It causes the coils to alternately attract and repel one another. One of the coils receives an excitation signal directly from the source. While the other coil receives the source signal in an indirect way, preferable via a bridge rectifier.
The coils may be in the form of conventional wound wires. Or it can be formed on a printed circuit board in the form of flat spirals. The resulting speaker is very lightweight. It is well suited for use in cars, aeroplanes, and other optimizations in which weight minimization is important. There are other speakers which do not use magnets at all. For instance, Piezo speakers. Piezo speakers use the piezoelectric effect. They are similar to the above-mentioned process. They generate mechanical vibration by applying an electrical signal to a piezoelectric crystal.
Buzzers in wristwatches generally use piezo speakers. Magnets are used to make an opposing magnetic field which creates vibrations. This makes the cone or panel of the speaker move. The vibrations are the sounds we hear. As a convention, speakers generally contain large magnets inside of them.
Bigger magnet means more vibrations. Because a larger magnet would imply stronger opposing magnetic field leading to more vibrations. There are many other factors which are involved. This is especially true with the growing popularity of super lightweight and powerful magnets. These magnets are generally made of neodymium.
As we have already seen, neodymium magnets are really powerful although they are small and lightweight. In this segment we saw the role of magnets in speakers. We saw that the sound is produced by the interaction of two magnetic fields.
At least one of the two magnetic fields is the result of an electromagnet. To convert an electrical signal to an audible sound, speakers contain an electromagnet. It is a metal coil which creates a magnetic field when an electric current flows through it.
The electrified coil has the properties of a normal permanent magnet. There is, however, one particularly handy property. When the direction of the current in the coil is reversed, the poles in the magnet gets flipped.
This electromagnet reacts with the permanent magnet in the speakers. In speakers, where the manufacturer avoids installing a permanent magnet, a second electromagnet take its place. Inside the speaker, the electromagnet is placed in front of the permanent magnet.
The permanent magnet is placed in a compact and fixed position whereas the electromagnet is mobile. As currents of electricity pass through the coil of the electromagnet, the direction of its magnetic field changes rapidly. This means that it is attracted to and repelled from the permanent magnet rapidly in alternate turns, vibrating back and forth.
These vibrations lead to sound produced in speakers. Conventionally the size of the magnet influences the quality of sound. However, with neodymium magnets, we have lighter magnets which are powerful in quality. Also we saw that mostly magnets in speakers are round. Save my name, email, and website in this browser for the next time I comment. All Rights Reserved. How To and Info. David November 10, Save Saved Removed 0. Related Articles. Moving-coil drivers are often considered the most common speaker transducer types.
These moving-coil drivers utilize electromagnetism to transduce energy, thereby making electromagnetic loudspeaker transducers commonplace. Moving-coil drivers are also used in some mobile and computer devices, though these speakers are also often of the piezoelectric-type or are made with MEMS technology.
The main point is that loudspeakers utilize drivers to convert audio into sound. The drivers that utilize electromagnetism and, therefore, magnets are as follows:. The conductive coil is cylindrical in shape and must be suspended within a cylindrical cutaway in the magnetic structure. To achieve maximum efficiency, the magnet must have opposite magnetic poles to the interior and exterior of the coil. This allows for a concentrated magnetic field around the coil.
This is ultimately how the moving-coil dynamic loudspeaker acts as a transducer. The diaphragm movement mimics the waveform of the audio signal and produces sound that represents the electrical audio signal. Since the particular shape of the magnetic structure is practically unobtainable via a single magnet, pole pieces are required. One strong central ring-shaped magnet is used with a few pole pieces to extend its poles to the interior and exterior of the coil.
A cross-sectional diagram is provided below:. So the main magnet in red is shaped like a ring or a thick washer. It has its south pole facing upward and its north pole underneath. A thicker ring-shaped pole piece extends this south pole and provides the boundary just to the outside of the moving coil.
A disc-shaped pole piece is laid underneath the central magnet to extend the north pole. The north pole is furth extended with a cylindrical pole piece the reaches upward and provides the boundary to the inside of the moving coil.
The idea is to get the opposite poles as close to the coil as possible, with the north pole to the interior and the south pole to the exterior.
This causes the greatest number of magnetic flux lines through the coil and, therefore, the greatest amount of coil movement. The moving-coil driver design applies to headphones on a smaller scale and to microphones as well only in reverse.
The magnetostatic planar magnetic loudspeaker driver has been made famous by the brand Magnepan. 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 speaker attached to the speaker creates another magnetic field that opposes the magnetic field created by the electric current going through the coil and changing direction as it goes. These vibrations produce the actual sound we hear from our speakers.
As you can imagine, the larger the magnet or the more current is supplied, the louder the sound from the speaker. For speakers to produce sound, they need to create audible mechanical vibrations in the air.
That means they need something that can vibrate quickly when hit by electric signals. The vibrating item in a magnetic speaker is a diaphragm or cone. The diaphragm is a conical structure made up of a flexible material. When driven by a magnetic force repulsion and attraction — we will explain this more , the diaphragm vibrates.
The magnet allows the speakers to create mechanical vibrations sound by allowing the electric signals to interact with the magnetic field. When the electric signal going through the voice coil changes its direction, it creates a polar movement between the magnet and the speaker.
The magnet helps to create a magnetic field that creates sound vibrations when hit by electric signals. The signals cause fluctuations in the opposing magnetic forces between the magnet and the coil, making it move back and forth through the attached diagram. What matters is that the material can create a magnetic field strong enough tho move they could. You can learn about speaker magnet strength here.
If not, move on to the deeper explanation below.
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