Headphones tech: Dynamic vs planar magnetic vs electrostatic

What kind of headphones are for you?

Headphones have become big news over the last couple of years. So big that the greatest name in tech, Apple, decided to buy the biggest name in headphones, Beats, for $3 billion last year. This certainly hasn’t earned Apple monopoly status, though, because there’s more than one way to make a pair of headphones.

We’re going to look at the thee main kinds of headphone driver: the standard dynamic type, the planar magnetic style and the even less common electrostatic to find out whether you should really look into leaving the safe world of dynamic driver headphones.

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How dynamic driver headphones work

If you don’t know what kind of driver your headphones use, they almost certainly have dynamic drivers. This is by far the most common style, and there’s no chance of that changing in the foreseeable future.

They’re also known as moving coil drivers, and are the headphone equivalent of the full-size drivers you probably have in your hi-fi speakers or portable speaker.

In this kind of driver, the signal is sent through a coil of ultra-thin wire, creating a magnetic field that reacts with a magnet that it’s set into. It’s an electromagnetic relationship, in physics terms.

This causes the voice coil to rapidly move backward and forward, in turn moving the speaker diaphragm the coil is attached to. On a hi-fi speaker this is the cone-shaped part you tell the kids not to touch. And they inevitably do. But in headphones or one a small Bluetooth speaker it’ll generally be hidden behind a grille so you can’t see it.

This movement rapidly compresses and decompresses air, causing the sound waves that make up the audio you hear.

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How planar magnetic drivers work

Planar magnetic headphones are much less common than the dynamic kind. In fact, you’ll probably only have heard of a few companies that make them. There are three important names in planar headphones right now: HiFiMAN, Audeze and Oppo. Hardly the biggest names, but worth taking note of if you haven’t already.

These headphones work on a similar principle to dynamic driver headphones: using the interaction of two magnetic fields to cause motion. However, instead of moving the voice coil, pulling the diaphragm in and out from one ring within the driver, here the charged part is spread across the driver, which is a thin, largely flat film.

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So instead of focusing the force on a small part, it’s spread across the diaphragm. This generally requires larger, or more, magnets than a dynamic driver array, and they’re needed on both sides of a diaphragm, which is why a lot of planar magnetic headphones are quite big and heavy.

Headphone veterans out there may also know this kind of headphone as Orthodynamic, a term popularised by Yamaha. However, that’s actually a marketing term that only really referred to Yamaha headphones.

How electrostatic headphones work

Now we’re onto the grandaddy of headphones: electrostatics. Not because they were being worn by caveman back in year X, but because a lot of the greatest headphones ever made use this technology.

The most important maker of electrostatic headphones is Stax, which had its heyday in the ’70s, producing what even now are some of the best headphones you can find. Stax still makes headphones, and there are a few other examples of this highly revered kind of headphone too.

HiFiMAN has announced its own electrostatic pair, which we got to hear almost a year before their announcement back in CES 2013. And what are arguably the best headphones ever made, the £10,000 Sennheiser Orpheus HE90, are also electrostatic.

Other big electrostatic makes over the years include Fostex and Beyer. Electrostatic

So, what’s different? The other two kinds of headphone use middle-men metal conductors to move the driver diaphragm. But here it’s the diaphragm itself that moves directly.

It’s a very thin sheet of electrically charged material, usually made from mylar and just a few microns thick, that sits between two conductive plates. One is positively charged, the other negatively charged. The whole sheet can then be pushed towards either plate, causing the vibration we need to create those sound waves.

You’ll find this kind of driver in some full-size hi-fi speakers too. They’ll generally be paired with a more traditional dynamic driver in its own cabinet to handle the bass, though, or else are absolutely massive, because due to the relatively small amount they’re able to move back and forwards, they don’t excel at creating bass frequencies. This tend to be a bit less of a problem with headphones, though.

What are the pros and cons of dynamic drivers?

The most obvious benefit of dynamic drivers is that they’re cheap. Or at least they can be. They’re effectively a coil of wire (the voice coil) attached to a plastic (in the case of headphones) diaphragm, set into a magnet.

