magnetic field, it interacts with the magnetic fields of the two arrays. The attraction and repulsion of the magnetic fields cause the diaphragm to move relative to the audio signal.
The isodynamic field created by the two carefully designed magnetic arrays is critical to ensure that the relationship of the current flow and the force exerted on the diaphragm is constant, regardless of the position of the diaphragm/conductor.
So what happens is as follows:
- The audio signal (alternating current) passes through the conductor.
- This flow of current causes a varying magnetic field within the conductor and diaphragm.
- The varying magnetic field interacts with the permanent magnetic fields of the magnetic arrays.
- The diaphragm moves due to the attraction and repulsions between the magnetic arrays.
The diaphragm movement pushes and pulls air, producing sound waves while doing so. These sound waves are representative of the audio signal. This is how planar magnetic headphone drivers function as transducers.
For more information on sound and audio, please read my article titled What Is The Difference Between Sound And Audio?
Unlike the commonplace moving-coil drivers that produce spherical wavefront sound waves, planar magnetic drivers produce sound waves with a planar wavefront.
This is because the conductive coil in moving-coil dynamic drivers acts as a sort of “point source” in a centre concentric circle of the diaphragm. As the coil moves, it causes a more rounded diaphragm movement. This creates a spherical sound wavefront.
On the other hand, Planar magnetic diaphragms have their conductors placed across almost the entire area of the diaphragm. As the conductor moves, it moves the entire diaphragm (except for the perimeter/circumference connected to the housing). This creates a planar sound wavefront.
Spherical wavefronts tend to “flatten out” toward a more planar wavefront as they travel through a medium.
Headphone drivers, however, are positioned close to our ears. If they produce spherical sound waves (like moving-coil drivers do), then the spherical wavefronts will hit our ears differently than what we normally experience. This has an arguably unnatural effect that some audiophiles note in their experiences with moving-coil and planar magnetic headphones.
This last point is worth mentioning though it is likely not a huge differentiating factor. We certainly hear spherical and planar wavefronts differently, but this is likely not a major factor in the subjective performance of the headphones.
Planar Magnetic Magnet Arrays
There are different designs for the magnetic arrays of planar magnetic headphones. So long at there is an isodynamic field, the magnetic arrays will function optimally, and the headphones will produce sound linearly relative to the audio signal.
Again, this means the arrays to the front and back of the diaphragm are designed in such a way that they apply an even field of magnetic flux at the conductor/diaphragm.
Let's have a look at a few diagrams of potential planar magnetic magnet arrays:
Single-Sided Magnetic Arrays
Some planar magnetic drivers only have a single magnetic array on one side of the diaphragm. To open/improve the path between the driver and the listener's ear, the array is positioned to the outside of the driver.
The need for isodynamic fields is nullified in single-sided drivers. So long as the array supplies sufficient permanent magnetic field strength at the diaphragm, the driver will work.
In theory, single-sided designs have lower sensitivity ratings since the permanent magnetic field concentration at the diaphragm is weaker. Therefore, more electrical current is required to move the diaphragm.
For more information on headphone sensitivity, check out my article The Complete Guide To Headphones Sensitivity Ratings.
However, superior transparency may be achieved in these designs due to the fact that there is no ear-side array to obstruct the propagation of the sound waves.
Single-sided planar magnetic headphones also tend to be lighter in weight due to the lack of ear-side arrays.
That being said, there are plenty of other factors that affect headphone driver quality. Just because a driver is single-sided does not necessarily mean it is less sensitive, nor does it mean the sound quality is more accurate.
Pros & Cons Of Planar Magnetic Headphones
As with everything in life, there are pros and cons to planar magnetic headphones. The pros and cons are summed up in the following table:
|Low distortion||Difficult frequency damping/tuning|
|Easily driven by amplifiers||Heavy|
|Accurate transient and bass response||Bit expensive|
|Large diaphragm with planar sound wavefront||Fewer options|
Let's go over each pro and con in a bit more detail:
Pros Of Planar Magnetic Headphones
The conductor in a planar magnetic driver is designed, practically speaking, over the entire area of the diaphragm. This causes the entire diaphragm to move uniformly, which yields excellent audio reproduction even at high levels.
Conversely, moving-coil dynamic diaphragms are moved by a coil in their centre that does not extend over the entire area. This causes non-linearities when the coil is set to move at greater amplitudes.
Easily Driven By Amplifiers
The flat serpentine nature of the planar magnetic conductor yields an impedance that is nearly purely resistive. The flatness of the impedance graph means that amplifiers (if they have a low output impedance) can easily drive the planar magnetic headphones.
Planar magnetic headphones may require amplifiers to boost the voltage and current of the audio signal to achieve appropriate listening levels. However, these amplifiers will have an easy time driving the planar magnetic drivers.
Headphone impedance is a deep and complex top. To learn more, check out my article The Complete Guide To Understanding Headphone Impedance.
For more info on headphone amplifiers, check out my article What Is A Headphone Amplifier & Are Headphone Amps Worth It?
Accurate Transient Response
Audio transients are the short-lived peaks in an audio signal. Obvious examples include snare and kick drum hits.
Transient response refers to the accuracy in which a headphone's driver can recreate the transients of the audio signal as sound waves.
