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beyerdynamic reinvents headphones. With Tesla technology, the borders of feasible technology are reached

All technology has its physical limits. The automotive industry is struggling with the effective range of electric vehicles as manufacturers of solar cells are looking for greater efficiency in the generation of electrical power. For headphone developers, the challenge is in the magnetic field of sound generation. To put it more precisely: at the magical frontier of 1 tesla.

Scientists define tesla as the unit of magnetic induction or magnetic flux density in the metre-kilogram-second system (SI) of physical units and it was not until 1960 that it was named after the electrical engineer Nikola Tesla. Born in 1856 in present-day Croatia, Tesla is seen as being the grandfather of modern energy generation. With his alternating-current inventions, he made long-distance electrical power transmission possible. The fact that he is hardly known, whilst his contemporary and professional opponent Thomas Alva Edison enjoys the highest esteem, is connected with Tesla’s self-imposed objectives. Rather than commercial success, it was finding answers to ostensibly insoluble problems that fascinated him. Thus he experimented early with the wireless transfer of energy and transmitted Morse code by wireless over many kilometres years before Guglielmo Marconi Peace Prize for the invention of wireless telegraphy.  

The pioneering spirit of Nikola Tesla also inspired beyerdynamic developers when it was a question of revolutionising one of the Heilbronn audio specialists core products: the headphone. The tesla unit presented them with a daily challenge, since values in excess of 1 tesla are deemed to be difficult to achieve in the construction of headphones. Here, every increase of the so-called flux density can provide immense advantages. The voice coils can be more filigreed and consequently react more quickly, while the sound generated gains precision and richness in detail. At the same time, the energy utilisation increases and the listener can play louder. 

With its T 1 high-end headphones, beyerdynamic succeeded at the end of last year in achieving what many considered to be impossible: a quantum leap in terms of sound quality and audiophile sound processing. A full series of “Made in Germany” constructive measures and engineering developments provided the T 1 with a magnetic flux density of 1.2 teslas. This was over twice as much as that of previous top-of-the-range models from Heilbronn and reason enough for beyerdynamic to name the technology used after the ingenious visionary and inventor. 

With the T 50 p headphones,  conceived for mobile operation, the tesla innovations of the T 1, current winner of the red dot design award 2010, are being adopted for other models. Mario Gebhardt, Head of Development for audio products at beyerdynamic, explains the special technical aspects of the new type of headphone construction. 

What does the term ‘Tesla technology’ actually mean?

Mario Gebhardt: In beyerdynamic headphones, “Tesla” stands for our latest system technology that is distinguished by a very powerful magnetic drive and clean reproduction with a low degree of total harmonic distortion. 

What are the advantages of the strong magnetic drive?

Gebhardt: It can be used to design the voice coil that generates the sound more filigreed. This where the sound benefits in gaining extreme richness of detail. On the other hand, the additional magnetic power can be converted into acoustic energy, giving the reproduction more power and impact.  

So you gain additional leeway in development?

Gebhardt: Exactly. In the T 1, we take advantage of the magnetic power so that we can use a very filigree and detail-rich 600 ohm coil, without any loss in efficiency. But with the T 50 p (available end of mai), a low-resistance 32 ohm coil converts as much magnetic power as possible into acoustic energy. In this way, we have an ideal partner for mobile devices with low output power.  

Is too much sound volume damaging to the hearing?

Gebhardt: Certainly, but every device has a volume control and you do not have to listen at top volume. The good thing about a high level of efficiency is that it is also effective at lower volume levels, providing a finer and detail-rich sound, which means that you do not have to turn up the volume so high in order to hear properly. 

How did you achieve the higher magnetic power?

Gebhardt: In principle, it was a question of designing a system that permitted the lowest possible degree of loss in magnetic flux. We achieved this with a new type of system geometry that permits us to transfer the magnetic force optimally to the voice coil. Previously, a neodymium magnet was used at the centre of the system, and its size was naturally limited inside the headphones. With the Tesla principle, the magnet is mounted as a ring encircling the coil and this enables us to divert more energy to the membrane, which is where it is required. 

Can the powerful magnetic field lead to health problems?

Gebhardt: No. The strength of the magnetic field in a headphone system should not be confused with electromagnetic radiation. Inside the headphones, there is a static magnetic field, similar to the earth’s magnetic field, which is also concentrated upon a tightly limited area: the air gap with the voice coil. 

And none of this magnetic field penetrates outside?

Gebhardt: Our Tesla systems are indeed optimised so that as little magnetic power as possible escapes from the system, because this would be a loss in efficiency. Naturally, audio signals in the voice coil generate a tiny degree of electromagnetic radiation, as is the case with all headphones. But this is lower than with conventional systems anyway, because the high degree of efficiency requires a very small level of power.  

What accounts for the particularly clean sound?

Gebhardt: It is the result of many details. What should be specially mentioned is the ring-shaped magnet, that permits positioning a central drilling immediately behind the centre of the membrane in order to minimise discolouring resonances. Apart from that, we use a special multi-level membrane that effectively suppresses unwanted break-up vibrations and consequent distortion. 

What else is it that particularly distinguishes the Tesla headphones?

Gebhardt: The particular highlight of Tesla technology is the design as a full metal system. It prevents any uncontrolled resonation by parts of the casing leading to distortion of the sound. Apart from that, the metal shields the construction from electrical disturbance fields. In a Tesla headphone, the only thing that causes the membrane to emit sound is the musical signal itself.