If you’ve ever seen the inside of a common speaker then you know well and good that they have magnets in them.
An interesting question that I got from one of the producers I’m coaching is:
“Can a speaker work without a magnet?”
This question made me think of writing a complete blog post detailing and explaining the role of magnets in speakers and why they’re such a crucial component of most common speakers.
So without further ado, Can a speaker actually work without a magnet?
Piezoelectric speakers are constructed without them relying on magnets to produce sound this means they can work without magnets. On the other hand, Electro-dynamic speakers are constructed to work with magnets which means they can’t be functional without a magnet because AC signals will not be converted into motion to make the diaphragm vibrate in tune.
Why do speakers have magnets?
It’s common for you to find magnets inside most speakers and the reason for this is because magnets create an opposing magnetic field which result in vibrations in tune which are the sounds we hear.
So let’s take this explanation further….
In order for speakers to work they need an electric current. The role of current in speakers is to create a magnetic field.
A magnetic field is simply a region around and near a magnetic material or a moving electric charge within which the force of magnetism acts.
With that said, current in speakers creates a magnetic field when current goes through a coil.
The speaker that is attached to the speaker creates another magnetic field that in turn opposes the magnetic field created by the electric current going through the coil and changing direction as it goes through.
These opposing magnetic fields are responsible for creating vibrations in the speaker’s cone or panel and this is possible because the cone is attached to the magnet and coils.
These vibrations are what we perceive as sound with our ears.
So… if you put everything into context, you can easily figure out that when we increase the size of the magnet or simply supply and run more current in through coils… We will get louder sound from our speakers.
I’m simpler terms, for speakers to generally produce sound they need to create what we can term as audible mechanical vibrations… if you’ve ever taken a deep dive into understanding sound then you’ve probably come across something referring to sound as simply “vibrations that travel through air”.
So, for speakers to produce sounds they need something that can vibrate quickly enough when hit with electric signals. The vibrating component in speakers is the diaphragm or cone.
The diaphragm has a cone like shape and it is made of flexible material.
When the diaphragm is driven by a magnetic force, it vibrates.
This is why you’ll find the diaphragm attached to a coil that is placed near a magnet.
So it vibrates when an electric current passes through it.
The magnet allows the speakers to create 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 magnets role is 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.
The truth is, the type of magnet doesn’t even matter as speakers use many different types of magnets.
What matters is that the material that can properly create a magnetic field strong enough.
Coils are normally small and lightweight, therefore speaker magnets don’t need to be extremely strong.
Piezoelectric Speakers
To give you a short background in to this, let’s consider piezoelectric material.
Piezoelectric material is simply material that changes its shape when it is exposed to electric fields.
Piezoelectric speakers therefore use electric fields to cause piezoelectric material to change its shape at specific times in order to create sound.
The piezoelectric effect is mostly employed in the construction of thin form factor speakers that can be used in place or in the absence of eletro-dynamic speakers.
Piezoelectric speakers are sometimes called Piezo Speakers or Ceramic Speakers.
They produce sound when a piezoelectric material is exposed to an electric field that causes it to change its size. Piezoelectric materials will either shrink or grow when they exposed to or isolated away from electric charges.
Piezoelectric Vs. Electro-dynamic
Piezoelectric speakers are similar to electrodynamic speakers in that they are able to convert potential difference into motion.
Generally, electrodynamic speakers are made by passing an electrical current through coils of wire in the presence of a magnetic field.
The resulting attractive or repulsive force between the wire and magnet are then used to move a speaker cone or diaphragm that creates the disturbances in the air, hence producing sound.
Piezoelectric speakers can be manufactured to be extremely thin and still have acceptable sound characteristics.
The nature of the wire coil that is used to be able to generate magnetic fields in the electrodynamic speaker means that these speakers should be treated as inductive loads when designing driving circuits.
Piezoelectric speakers are treated more as capacitors when designing driving circuits.
One of the reasons why Piezoelectric speakers have become popular is because they are more environmentally robust than electrodynamic speakers and they can function in direct contact with substances other than air; this property is useful, for example, in underwater applications.
Traditional electrodynamic speakers must be protected from the elements.
Compared to their electrodynamic counterparts, piezo speakers need higher drive voltages, plus they have low impedance at higher frequencies which means that large amounts of drive current is necessary for high frequency audio signals.
Final Thoughts
Piezoelectric Speakers can work without magnets while Electro-dynamic Speakers cannot work without magnets.
