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Intro to live sound equipment

Choosing the right gear for your live sound system


Simple PA system diagram

The simplest PA system is a microphone or instrument plugged into a powered speaker

Whether you only need a single microphone and a speaker or a full kit for your band, it pays to understand how a PA (public address) system works. At its simplest, sound goes into microphones, through mic cords to a mixer. It leaves the mixer and goes to an amplifier, which sends it on to speakers. The speakers, in turn, broadcast the sound to the audience.

How powerful does my PA system need to be?

To answer this question, you need to know how you intend to use the PA system. Is it for a school auditorium or a bar? Are you giving talks to small groups or are you a 5-piece rock band? Once you know how you intend to use the system, the gear you need starts to fall into place.

Volume (space) and volume (loudness)

The PA system you want should easily fill the volume of your intended space, and sound loud enough for its intended purpose. The music system in a nice steakhouse, for instance, allows a singer/piano player to entertain the whole restaurant without blasting any diners out of their seats. A small dance club will have some high-powered subwoofers that help keep its customers coming back to the dance floor.

Another factor will be the number of people in attendance. The more people there are in the audience, the more the sound will be absorbed by their bodies, and the more it will become necessary to increase the volume to compensate.

This chart is a very rough estimate of how powerful a system should be, depending on the size of the space or audience. Use these numbers as general approximations — a 100- or even a 200-watt difference in the larger systems won't matter. When in doubt, pick a higher power value — extra headroom usually comes in handy.

Recommended total PA system power for different venues and sound levels Conference room, coffee house, school room;
up to 50 people
Small auditorium, restaurant, bar;
up to 200 people
Auditorium, theater, church, club;
up to 500 people
Talking 50 watts RMS 200 watts RMS 500 watts RMS
Acoustic ensemble with vocalists 100 watts RMS 400 watts RMS 1,000 watts RMS
Jazz band 150 watts RMS 600 watts RMS 1,500 watts RMS
Orchestra and chorus 200 watts RMS 800 watts RMS 2,000 watts RMS
Rock band 225 watts RMS 900 watts RMS 2250 watts RMS
Techno/dance/hip hop 250 watts RMS 1,000 watts RMS 2,500 watts RMS

Building a sound system

Now we'll examine each piece of equipment you might need for a sound system. If you're doing anything more than having a single person speak to a small room, you'll need most of these items.

Speakers

Speakers are the workhorses of your system, and how many you need depends on what you're doing. Read our Live Sound Speakers Buying Guide for more details, but here are the types of speakers you might need:

  • Main speakers – Speakers come in two categories. Active speakers are powered, meaning they have amplifiers built into the speaker cabinets. All you have to do is connect your instrument or mixing board. Passive speakers are unpowered, which means you need to add an external amplifier. There are pros and cons to using each type of speaker, and it greatly depends on how you intend to use your PA system. For example, powered speakers are easier for travelling bands since all the processors and power are built in. Unpowered speakers are more flexible since you can choose how much power and what kind of processing to use in your system.
  • Subwoofers – Subwoofers are used to reinforce the deep bass sounds of kick drums, bass guitars, and synthesizers in order to add impact and excitement to any kind of music, but especially dance music. If you intend your PA for speeches and lectures, folk music, or a chorus, you probably won't need a subwoofer.
  • Monitors – Monitors are speakers set up so musicians can hear themselves over the noise of the crowd and musical echoes from the venue, and thus be able to play better. The "sound guy" can usually benefit from having a monitor or headphones, too.

Amplifiers

If you're running passive speakers with separate amplifiers, each amp should have at least as much or, better yet, more output power than the total wattage ratings of the speakers it's driving. Having extra wattage available (headroom) ensures clean, distortion-free sound, especially during sudden musical peaks. See our Pro Audio Amplifiers Buying Guide for more details and advice.

Mixer

The mixer is the brains and control center of a PA system, and the coolest place to hang out. All of the sources of music and sound can be mixed and then sent out to the amps and speakers. The mixer has volume and tone controls for each input channel, allowing you to balance the individual signals and create a clean output signal. Learn more about mixers and how to choose the right one in our Mixers Buying Guide.

Sound processors and equalizers

Most of the sound processing you need is likely built into the mixer and amp, especially if you're just starting up. Adding more complex processors give you even more control over the sound.

  • Equalizers – Equalization lets you adapt your sound to a room's acoustics or finesse the sound of an instrument at a particular frequency. Some amps come with equalizers built into their input circuitry. Some mixers have them in their output sections. And of course, there are the outboard EQs that give you the greatest amount of control. Where a mixer usually has high, mid, and low tone controls (a 3-band EQ), an outboard equalizer can offer, for instance, 15 or 31 bands of control over the audio spectrum.
  • Limiters – Another common device found in amplifiers and powered speakers, or as an outboard unit, is a limiter. A limiter imposes a set limit to the output level of the amplifier so it will never exceed the capacity of the speaker and damage it. A limiter is like a safety valve on a pressure cooker — you'll never have to worry about it blowing up.
  • Effects – The output sections of many PA mixers feature acoustic effects like reverb and echo, which can be used to color the sound for dramatic and pleasant effects. If your mixer's onboard effects aren't enough for your needs, there are varieties of outboard effects devices you can get that can produce countless numbers of sonic effects.

