What type of magnet is in a speaker

Nd-Fe-B are now ubiquitous. Those tiny fridge magnets capable of holding several times their mass are often neodymium alloys. Of all magnetic materials usually considered for loudspeakers, this alloy has the biggest magnetic punch in its weight class. Its ratio of magnetic field strength vs. Similarly, closed magnetic circuit designs provide the low leakage with an even smaller footprint, where space is at a premium.

One of the limitations of rare earth materials is their relatively low Curie point. One option is a samarium-cobalt Sm-Co alloy. The key factor is the rather expensive cobalt, which provides magnetic stability at higher temperatures — one of the factors providing Al-Ni-Co alloys the with the highest Curie point. While this is the costliest magnetic material, its across-the-board performance relative magnet strength, corrosion resistance, and operating temperature make it worthy of consideration under more extreme operating conditions.

Have questions? Let us help. We are your source for audio solutions. Email: contact Stetron. Customer Service: Canada: U. A basic cross-sectional diagram of a planar magnetic loudspeaker is shown below with the appropriate magnetic field lines:.

As we can see, there are magnet arrays to either side of a movable diaphragm. The magnetic field strength is concentrated at the diaphragm. This varying magnetic field interacts with the permanent field of the magnetic arrays. It causes the diaphragm to move and produce sound in accordance with the waveform of the applied audio signal.

Note that the magnetic arrays used in magnetostatic loudspeaker drivers have space between their carefully positioned magnets.

The planar magnetic driver design also extends to headphones. With the ribbon driver, we have a magnetic structure with opposite magnetic poles to the left and right of the ribbon rather than to the front and back like the aforementioned planar magnetic driver. These magnets must be very powerful to provide the magnetic field strength required to move the ribbon effectively.

The ribbon itself is made of a conductive material and is often corrugated to improve durability and efficiency. The extreme thinness and low mass of the ribbon allow it to move very accurately. However, strong permanent magnets are required to produce a decent level of sound.

As the audio signal passes through the conductive ribbon, a voltage is applied across the ribbon, producing a varying magnetic field.

The moving-iron loudspeaker was the first effective electromagnetic loudspeaker design. Today, the design is pretty well relegated to balanced armature headphone drivers, but this driver type is still worth mentioning.

In the driver above, the magnets are placed above and below a conductive armature that is physically balanced in a system. The audio signal is passed through a stationary coil which causes a varying magnetic field in the coil. This field is then extended to the armature, which causes it to move between the two magnets.

As the armature moves, the mechanically coupled diaphragm moves and produces sound directly proportionate to the audio signal. The magnetostrictive speaker design is much less known than the above-mentioned driver designs.

However, it uses magnets and, therefore, should be mentioned in this article. As the name would suggest, the magnetostrictive driver work on the principle of magnetostriction. Magnetostriction is a property of ferromagnetic materials that causes them to change their shape during the process of magnetization. So as the audio signal is passed through the stationary coil, a varying magnetic field is extended to the magnetostriction core.

As the plates experience a varying magnetic field, they change shape ever-so-slightly in shape and move a diaphragm that propagates sound waves. When the coil is not experiencing an audio signal, the core and its magnets return to their original shape.

Neodymium magnets are the strongest kind of permanent magnet available. They were invented in the s and have since become standard in high-quality electromagnetic audio transducers headphones, microphones and, of course, loudspeakers. They produce very strong magnetic fields and weigh considerably less than other magnets.

To further improve upon their performance, Neodymium magnets are coated with nickel or resilient plastic to improve durability and resistance to corrosion or rust.

Of course, not all electromagnetic loudspeakers have top-of-the-line Neodymium magnets. Other headphone magnet materials that also perform well include:. When the signal current passes through, the two armature will push each other for different magnetic flux.

Unlike electromagnetism, inductance can regenerate lower frequencies, but its efficiency is very low. Usually, plastic diaphragms are vacuum vaporized with inductive materials such as aluminum. Two diaphragms are placed face to face. When one of the diaphragms is added with positive current and high voltage, the other one will induce a small current, and the sound can be produced by attracting and repelling each other. Because of its lightweight and small vibration dispersion, electrostatic monomers are easy to get clear and transparent treble, fail to catch bass power, and its efficiency is not high.

It is easy to collect dust by using DC electrodes. At present, manufacturers such as Martin-Logan have successfully developed a hybrid speaker with electrostatic and movable coils, which solves the problem of insufficient bass of electrostatic body and is widely used in headphones. However, the cone basin vibration membrane is changed into the plane vibration membrane of a honeycomb structure.

Because of the empty effect of fewer people, the characteristics are better, but the efficiency is also low.

Without the traditional voice coil design, the diaphragm is made of very thin metal, and the current flows directly into the channel body to make it vibrate and pronounce. Because its diaphragm is a voice coil, it has very light mass, excellent transient response, and good high-frequency response.

However, the efficiency and low impedance of ribbon horns have always been a great challenge to the expander, and Apogee can be a representative. Another way is to have a voice coil but to print the voice coil directly on the plastic sheet, which can solve the problem of the partial low impedance, Magnepang is a leader in this kind of design. The diaphragm drives the air at the bottom of the horn, which is very efficient because the sound is not diffused during transmission.

But because the shape and length of the horn will affect the timbre, it is not easy to reproduce the low frequency. Now it is mostly used in giant PA systems or high-pitched monomers.

American Klipsch is an old horn manufacturer. There are other improved ribbon design developed by Dr. Haier in , called Haier horn, which is very excellent in theory, but few users in Taiwan.