It’s a common question, which type of magnet is used in speakers? If you are new to the audio world, you have to understand that every speaker, whether small or the most powerful, is designed with a permanent magnet.
The magnet provides a permanent magnetic field for the coil in the speaker. The rapidly alternating direction of the current in the coil also provides an electric field. The interaction of both fields causes the cone to vibrate back and forth.
The pushing and pulling forces help to move the speaker cone rapidly in and out causing vibrations for it to produce sound. This is why speakers have magnets. Speaker magnets are widely used in loudspeakers, speakers, and headphones. Magnets are the key parts of these kinds of these devices.
A Brief History Of Speakers
The earliest speakers were invented in the mid-1800s and didn’t utilize permanent magnets like modern speakers. Instead, they used dual electromagnets as permanent magnets then were too expensive and very heavy.
Speakers using permanent magnets were first invented in 1930 by Jensen. They became popular after world war II when lightweight alnico magnets became widely available.
Speaker manufacturers utilize various types of magnets to suit speakers of different sizes and to achieve a range of tone qualities. Before you tell how strong speaker magnets are, you have to understand the types of speaker magnets. Let’s demystify these types here below.
1. Neodymium Magnets
If you want good sound from a speaker, you need a powerful magnet. Neodymium magnets are the most powerful of the Rare Earth (RE) magnets. When you compare size for size, there is no better-performance magnet out there.
Out of all magnets available, neodymium has the greatest field strength known in the permanent magnet family. Speakers designed with this magnet have a good frequency response because of its sturdy magnet.
This is why neodymium permanent magnets are more often used in medium and high-grade headphones. This use is justified because, with these magnets, speaker tone quality is excellent, sound elasticity is better and the sound field and frequency response is more accurate.
If you plan to use smaller speakers, the smaller the magnets will be used to fit and balance sound production.
Therefore, the level of magnet used depends on the size and weight of the speaker. Neodymium magnets are made with high-fidelity earbuds as they can pack a strong magnetic field into a tiny package.
The most commonly used sizes of neodymium speaker magnets are D50x12mm, D50x10mm, D6x1mm, D6x1.5mm, D6x5mm, D6.5×1.5mm, D6xd2x1.5mm, D12x1.5mm, D12.5×1.2mm and so on.
Best Used For: These magnets are ideal for the miniaturization of tweeter drivers. Even so, they still provide the maximum power density of the magnetic field.
In addition, they can manage temperatures up to +80 degrees C for standard magnets increasing up to +230 degrees C for extreme applications.
These higher-grade magnets can be used in extreme applications for example in cold mines or smelting factories. Because neodymium magnets allow for designing in the highest magnetic fields, they provide the most powerful performance.
Not Great For: The only downside about neodymium magnets is that they shatter the magnets easily.
2. Alnico Magnets
Alnico magnet is used to make original speaker magnets, which is an alloy of aluminum, iron, nickel, and cobalt. Most alnico loudspeakers were used in some of the earlier permanent magnet drivers. The good thing about speakers using Alnico is its tough nature and less prone to cracking than most of the other materials.
But they can sometimes lose their magnetism more readily. Alnico is more expensive than neodymium and ferrite and gives speakers a classic and warm tone.
Best Used For: The great thing about alnico speakers is that they allow for higher performance and reduce demagnetizing effects. In fact, if designed well enough, they can offer a magnetic field that can perform as well as neodymium magnets (but with greater axial length)
The greatest advantage of these speakers is that they are very easy to magnetize. They are also easy to weaken which can allow for precision tuning. This then allows for better tuning and optimum acoustic performance.
In terms of temperature resistance, the speakers allow for great resistance regardless of temperature variations. As such, you can achieve consistent performance within a wide temperature range.
These speakers also have better corrosion resistance than neodymium.
Since these magnets offer such great properties, why are neodymium magnets so much more popular? Well, neodymium magnets are mostly used for regular speaker applications while alnico speakers are mostly used in precision drivers and external applications such as horns.
Not Great For: Sometimes for maximum performance, alnico speakers must be tapered.
