Magnetic materials

Why magnets used in headphones?

Do you ever think, why do we use magnets in headphones:

As we know, magnetic fields are present around us in one way or the other. In this blog I discussed on how and why we use magnets in headphones and speakers.

Headphones & Speakers are Transducers Device. Electrical energy is converted into mechanical energy in headphones where electrical energy is an audio signal and mechanical energy is a sound wave. This phenomenon occurs by electromagnetic induction where a conductor and magnetic field is required and magnetic field provide by magnets.

How magnets produce sound in headphones? Or how headphones convert electrical energy to sound wave?

When we supply current(AC), we hear the sound wave which is produced as follows: A current creates an electromagnetic field in the coil and electromagnetic field interact with magnetic force which is generated by permanent magnet which pushes the cone outwards and flow of current is opposite direction. The electromagnetic field direction is in reverse. The force on the cone pulls it back in. Repeatedly alternating the current direction makes the cone vibrate in and out. The cone vibrations occur due to pressure variations in the air, which are sound waves.

About the magnets which are used in headphones and speakers:

In today’s era, we all like to use technologically advanced headphone and speakers   which has finest quality of sound. Here so many magnets are available like ferrite, ceramic, aluminum, Samarium Cobalt magnets But  neodymium magnet is best magnet. Neodymium is the strongest type of permanent magnet. It has very light weight. They are approx ten times stronger than ceramic magnets.

Neodymium magnet invented in early 1980. Neodymium magnet has made very advance quality audio and electric motor possible. It is a group of metal magnets made of rare earth metal which makes it to develop strong magnetic field. They are very smaller and lighter than other magnets, this property also making them best for use in earbuds and headphones.  Neodymium magnets are coated by some strong material like nickel or a resilient plastic. This is protecting from corrosion and makes them less brittle.

Nowadays uses of neodymium are endless. Currently they are used in hospital MRI machines, airplanes, boats, cars, speaker systems and earbuds and headphones.  

What are role of magnets in headphones:

Most of the headphones need magnetic field for proper functioning. As discussed above, magnets play very important role in headphones. The headphones are transducer device that turns the electrical audio signals into sound waves for our enjoyment. Generally, most headphone drivers depend on magnets to effectively convert energy.

Basically the role of magnet is to produce a permanent magnetic field that will attract and repulse the electrically charged diaphragm or the conductor that is controlling the diaphragm.

Do all headphones have magnets?

 No, we can say some headphones are work without magnet and electromagnetic induction but majority of headphone use magnets in their drives. Already discussed about headphones those use magnets.

Now question raises that how without headphones are work. They known as electrostatic headphones based on electrostatic principles. The electrostatic headphone has a positively biased (fixed charged) diaphragm that is sandwiched between two perforated metal stators (known as plates), separated by spars. These stators or plates act as capacitor. The biasing voltage required of the diaphragm for make electrostatic headphones active, in short they need power for proper functioning.

When the audio signal is positive, it applies a positive charge on the front plate and an equal but negative charge on the back plate. This is the reason that positively charged diaphragm move to the back. In the other hand, when the audio signal is negative, the front plate becomes negatively charged and pulls the diaphragm while the back plate becomes positive and pushes the diaphragm. In short, electrostatic headphones do not need magnets.

Comparison between electrostatic and magnetic headphones:

If I talk to about comparison then headphones with magnet are more superior over electrostatic headphones, due to strong magnetic force over static electricity. Magnetic drives provide best bass and sound quality over the electrostatic drive.

In this article, briefly discussed above about Why magnets used in headphones? and role of magnets in headphones. Most interesting thing discussed about how audio energy convert in to sound waves and how many type of magnets and which one is best magnet for the headphones and earbuds as well as we discussed about electrostatic headphones and comparison between both electrostatic and electromagnetic headphones.

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K Yashdeep

Hye there..! I am Yashdeep Kamal. I completed my Bachelor in Technology(Materials Science and Metallurgical Engineering). Engineer by passion, writer by choice. I have been writing about Composites, Ceramics, polymers, nanotechnology, advance materials and metallurgy etc. You can read about these topics here. Hope it may help you.

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