How can a single speaker, such as earphones, produce highs and lows at the same time
In: Technology
[This figure should help explain it.](http://proaudioencyclopedia.com/wp-content/uploads/2015/07/Figure-1-5.png)
A shows 4 waves each with different frequencies and C shows what you get when you combine those waves together. (Ignore B and D). A combination of different sound waves creates a single wave with a unique pattern. So instead of a speaker moving in and out by same amount (wave amplitude) at a steady rate (wave frequency) it does a mixture of varying amplitude and frequency to create one sound wave that sounds like what you get when you combine lots of different sounds.
Copy pasted this from last time I answered a similar question – [https://www.reddit.com/r/explainlikeimfive/comments/c7lm6z/eli5_how_are_we_able_to_hear_multiple_frequencies/](https://www.reddit.com/r/explainlikeimfive/comments/c7lm6z/eli5_how_are_we_able_to_hear_multiple_frequencies/)
A sound wave has a single pressure value at any given point in time, so a single speaker can reproduce almost any sound wave by moving in complex ways. After all, a microphone or eardrum is picking up sound the same way- one pressure level at any given instant. The pressure can change like a sine wave which is a single frequency. Or it can be complex and contain many frequencies. For instance, a [square wave contains many odd harmonics](https://en.wikipedia.org/wiki/Square_wave#/media/File:Spectrum_square_oscillation.jpg) of the fundamental frequency.
Different sizes of speakers are ‘specialized’ for different frequencies. That does not mean that a single speaker can not output a broad band of frequencies.
Every tone, every sound is a combination af various different frequencies, and the sum of those is a weird mess of a signal, and it works the other way round, every messy signak is just the sum of several sine waves with different amplitudes and frequencies (search for Fournier Transform).
Practically any speaker can turn every signal into sound, but depending on size, mass and corpus some frequencies are amplified better (search for resonance), multi speaker designs are therefore capable of better sound quality. To smoothen the loudness of a single speaker electronic low or high passes are set, adjusting those is what you do on an equalizer. If you had no electronics adjusted for the speaker size you would hear the resonant frequencies very loud and others barely.
Because sound isn’t linear and has a spectrum with no bottle neck to limit only one sound being produced at a time.
Soundwaves of different sizes combine, just like waves in water. Small short waves (high frequencies) can exist as parts of bigger long waves (low frequencies).
What your eardrum picks up
is the resulting combined wave pattern of all the sound sources around you. The brain does all the work of breaking the signal back down into individual sounds from different locations.
When you are playing back a recording, what the speaker does is really just repeat the air vibration pattern that the microphone was subjected to.
I love this old educational film and its animations, I think it explains the concept well:
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