3. Samarium Cobalt Magnets
This type is used less often by manufacturers due to its high cost. It has most of the strength of neodymium and has great heat resistance.
Samarium magnet tends to be as brittle as neodymium but can withstand corrosion and moisture.
Best Used For: Samarium Cobalt magnets are much better at maintaining a steady output in the magnetic field with temperature variations.
Only alnico magnets offer better consistency in magnetism over a temperature range. They also offer better corrosion resistance compared to neodymium magnets.
In general, Samarium Cobalt magnets are mostly used to create drivers that are used in special applications such as extreme hot and cold environments or even marine environments. They are also used when precision output is required such as sound measuring applications e.g testing decibels.
Not Great For: The main disadvantage here is cost. These magnets are are more expensive than neodymium.
Samarium Cobalt is also a weaker form of Rare Earth magnets when compared to neodymium.
Their corrosion resistance is not as good as ferrite magnets.
4. Ferrite or Ceramic Magnets
This type of magnet may be considered the cheap type and cracks more easily than a metal type of magnet.
They maintain their magnetic strength well over time, provided you do not bring a stronger neodymium magnet near it.
Their weight makes the speaker system to be heavier, which is a drawback for portable guitar amplifiers and portable speakers. This is why they are mostly used in the larger drivers for mid-range to high-range, woofers and subwoofers.
Speakers that are designed using ferrite magnets tend to sound better when played louder. However, ferrites don’t perform as well as neodymium. In fact, since neodymium magnets are lighter, they normally replace larger and heavy ferrite magnets in some applications gradually.
Best Used For: Ferrite magnets offer excellent performance in damp conditions because they are corrosion-resistant by nature. This makes them ideal in marine sounder applications.
These speakers are low cost which means they can be produced in large quantities economically.
In general, these ferrite speakers are used where longevity and low cost are more important.
Not Great For: Ferrites tend to be quite large and so can only be used with bulky driver assemblies.
5. Bonded Magnets
Bonded magnets are compression-bonded and injection-molded magnets that are produced by processing a specific combination of elements.
This results in a metal that has specific magnetic characteristics. These magnets are developed by mixing the magnetic powder with a binder (plastic, resin, etc). This then creates lower-power magnetic materials.
The advantage here is that the magnets can be mass-produced easily with good tolerances. These magnets are rarely used in speakers, but in a few cases, you can find them in lower-grade speakers made for simple applications.
They are mainly used in motors and sensors which are used in a range of products. This includes toys, computers, office equipment, and more.
Best Used For: Bonded Magnets can be mass-produced easily with good tolerances.
They can also be molded into complex shapes and also molded directly onto various components.
Not Great For: The metal is not pure and so may not be great for certain applications.
What Type Of Magnets Are In Speakers?
Neodymium magnet is a commonly used permanent magnet in speakers because of high magnetization and demagnetization, and small size. electromagnet, which will deform the cone more and produce more sound. It has the greatest field strength of any permanent magnet known. Speakers made with these magnets have good frequency response, and because the magnets are strong, you can use smaller magnets, reducing speaker size and weight.
Does A Bigger Magnet Mean A Better Speaker?
The bigger the magnet, the stronger the potential driving force of the speaker (assuming the magnetic strength of the magnet is constant). Small magnets are for small speakers and produce, by nature, “weaker sound”, while bigger magnets make bigger speakers capable of producing louder sound.
How Long Do Speaker Magnets Last?
This depends on the type of magnet. A temporary magnet can lose its magnetization in less than 1 hour. Neodymium magnets lose less than 1% of their strength over 10 years. Permanent magnets such as sintered Nd-Fe-B magnets remain magnetized indefinitely.
Conclusion
So which type of magnet is used in speakers? It all depends on the intended use of a speaker, it will be built with a certain size and intended power which dictates the type of magnet used.
Some magnets are cheaper and not as durable while others are more expensive, more durable and more powerful. Speaker manufacturers are always careful in deciding the type of magnet to use for specific speakers.