That was a gooood find!

The same way your ears hear more than one frequency.

The sounds around us are composed of a complex range of frequencies mixed together. Those mixed together sounds impact your eardrum causing it to vibrate and you hear it.

If you were able to make your eardrum vibrate the same exact way, and amplify the movement, it would emit the same sound you just heard.

Electronic speakers and microphones are the same.

Very simplified, microphones are just speakers. Electricity applied to a speaker makes it move.

This works in reverse too, moving or vibrating a speaker manually makes tiny bits of electricity that match that movement or vibration.

The complex pattern of sound hitting a (mic / speaker) and the resulting complex pattern of electricity it makes can be recorded.

Then you amplify and play back that pattern of electricity to a much larger and louder mic/speaker and that same sound is reproduced

Your ears or a microphone actually move very very little with sound. So you can hear low and high frequencies at the same time.

Similarly most (not all) headphones are just a single tiny speaker that do a decent job of reproducing most frequencies that humans can hear. They can do this because they don’t have to move very much (and be very loud). Again, like my “your ears in reverse” example.

However large speakers have to move a LOT to make very loud low frequency sound. If a speaker is moving an inch back and forth 500 times a second, ALSO trying to make it vibrate a fraction of a millimeter’s distance, 20,000 times per second at the same time doesn’t sound very good.

So to make loud amplified sound, sound better they divide up the work. Small very tight speakers (tweeters) are good at making high pitched sounds. (But can’t move enough to make loud low frequency sounds)

Large loose speakers (woofers) that can move a lot are very good at making low frequency sounds. (But are not tight enough to make loud high frequency sounds)

Inside a speaker is something called a crossover that divides up the electric pattern such that high frequencies go to the tweeter and low frequencies go to the woofer.

That way you can more accurately reproduce loud sound at much higher volume levels.