Sunday, December 4, 2022

3 most exotic headphone designs: electrostatic, magneplanar, bone conduction


The popularity of headphones as a device has grown significantly in recent years. If earlier high-quality headphones were produced mainly by companies specializing in audio equipment, today even for such giants as Apple and Samsung, having several models of good headphones in their assortment is a matter of prestige. This is not to mention smaller companies that are trying to popularize technological solutions in the mass market, which were previously known only to one and a half audiophiles. This article will talk about modern types of headphone design, their advantages and disadvantages.

How are conventional dynamic headphones arranged?

Everyone has these. They first appeared in 1937 – it was the Beyerdynamic DT-48 model, which, by the way, is still being produced in a modern revision. In this design, the sound is emitted by a small speaker, consisting of a moving magnetic coil, a magnet and a membrane (diffuser). The magnetic field moves the speaker membrane, which vibrates the air and propagates sound waves through the air. The main advantages of this design:

they are easy to produce;
you can make very inexpensive models thanks to a simple process technology and available materials;
if you try and make a high-quality driver, then it will sound very good, although the price in this case increases tenfold.
1937 Beyerdynamic DT-48

The problem is that this design is already a hundred years old at lunch, so it is not without flaws. To understand them, you need to understand how the speaker emits both low and high sound at the same time. Some might think that the membrane moves forward and emits a high note, then comes back and emits a low note, but this is not the case. In reality, when moving, for example, forward, the diffuser simultaneously performs thousands of micro-oscillations back and forth, emitting microseconds of a high note and microseconds of a low one.

All this happens so quickly that it seems to the listener to be simultaneous. Of course, with such rapid fluctuations, the quality of the materials is of great importance. The main requirement is for a diffuser – for an ideal result, it must be both infinitely light (so that it moves quickly) and infinitely strong (so that it does not deform when moving, otherwise there will be distortions).

Of course, it is impossible to create an ideal material for such purposes, so engineers always compromise, trying a variety of options – from bituminous paper to Kevlar. However, cone distortion is still the most significant in the audio chain. For comparison, if the distortion of an amplifier or audio card is measured in tenths and hundredths of a percent, then the distortion of a diffuser is measured in tens of percent. The amplitude-frequency response (AFC) of the speaker leaves much to be desired, with humps in one part of the spectrum and dips in the other. Manufacturers have to choose – some headphones play the bass better, some – the middle, etc. But engineers do not sit still and have come up with more advanced types of sound emitters that can be found in modern headphones.

Electrostatic headphones
In 1959, the Japanese company Stax introduced the world’s first electrostatic headphones, the SR-1. In them, the emitter consists of an ultra-thin membrane made of composite material – only a couple of microns thick. The membrane conducts electricity and is located between two perforated metal plates that act as electrodes. Static electricity is applied to them, due to which they create a magnetic field in which the membrane vibrates.

This design has a number of advantages:

an ultrathin membrane weighs orders of magnitude less than the membrane + coil system in a dynamic radiator, and, therefore, oscillates much faster. The sound will be more dynamic, more detailed, the emitter will play out the most subtle nuances of the track;
The frequency response of “electrostats” is much smoother than the frequency response of conventional speakers;
the level of harmonic distortion of electrostats is also much lower. For example, Stax SR-Lambda Professional headphones from 1982 produce only 0.007% distortion around 400 Hz – and this at a concert volume level of 100 dB! This is thirty times less than the best example of a dynamic driver in B&W 800 Diamond acoustics can give out – there is a level of distortion of about 0.5%, and this at a cost of 24 thousand dollars.
This is why electrostatic headphones are considered the holy grail among audiophiles. But not everything is as rosy as it might seem – there are also enough minuses.

Price. Due to the complexity of production, even entry-level models cost thousands of dollars. And Sennheiser has completely released the Orpheus HE-1 electrostatic headphones, which can be purchased for just some four million rubles.
The need for a special amplifier “energizer”. Such headphones cannot be plugged into an ordinary player, because their operation requires currents of thousands of volts. The corresponding amplifier will also cost a couple of thousand dollars.
Bass. For all its splendor, electrostats have their own design flaw and this is the low-frequency component. The fact is that a conventional speaker is better suited to work with a low register – the speakers in subwoofers can overcome up to ten centimeters when moving, which allows you to reproduce ultra-low frequencies. And the membrane in electrostats is sandwiched between two plates, the distance between which is a few millimeters. This, of course, is more critical for speakers than for headphones, but the latter can also disappoint fans of low-end punch.

