Why Do Speakers Have Magnets?

By José Carter  |  August 8, 2021
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José Carter
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José is a veteran audiophile with an MSc in Engineering, and a passion for sharing his audio knowledge with others.
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Speakers are the most vital component of any sound system, and they also have the added benefit of being your neighbors’ worst nightmare. The technology that goes into making speakers has improved significantly over the last decade.

However, the fundamental principles of how a speaker works haven't changed much since Alexander Graham Bell patented his first electric loudspeaker back in 1876. To better understand how they function, we need to explore their most important component—the magnet.

So, why do speakers really have magnets and what are the functions of these? Let's find out more below by diving into this topic.

Why Are There Magnets In Speakers?

There are speakers in magnets because when an electric current is passed through the wire on either side of it, it creates a magnetic field - letting the voice coil move freely back and forth, which creates sound waves that you then hear with your ears.

This is because a speaker is a type of device called a transducer. It transforms electrical energy into sound energy. But for it to be able to do this, it requires magnets.

So, why are the functions of magnets in speakers? Before answering this question, we first need to understand which two kinds of magnets you find inside a speaker.

Illustration of a speaker with cut out sections.
Image 1: The various parts of a speaker that work together to produce sound.

Permanent Magnet

This type of magnet is fixed into a speaker when it's assembled.

Electromagnet / Voice Coil

This magnet is created by passing a current through the voice coil of your speaker. This coil of wire is found suspended in the circular gap between the poles of the permanent magnet.

Why Are These Magnets Used In Speakers

Sound is a result of the displacement of air. So what a speaker does is that it pushes and pulls the surrounding air creating changes in pressure. These changes are then carried through the air, and your brain interprets them as sound or even music. So let’s take a closer look at how this happens.

Well, a speaker usually has a cone and with a permanent magnet attached to it. The voice coil is then placed near the magnet to still allow the magnet to move freely without making contact with the coil.

Diagram showing how speakers work.
Image 2: A simple illustrative diagram that shows how speakers work.

When a current passes through the coil, a magnetic field is created, and the changes in that field cause the magnet to move. The magnetic field produced by the voice coil can either have north or south polarity depending on which direction the current is flowing. If you reverse the current, you will also change the polarity of the electromagnet. You can also alter the strength of the magnetic field by altering the current flowing through the coil.

When a current flows through the voice coil, the polarity direction of its magnetic field rapidly changes. This simply means that the electromagnet will either be attracted to or repelled by the permanent magnet, which moves it and the cone back and forth. As a result, the cone amplifies the vibrations produced by the movement of the voice coil, pushing sound waves out of the speaker into the air, which in turn creates sound.

To produce the different frequencies required for the music we consume, some speakers usually have cones of various sizes which are dedicated to high, medium, and low pitches.

Why Are Magnets Built Inside Speakers?

They are built inside the speaker because permanent magnets generate a consistent magnetic field necessary to create sound. While a voice coil only produces a magnetic field once a current passes through it.

Image of different speaker types.
Image 3: Comparison between 3 different types of speaker magnets that exist.

There are three kinds of magnets used in speakers, and they all have different effects on how the speaker functions.

Neodymium Magnets

One of the biggest advantages neodymium magnets have more than other types of magnets is their weight and efficiency. Neodymium speakers weigh around 50 percent less than other speakers without any compromise in quality.

Neodymium is a rare earth element with unique characteristics that make it ideal for use in making speakers. Its lightweight composition allows it to be a very effective material in both small and large systems.

Alnico Magnets

Originally, speakers were made from a material known as alnico. It is a combination of aluminum, nickel, and cobalt. Alnico gets its name from its respective atomic symbols, Al, Ni, and Co.

Nowadays, cobalt is a scarce resource and therefore expensive to produce. This means that the cost of making alnico speakers is very high. However, many musicians still prefer them because they sound warmer and sweeter at lower volumes than other types of speakers. In addition, alnico magnets are ideal for smaller systems/speakers.

Ferrite / Ceramic Magnets

Compared to Alnico magnets, ceramic magnets are much cheaper to make. They're also more versatile and can produce a broader range of tones. However, these kinds of speakers weigh considerably more. This allows them to handle more power, and they usually sound better at higher volumes than other magnets. Therefore, they’re more likely to be used to make loudspeakers.

Do All Speakers Use Magnets?

Almost all speakers contain magnets.

However, there is a special kind of speaker known as an electrostatic speaker, which does not. These types of speakers use very high voltages instead of magnets. However, electrostatic magnets are very expensive and very hard to find.

The quality of your speakers' magnets can also impact how long they will last, and how quiet your speakers will be.

Speaker & Magnet Size Vs. Quality

We've examined the role of magnets in speakers and how they produce sound. So, would simply using a bigger magnet improve a speaker? Well, in short, yes and no.

Since magnets produce magnetic fields, which create the vibrations necessary to produce sound, we can deduce that a bigger magnet will produce more vibrations simply because it creates a stronger opposing magnetic field.

And more vibration would result in louder sound, but there are exceptions to this rule.

A speaker needs more than just a magnet to produce high-quality sound. Having a big magnet doesn't necessarily mean that it will produce the best sound quality. There are a lot of factors that you still need to take into account. A speaker is only one part of the equation.

Conclusion: Speakers & Magnets

In this article, we first explained what a speaker is and what it does. We then took a closer look at why speakers have magnets and what those magnets are.

We took a look at the parts of the speakers responsible for creating sound and how they work together to achieve this.

We learned what happens when a current passes through the voice coil and how that results in the movement of the magnet. We also looked at how the polarity and strength of the voice coil change when we alter the current.

We then learned how the cone amplifies the vibrations produced by the movement of the voice coil, pushing sound waves out of the speaker into the air, creating sound.

José Carter
Founder
José is a veteran audiophile with an MSc in Engineering, and a passion for sharing his audio knowledge with others.
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