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on video How Speakers Make Sound

 




How do speakers work?
Let's begin with the fundamental question: how do speakers work?

If you read our previous article on how microphones capture sound, you might feel some deja vu, because both microphones and speakers work by using something called a transducer. Simply put, a transducer is an electronic mechanism that takes in one type of energy and puts out a different type of energy.

While the electroacoustic transducer in a microphone measures incoming sound waves from the air and converts them into electrical signals, the transducer in a loudspeaker (also called the driver) takes those electrical signals and throws them right back into the air as bits of high and low pressure.

That's right—a loudspeaker is essentially a microphone in reverse!
To get sound out of a speaker's driver, you first need to connect it to a source of electrical signals (like an amplifier, computer, or musical instrument) using the appropriate set of audio cables.

The speaker can now receive these signals and pass them through a wire-wrapped cylinder called a voice coil, which moves freely back and forth between the two poles of a larger surrounding magnet. Attached to the voice coil is the circular cone, which has an airtight suspension system on either side to keep it under control.

The resulting “push and pull” movement of the cone creates changes in air pressure that move outward from the speaker, which we interpret as sound. Most speakers are enclosed within a cabinet, which helps keep the focus on just the sound waves coming out of the front of the speaker.

The history of loudspeakers
The first speakers can actually be found in early telephone designs from Johan Philipp Reis in 1861. In subsequent decades, they were expanded upon by the likes of Alexander Graham Bell, Ernst Siemens, and Thomas Edison.

However, it took until the early 20th century for the now-ubiquitous moving coil system to really become established. First invented by Oliver Lodge in 1898, the design was successfully patented in 1925 by Edward W. Kellogg and Chester W. Rice, forming the basic principle for almost all speakers in use today.

Things started to really take off in the 1930s as manufacturers sought to improve aspects like overall power and frequency response in the context of movie theaters and large PA systems. Other advancements in the 20th century included systems with multiple drivers for different frequency ranges, design standardization, and better materials for components like the driver cone, magnet, and enclosure.

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