You'll find much more detail about sound processing and equalizers in our Buying Guide for Signal Processors.

Microphones

For live sound applications, don't buy any microphone so expensive it'd give you a panic attack if it gets dropped or knocked to the ground. Expensive condenser and ribbon mics sound great, but belong back in a safe studio. Dynamic microphones offer more rugged and practical solutions for everyday use. (Condenser, ribbon, and dynamic mics get their names from the different ways they create signal.) Many mics come with their response curves (or "voices") tailored for specific instruments, like vocals or drums.

Learn more about microphones in our Microphones Buying Guide.

Accessories

There are some essential accessories to get, in order for your PA system to function.

Cables

All of these sound components need to be connected somehow. The cables you need depend on the component. You'll find a variety of connector types on the gear and cables available. For a solid rundown, check out our pro audio cable guide.

Mic Stands

Mic stands hold your microphones where you want them. They come in many different configurations and shapes, so you can place and hold a microphone in any position and in any situation. A mic stand can be very short, for holding a mic on a desktop, for instance, or very tall, with an extension or boom arm and counterweight, for holding a mic up high and off to the side.

Speaker stands

If your PA speakers are on the floor, it's pretty obvious that only the front row of people will hear the music properly, and they'll be in the way of everyone else hearing it. A way around this is to elevate each of your speakers with a speaker stand. Most PA speakers have a socket or other kind of holder, so they can be mounted on a stand. Just make sure the stand you pick is rated to hold at least as much as the speaker weighs.

AC power conditioning for gigging bands

As many traveling musicians and PA operators have found out over the years, the electrical AC power systems in many restaurants, bars, and nightclubs can be noisy and unstable enough to cause distortion, noise, and even dangerous electrical shocks. If possible, all of your PA equipment should be plugged into the same 120-volt service line, or AC outlet. This ensures that all grounds are at the same electrical potential at the same time, which prevents shocks and eliminates humming "ground loops."

But even that won't be enough sometimes, and only isolating your PA's power supply from the "house system" will fix a noise problem. A great solution is a power conditioner, a device that filters out noise, protects against surges and transient voltage spikes (like when a freezer or air conditioning unit pops on), and provides multiple outlets of alternating current that are all in phase with each other. Cleaning the AC power like this before your PA uses it almost guarantees shock-free connections and lower amounts of noise.

Tools of the trade that you shouldn't forget

Finally, here are a handful of items that belong in every sound guy's gear bag:

  • Power strips and extension cords — make sure you accommodate every piece of gear that needs to be plugged in.
  • Duct or gaffer's tape — because it's the fastest way to hold down or repair something.
  • Flashlight — you'd be surprised how many times you end up looking for something in the dark.
  • Spare batteries and fuses — because the show must go on.
  • Pocket knife or multi-tool — so you can repair almost anything.
  • Spare mic clips (holds the mic to the stand) — the originals break and often mysteriously disappear.
  • Direct box, or DI (direct input) box — a small device used for sending low-level instrument signals, like those from guitars and bass guitars, to a mixer's mic or line-level input.

Examples of PA systems

Here are a few basic diagrams of what most PA systems will look like. The real differences are in where the amplifier is located: built into the mixer, built into the speakers, or an external component.

Basic PA system diagram

This PA system uses a powered mixer to send power and signal to the speakers

Built-in power — Whether the amplifier is located in the mixer or in the speakers is a matter of choice. Either way makes setup and tear-down of the gear easier when you're on the road. 

Basic PA system diagram

In this system, we're using a regular mixer and powered speakers, a popular arrangement for travelling bands and DJs

External amplification — The greatest flexibility comes when the amplifier is a separate component. This makes it easier to replace any piece of the system, but will require longer to set up. It's best for systems that are being permanently installed somewhere.

PA system diagram

The traditional PA system uses an external amplifier to power passive speakers

Multiple amplifiers — PA systems for larger locations or very loud bands will need multiple amplifiers and quickly become more complex to set up. In systems like this, the most important piece of equipment is the sound guy.

PA system diagram

Larger, more-complex audio systems might route the audio signal through a crossover into multple amplifiers and speakers

Put together the PA system that's right for you

As we mentioned throughout this article, be sure to read our other shopping guides for more detailed info for each component and browse our pro audio equipment offerings. If you have any questions not answered on our site, or don't have the time to research, contact our advisors. They're available via phone, email, or chat, and are always ready to help.

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