Headphones Sennheiser Orpheus HE-1 come with an amplifier, but cost like a whole apartment

It turns out that for most people, the benefits of such a solution simply do not justify their price. This is where magneplanars come to the rescue.

Magneplanar headphones
The principle of their operation is similar to electrostats on the contrary: here the current is supplied not to metal plates, in the magnetic field of which the membrane oscillates, but to this membrane itself, sandwiched between two permanent magnets.

Magneplanar emitters are inherently an evolution of electrostatic technology. They have all its advantages – low distortion, flat frequency response and ultra-fast dynamics, while devoid of its main disadvantages:

the production of magneplanar emitters is a little simpler and cheaper than electrostatic ones, and therefore the prices are a little more humane – for example, the cost of some Audeze Mobius Carbon is comparable to the cost of top models of dynamic headphones;
the design eats up low frequencies less;
low-impedance models appear that do not need a powerful amplifier, which makes them even more accessible to the average listener. Models like Oppo PM-1 and PM-3 can be plugged into a regular player.

Audeze Mobius Carbon is one of the most affordable magneplanar headphones, wireless and with a headset

However, magneplanar transducers are still not as fast as electrostatic ones, so audiophiles prefer the latter for ultimate high-end solutions – they are somewhat more dynamic and reproduce the highs better. Also, magneplanars require large permanent magnets to operate, which negatively affects their weight and overall comfort.

Bone conduction headphones
If you return from heaven to earth and look at what is really available to an ordinary listener, then you should pay attention to bone conduction headphones. How it is? The fact is that a person has two ways of perceiving sounds – air, through the auricle, and bone, with the help of the inner ear. For example, when Ludwig van Beethoven said goodbye to the first method (the composer’s habit of dipping his head in a basin of cold water in order to cheer up had an effect), he began to use the second, applying various copper devices to the skull.

These headphones are not attached to the ears, but to the temples. At first, this method of sound perception was used to treat deafness, as well as in the army and sports (for example, among divers). Today it is available to everyone and has many advantages:

security. One of the main advantages of this design. For example, cyclists and drivers can listen to music and hear the traffic perfectly at the same time. Communication with the outside world is not broken;
waterproof. Some manufacturers make bone conduction headphones specifically for swimmers, because they are a one-piece construction with no holes where water can get in;
good sound. Yes, the development of technology has made it possible to create modern devices that not only sound, but sound quite good for their price.
They are arranged quite interestingly. As a basis, they usually use a piezo emitter. A similar one is responsible for beeping from the PC case and is located in many electronic watches. In headphones, it is, of course, more perfect and of high quality. Vibrations from it go to a system of plates that transmit a signal directly to the skull.

AfterShokz headphone design

It sounds quite exotic, but for some it is completely ominous. Many questions immediately arise – but won’t your head hurt from them? Don’t your teeth ache? How do they even feel? Do they pump bass? But here everything is like everywhere else – it depends on the manufacturer and model. For example, today in the mass market the company AfterShokz rules the ball. It produces very interesting models of wireless stereo headphones with decent sound. Of course, this is not an audiophile device, but it is difficult for such a device to find a competitor in its niche. Users assure that these headphones are not a replacement for the usual ones, but an addition to them, because they expand the experience of listening to music and make it possible to enjoy it where it seemed inappropriate before, for example, while talking with friends. Or at work – you can communicate with colleagues and at the same time find out something on the phone.

Bluetooth headset AfterShokz Trekz Titanium blue
As for convenience, here, contrary to expectations, there are solid pluses. They do not press on the temples, and, thanks to their lightweight design, you can easily spend many hours in them. Moreover, the ears do not get tired in them – there are no ear cushions, after all. We can confidently predict a bright future for bone conduction headphones.


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