Sound Systems: How Do They Work?


Almost everyone has encountered a sound system in their life. Sound systems are everywhere; concerts, weddings, churches, theatres, amusement parks, etc… Sometimes they’re big and sometimes they’re small. But at the end of the day, they all work in the same basic way.

How does a sound system work? Sound systems work by taking an audio input signal, processing and amplifying it through a series of equipment in a specific order and then outputting the signal through one or more loudspeakers.

There are many types of sounds systems – some simple and some very complex. However, they all consist of the same basic components. Read on to find out more!

How Does a Sound System Work?

In this article, I will focus on live sound PA systems – the kind you would see at a concert. This is for a couple reasons –

  1. Because live audio is my job and is what this site is all about!
  2. Because they are typically the most complex type of sound system and it will be the easiest way to understand each component.

But remember, all sound systems in some shape or form use the same basic components, which is what we will talk about here.

Before we get into how they work, let’s take a moment to address the purpose of them.

Essentially, the goal of the sound system is to take a small audio signal and amplify it so that that it can be heard louder and/or by more people.

Sounds simple, right?

Well, the logic is very simple, but the implementation… not as much.

There are many components to every sound system. These include things like a mixing console, crossover, power amps, speakers, etc… Sometimes, many of these things are combined into one piece of gear in order to make it simpler for the end user. However, the more advanced a system becomes, the more these components are separated into individual pieces.

Let’s take a look at each part of the system and get a better understanding of its importance.

Sound Input

It all starts an input. If you don’t have an input at the beginning of your chain, the rest of the system is useless because you will have nothing to amplify.

So, what is the input? Well, it could be anything. There are countless sources of sound you can start with.

It could be a microphone, or a guitar. Maybe a piano or a violin – or even all of them at once! At concerts and theatres, it’s common to use dozens to hundreds of inputs!

Sound Mixer

Your source sound will then travel through some cables and enter a sound mixer – a.k.a mixer/console/desk.

You’ve probably seen a console before, especially if you’ve been to a concert. They are the big table looking things sitting out in the audience with all the buttons, sliders, knobs and lights. We mix engineers often get asked if we know what each knob and button does. And the answer is yes… yes, we do 🙂

The job of the console is to set the signal of the source to a practical level, adjust the tone of the source to a desired sound, and then send it to the next part of the chain.

Some consoles are very basic, only consisting of a few channels for a few sources. Other consoles, however, can have dozens or even hundreds of channels for larger and more advanced needs, such as concerts or theatres.

Monitors

The monitors are controlled either from the mixer mentioned above, or a separate dedicated mixer.

Monitors are used for musicians on stage so that they can hear themselves. Most of the time, each member you see on stage will be hearing something different. The drummer may be hearing a lot of drums and bass, while the guitar player only wants to hear his/her guitar and the lead vocal.

This doesn’t only apply to bands though. Monitors are also used for public speakers. It can be a little weird, or even difficult sometimes, to speak without a monitor.

So as you can see, monitors are essential for anyone performing or speaking from a stage.

System Crossover

After the mixer has done it’s job, it then sends the signal to a system crossover.

A system crossover is a piece of equipment that divides your sound system into sections based upon frequency content.

What does that mean?

Well, have you ever been to a concert and saw all the surrounding speakers? There were probably some higher in the air, or even hanging from the ceiling. There were probably also some larger speakers on the floor in front of or beside the stage.

The ones you typically see in the air are designed to handle higher frequency content; like vocals, guitars, horns, etc…

The speakers you typically see on the ground are designed for low frequency content; like the bass drum, bass guitar, low synthesizers, etc…

The crossover takes the signal from the mixer and divides it into multiple signals based on frequency content. If we have a 2-way sound system, then it will divide the signal into 2 parts; the low part and the high part. If we have a 3-way system, it will take the signal and divide it into 3 parts; the lows, mids, and highs.

The reason for this is so we can allow each speaker to perform optimally based upon the frequency content it was designed to handle.

Power Amplifiers

You may have thought it was time to talk about speakers now, but we’re not quite there yet.

PA speakers require a relatively large amount of power to perform. And our crossover isn’t nearly powerful enough to run even a single speaker, much less an entire sound system.

That is where power amplifiers come into play.

Power amplifiers receive the signal sent from the crossover. Since our crossover divided our signal into multiple parts based upon frequency content, that means we will use different power amps for those parts – a single/set of power amps for the lows, mids, highs, etc… respectively.

The power amp then boosts this these signals 10, 20, or even 40 times the original level in order that they can power and be heard through the speakers.Without power amps, the rest of our system would remain obsolete.

Speakers

Last, we have the speakers. Speakers are the last component in the signal chain of a sound system. It is the part that most people can recognize.

The purpose of the speakers is quite simple. It is to convert the electrical signal passing through the sound system into acoustical energy – what we all know of as sound!

There are many types of speakers designed for different applications too. There are line arrays, conventional speakers, subwoofers, monitors, fill speakers, reference monitors, etc…

In the entire sound system, the speakers are the only component that actually makes sound!

Fun Fact!

How long did it take you to read this article? 10 minutes? 15 minutes?

Well, did you know that everything you just read about the signal flow – from the first word spoken into a microphone, traveling to and out of the mixer, into and out of the crossover, into and out of the power amps, and into and out of the speakers only takes a few milliseconds!

Conclusion

As you can see, the logic of a sound system can seem simple. But in reality, there is a lot that happens between the sound source and the speakers. I hope that I’ve helped you understand the basic concept of it all. And I hope it gives you some cool insight that you can use in your own career or simply gives you a bigger perspective of what often goes on behind the scenes!

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