Where trying to make planar or electrostatic drivers on an extreme budget might mean they end up flat-out broken, dynamic drivers can be made for peanuts and still be reasonably effective. They also tend to be a lot easier to drive than planar headphones, because the voice coil construction means there’s less for the driver to actually move. The rest of the diaphragm is simply pulled along.

That works as an introduction to one of the dynamic driver’s big issues, though. As the diaphragm is pushed and pulled only by the part attached to the voice coil, its shape distorts, especially at higher volumes. This can cause audio distortion, too. We’re not talking about crackly fuzz, but simply an altering of the intended sound. You may hear this called “non-linear distortion” in audiophile circles.

On the other hand, dynamic drivers are also very good at creating quite a lot of in-your-face bass, which has become one of the defining characteristics of some of the most popular current headphones, such as the Beats Solo 2.

While considered by some to be an entry-level headphone driver, engineers have been able to pull an awful lot out of this style of driver. Among our favourites are the £1000-ish Sennheiser HD 800: they’re oine of the best pairs of headphones in the world, yet still use a dynamic driver.

What are the pros and cons of planar magnetic drivers?

Planar magnetic headphones are a bit like a middle ground choice between the simple dynamic headphone and the high-end electrostatic one. You get the distortion-reducing even driving force across the diaphragm without needing any extra hardware beyond your headphones and source.

Granted, some planar headphones can’t really be driven properly without a dedicated headphone amp, with some of the HiFiMAN HE-series pairs being good examples of this. But the Oppo PM-1 and PM-3 work well using just a phone or MP3 player.

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The driver design of the planar style also results in very low-distortion sound and excellent transient response. Transient response is how fast the driver reacts to changes in the input signal and how quickly it cuts off those frequencies as they’re cut out of the source, which is particularly important for bass notes.

It’s possible to look too much into these technical terms, though. What we like is that all the planar headphones we’ve tried have very clear, accurate sound that tends to come across as very lifelike.

One slight downside that comes purely from our own impressions of having used a good deal of the planar headphones available in Europe is that most don’t tend to have quite as wide a soundstage as the very widest dynamic headphones. No planar headphones we’ve heard sound as big and wide as the Sennheiser HD 800.

What are the pros and cons of electrostatic headphones?

Some people say you can’t beat electrostatic headphones, and from one perspective we tend to agree. Their architecture lets them create near-flawless detail and very fast ‘attack’.

However, they’re not cheap and they’re not very practical. Sure you can buy an old pair of electrostatics on the cheap if you get lucky on eBay, but you’re unlikely to find a single pair of electrostatics on the high street, let alone an affordable pair.

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For the ultimate experience, you’d want a pair of Stax SR-009 headphones, which cost £3500 before you even buy the required £2000 ‘energiser’ to make them actually work. Because electrostatics don’t work like normal headphones, they need a separate box to function. This is basically an electrostatic-specific amp, but is often called an energiser.

As such, they’re not portable. And electrostatic headphones tend to embrace this. Every pair we’ve used has an open design, meaning the backs of the cups are perforated, letting sound both out and in, but also offering a more open and airy sound.

The best sound we’ve heard from a headphone comes from an electrostatic pair, but then that was the Sennheiser Orpheus HE90, which would cost you about £25,000 once you get hold of the amp too. Oh, and they don’t make them anymore. Want to see what electrostatics sound like in person? Check out the HiFiMAN HE1000 and Stax SR-007/009. If you want to spend less than a thousand pounds your best bet are the AKG K340, available secondhand from eBay for around £350.

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Which is right for you? From a blunt perspective it becomes quite simple. If you want something cheap and easy, the dynamic driver is your only bet. If you have wads of cash to spend and are willing to give up any idea of your headphones being portable or even easy to move about the house, consider an electrostatic pair.

However, in the middle sits the planar magnetic headphone, which is a step-up design that doesn’t mean you have to be willing to sacrifice anything just for the sake of your headphones. They get you some undeniable driver architecture benefits without being a pain in the backside.

The best advice to give when thinking about any serious headphone purchase, though, is to try them if you can. And don’t be too wowed by initial impressions. Try to have a proper listen, if possible.