I'm Jake O'Neal, creator of Animagraffs. And this is how speakers make sound.
The basic speaker design has a motor that drives the speaker back and forth,
attached to a cone to translate this movement into pressure waves that travel through the air.
Let's look at each part in depth: The motor
A voice coil and magnet work together to form the speaker motor.
The voice coil has a long section of thin copper wire wound many times around a
heat-resistant cylinder called the former. When electricity flows through the copper
windings, it naturally generates a surrounding magnetic field.
This phenomenon is what makes an electromagnet. An electromagnet can act just like a permanent
magnet. And yet, incredibly, its polarity or positive and negative pole orientation,
and magnetic intensity, can be changed by altering the supplied electric current.
It can instantly be made stronger or weaker, reversed, or turned off completely.
A large, permanent or natural magnet surrounds the voice coil. This magnet has a top plate, and a
backing plate with a pole piece through the center to focus the magnet's field through the gap.
An intricate electrical signal flows through the voice coil windings, causing it to move
back and forth as its magnetic field pushes and pulls against that of the permanent magnet.
This electrical current is a precise replica of the audio that was originally recorded.
In fact, the entire sound is contained in this impossibly detailed signal.
The cone and suspension The cone translates voice coil movements into
waves that travel through the air. It has its own flexible suspension system made up
of the surround on the outside, and the corrugated spider at its center.
The dust cap keeps debris and unwanted material out of sensitive internal areas.
Underneath the dust cap, the voice coil's copper leads attach to more flexible wires
called tinsel leads that can smoothly deform with intense speaker movement.
Recreating the whole symphony If a speaker only moves back and
forth, how does it reproduce an entire symphony of sounds at the same time?
Let's look at basic sound wave operation
Air is an elastic medium,
meaning that it returns to its original shape once an acting force is removed.
Speakers push and pull air molecules, making them ram into each other in a domino effect.
This wave reaches and moves your eardrum, which sends a signal that your brain
interprets as sound. You could even say that hearing is just movement detection.
While it's often easier on paper to draw waves as a bouncy line,
in reality, sound waves are three-dimensional areas of high and low pressure.
When we turn up the volume, the speaker pushes harder,
sending more forceful waves through the air. The soundwave's pushing force is its amplitude.
To make high and low sounds the speaker vibrates faster or slower. The wave rate
is its frequency, measured in Hertz. Or in musical terms, its note pitch.
From waves to music
A musical instrument produces a unique waveform when played.
Just one note has low, mid, and high range vibrations combined into a complex soundwave.
The most apparent frequency of a vibrating guitar string may be a G note.
And yet, many smaller twitches and movements
travel through the string at the same time, producing tones that your ear also detects.
Here's the exact same guitar string pluck sound,
but I've isolated distinct frequencies from low to high.
A single instrument note is really a sandwich of frequencies where one main frequency stands out.
This "frequency sandwich" is known as an instrument's timbre, or unique
sound. It's making a G note, yes, but it still definitely sounds like a guitar and not a piano.
When two or more instruments are played together, their unique soundwaves
combine into one even more complex, unified wave. Matching frequencies from each instrument merge,
becoming louder but indecipherable from the other. However, many unique frequencies from
each instrument's distinct timbre remain intact and undisturbed.
With a little effort, our ears can still pick out these individual instruments from the mix.
The human ear can discern sound vibrations between about 20 Hz
and 20,000 Hz. That’s a lot of available frequency to work with!
High frequencies ride on the back of rumbling bass waves,
to reproduce an entire orchestra in one impossibly complex, unified waveform.
It's entirely possible for one speaker to handle the whole sound, like earphones,
for example. However, in larger spaces where sound waves need to travel further, some audio setups
divide specific frequency ranges between specially designed speakers. A speaker intended for low,
slow frequencies has a much different design than speakers made for high and fast frequencies.