This is, again, due to the conductor being spread out across the entire diaphragm. The input signal pushes and pulls the entire area of the diaphragm.
This yields an incredible transient response and a tight bass response, which is critical for most music.
Large Diaphragm With Planar Sound Wavefront
As previously mentioned, the planar magnetic driver produces a planar sound wavefront. These wavefronts are more natural to the ears. So even though the drivers are in close proximity to our ears, they sound more natural and may even give a sense of a wider, clearer stereo image.
Cons Of Planar Magnetic Headphones
Difficult Frequency Damping/Tuning
The large magnetic structures to either side of the diaphragm will naturally repel each other with a rather strong magnetic force. Heavy-duty housing is required to keep these magnets in close proximity.
This housing causes resonance frequencies that must be tuned out. Air volumes between the diaphragm and the magnets cause issues with the frequency response that must be taken into account.
Planar magnetic headphone manufacturers must take all these considerations into account, and damp/tune the headphones to achieve a reasonable frequency response.
Damping materials may wear over time and alter the response of the headphones.
For more information on headphone frequency response, check out my article What Is Headphone Frequency Response & What Is A Good Range?
The relatively heavy magnetic arrays and the housing required to hold them in place adds notable weight to planar magnetic headphones.
From the materials to the rather in-depth design process, planar magnetic headphones are not cheaply made. This is reflected in the price.
Lower-end planar magnetic headphones may run a couple of hundred dollars USD, while the high-end models have prices points of several thousand dollars.
Though perhaps not a huge con, there are relatively few options on the market when it comes to choosing a pair of planar magnetic headphones.
We'll get to the brands/manufacturers that design and build planar magnetic headphones in the section titled Planar Magnetic Headphone Brands.
Planar Magnetic Headphone Examples
Now that we understand how planar magnetic headphones work let's have a look at a few examples.
The Hifiman Sundara (link to check the price at B&H Photo/Video) is a mid-range pair of planar magnetic headphones.
The Hifiman Sundara is featured in My New Microphone's Top 5 Best Open-Back Headphones Under $500.
These mid-range open-back circumaural headphones are easily powered from a wide variety of audio sources, including smartphones, moderate-power desktop amplifiers, portable digital audio players, and more. They are perfectly suitable for home and mobile use.
- Frequency response: 6 Hz – 75 kHz
- Sensitivity: 94 dB SPL/mW
- Impedance: 37 Ω
The Audeze LCD-X (link to check the price on Amazon) is a pair of higher-end planar magnetic headphones.
The Audeze LCD-X is featured in My New Microphone's Top 5 Best Planar Magnetic Headphones.
Audeze is featured in My New Microphone's Top 13 Best Headphone Brands In The World.
These high-end open-back circumaural reference planar magnetic headphones are designed for professional mixing, mastering, and reference level personal Hi-Fi listening. They are suitable to be driven by low-powered external headphone amplifiers and portable devices alike.
- Frequency response: 5 Hz – 20 kHz
- Sensitivity: 103 dB SPL/mW
- Impedance: 20 Ω
Audeze iSINE 10
The Audeze iSINE 10 (link to check the price on Amazon) is a pair of planar magnetic earphones.
These semi-open planar magnetic earphones feature large 30mm drivers. They are designed to deliver an immersive audio experience with audio devices such as CD players, recorders in VR environments for gaming, and other applications.
- Frequency response: 10 Hz – 50 kHz
- Sensitivity: 110 dB SPL/mW
- Impedance: 16 Ω
The Hifiman Susvara (link to check the price at B&H Photo/Video) is a high-end pair of planar magnetic headphones.
The Hifiman Susvara is featured in My New Microphone's Top 5 Best Planar Magnetic Headphones.
These top-of-the-line open-back circumaural headphones use “Stealth Magnet” technology to provide an acoustically transparent sound without interference from reflections and diffractions.
- Frequency response: 6 Hz – 75 kHz
- Sensitivity: 83 dB SPL/mW
- Impedance: 60 Ω
Planar Magnetic Headphone Brands
Note that there are many more companies that produce planar magnetic headphones. However, Hifiman and Audeze are the standout brands that produce these types of headphones.
To read more about the best headphone brands on the market, check out My New Microphone's Top 13 Best Headphone Brands In The World.
Other brands that manufacture planar magnetic headphones include:
- Dan Clark Audio (formerly MrSpeakers)
- Monolith by Monoprice
- Advanced Sound Group
Do headphones need burn-in? No, headphones do not require a period of “burn-in” time. Although it's true that headphone drivers and housings will lose rigidity over time, this loss of rigidity will not result in a measurable increase in performance. If anything, the loosening of the headphone components over time will lead to worse performance further from the intended sound.
Are expensive headphones worth it? The best headphones on the market today are often the most expensive. However, in my opinion, there's no reason to spend a fortune on headphones if they're out of your budget and you can get professional results at a fraction of the price.
For a detailed discussion on determining whether headphones are worth the price to you, check out my article Are Expensive Headphones (Or Cheap Headphones) Worth It?
Choosing the right headphones or earphones for your applications and budget can be a challenging task. For this reason, I've created My New Microphone's Comprehensive Headphones/Earphones Buyer's Guide. Check it out for help in determining your next headphones/earphones purchase.