March 01, 2019
Planar Magnetic Technology - you may have heard of it. It’s been around for decades, long before it was adapted for use in headphones, and there’s an abundance of information available online. There’s so much information, in fact, that achieving a comprehensive understanding of what the technology is, and why you should care, can be a little challenging.
If this applies to you, then consider this article a starting point. Here we’ll discuss the limitations of more conventional headphone driver designs and how Audeze’s planar magnetic drivers overcome those limitations.
Most headphones use inexpensive, mass-produced dynamic cone drivers. These drivers are available in standard sizes from just a few manufacturers and can be selected and rebranded based on the needs of the individual headphone company. Because this technology is relatively cheap and readily available, it’s a good option for those headphone companies looking to sell a lot of headphones at low cost. However, dynamic cone drivers have serious inherent design limitations which means that what you’re saving in money, you’re losing in audio quality.
Dynamic drivers are usually activated by a voice coil that’s attached near the center of a diaphragm - most often a paper, plastic or metal cone. As electrical current is passed through the voice coil, force is exerted at the center of the diaphragm, causing it to move. This is what produces the sound you hear.
Ideally, the entire diaphragm would move in unison. However, because the driving force begins in the center and must travel outward, not all parts of the diaphragm begin moving at the same time. This results in breakup modes, mechanical filtering, transmission delay and local resonances, which cause audible, measurable distortion and loss of resolution - especially at higher volumes.
Why do breakups occur and what are they? As mentioned, an ideal diaphragm should move in a perfect pistonic motion, with all points on the diaphragm moving in unison. Breakup occurs when the forces acting on the diaphragm compromise its structural integrity, causing different points on the surface to begin moving out of sync. This is one of the first challenges addressed by Audeze’s planar magnetic technology.
While more detailed information about how we address this challenge can be found in our Diaphragms article, the key point here is that Audeze’s planar magnetic drivers are able to produce uniform driving force directly across the entire diaphragm. This allows the diaphragm to move in a nearly perfect pistonic fashion, resulting in low distortion across the entire frequency spectrum.
Who doesn’t love some deep, powerful, tight bass? Good bass reproduction requires effortlessly moving large volumes of air. This is best achieved with a diaphragm featuring a large surface area and a high degree of flexibility. Surface area determines the volume of air that can be displaced while flexibility allows for the effective reproduction of low frequencies.
Dynamic drivers are relatively small and include stiff diaphragms. In order to move the large volumes of air required to reproduce low frequencies under such circumstances, these drivers must undergo large excursions. This subjects them to extreme forces which can lead to distortion and even damage at high volumes.
Audeze’s planar magnetic drivers feature some of the largest and most flexible diaphragms in the business. As a result, our drivers are able to move very large volumes of air with a fluid range of motion. This allows them to produce extremely clean and deep bass that vastly outperforms any other headphones out there.
Due to the small diaphragms of cone drivers, not only are those diaphragms subject to breakup modes, but the pressure wave that’s made with each motion of the diaphragm also tends to be sphere shaped. Our brains interpret the spherical shape of these pressure waves as distorted or unnatural. This makes it difficult for us to form a convincing mental image of the sounds and their placement in space, also called stereo imaging. A flat, or planar wavefront is more natural for our brain to perceive and leads to a more pleasant listening experience with accurate sound localization. Audeze’s large planar drivers produce a planar wavefront that results in imaging that puts you right in the music...
Sound waves are extremely complex. Every sound heard in a good recording, from the loudest cymbal crash to the faintest creak of a piano bench, is represented in a tumultuous pressure wave. For an immersive and realistic listening experience, the driver needs to be able to reproduce that wave faithfully, without missing any of the details. Like a sports car, the diaphragm needs to be nimble, have excellent control, and be able to accelerate and change direction on a dime.
The laws of physics governing this are pretty simple: Force = Mass x Acceleration. Acceleration defines the diaphragm’s ability to move rapidly. If the diaphragm has lower mass, it can have a much higher acceleration for the same force. Dynamic drivers use diaphragms that are orders of magnitude heavier and thicker than the ultra-light and thin diaphragms used in our planar magnetic drivers. As a result of their higher mass, dynamic drivers are simply not capable of accelerating as fast, or being as nimble as the planar drivers made by Audeze. The mass of the diaphragm used in dynamic drivers fundamentally limits their sonic performance, their ability to resolve and reveal details, and their transparency.
One of the key pieces of hardware (after headphones of course) in a high-end audio chain is the amplifier. Amplifiers can be a bear of a topic, and there’s a ton of information about thehowsandwhysthat you can read in our Amplifier power article. A key topic covered in that article is impedance -- basically put, impedance is the measure of the drivers’ resistance to the current being supplied by the amplifier.
When it comes to impedance characteristics, planar magnetic drivers are, once again, different from dynamic cone drivers. Because of the construction of a dynamic driver, it’s what’s called an inductive load. This means that a dynamic voice coil is going to resist the current going through it differently depending on the frequency, resulting in poor control over the movement of the diaphragm. Audeze’s planar magnetic drivers don’t suffer from this variation in impedance. Because the voice coil is printed directly on the diaphragm, they produce a “flat” impedance curve (since they’re a purely resistive load). This means that there is no change in resistance regardless of the frequency, offering a huge boost in control and resolution compared to a dynamic driver. This means our headphones perform better on more types of amps, making your amp/headphone selection that much easier.
Planar magnetic headphones rock. When made properly, they have vanishingly low distortion, lightning fast transient response, and wide, accurate frequency response. Audeze makes the best planar magnetic headphones in the world, with multiple patents and technological breakthroughs which no one else can claim. The advancements in technology you’ll find in every single pair of Audeze headphones makes them something truly special, and audiophiles and professionals the world over are hearing the difference. We’re always striving for excellence and innovation, and are constantly evolving in order to further our craft. Uncompromised Audio isn’t just a slogan, we truly believe in it, because we’re as passionate about audio as you are.