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Setting up a PA (Public Address) System can be a confusing new world to musicians as there are so many new things to learn and so many options that have to do with all of the new things to learn...

Most musicians start playing in bands when they are young and sooner than later they are going to need to start using a PA.. Pretty much as soon as you add a singer, you're going to need a PA . So it would seem that the singer should be the keeper/user of the PA, right? Wrong. Most of the time it ends up being a guitar or bass player (maybe even the drummer) who ends up handling the PA gear and controls the sound , and usually it happens from the stage... so that means there is a lot more going on than it may seem. I'm going to try to help with some basic information and links to get a good base of info started about setting up the PA that will be needed...

Where to start? That is the question...

When you start looking at a sound system (PA), you can start to see all of the aspects that make the sound system work. Even the smallest PA is going to have Microphones, cables, a mixer/amp, more different cables, stands and speakers. So a basic system for reproducing vocals is going to have at the very least 5 components. Now you can see where this gets complicated. As soon as you need a sound system that is capable of reproducing all of the instruments, you’ve got a lot of things that you may need to learn about and worry about. So let’s look at the beginning of the signal chain, the signal source. It can be many things, so let’s just start by looking over the possibilities.

The most common use for a PA or Public Address (sound system) is to reproduce the singers’ vocals to put them on top of the mix, or sound coming from all of the instruments, at the point of most importance, the audience’s ears. The bigger the venue is, the bigger the sound system is going to need to be to cover the space and the more work the PA will be responsible for in creating an even mix throughout the room. This is going to require that all of the instruments find there way into the mixer, here is how they get there in a typical sound system.

Vocals are captured by a microphone, which converts them to a signal that can be sent along the microphone cable and interpreted/converted at the mixer.

Guitar amps/horn sections are also captured by microphones and the signal is transmitted the same way as the vocals to the mixer. Modern ‘Modeling’ preamps can also shape the sound of the guitar so it can be sent ‘direct’ to the mixer (see the Acoustic guitars, Keyboards and Bass Guitars section form more details.)

Drums also get microphones, in some cases a microphone for each drum and cymbal, to get their signals sent to the mixer.

As you can see, a lot of the instruments will be using microphones. There are actually microphones that are designed for each of the instruments that you may be using, and there are some ‘old standard’ microphones that can get you through most any situation.

Acoustic guitars, Keyboards and Bass guitars can use amps that are captured with microphones, or they can go ‘direct’. The signal from an acoustic guitar, a bass amp or keyboard amp is sent (normally from a preamp output) to a Direct Box (also called a ‘D.I.’ which stands for Direct Inject), a device that uses a transformer to isolate the signal and to make it a ‘balanced’ signal which can then travel along a microphone cable and into the mixer. The instrument signal can even be split before the amp by plugging the instrument into the ‘In’ on the Direct Box and taking the ‘Out’ or a parallel jack on the Direct Box to the amplifier on stage. These instruments can also just go into the Direct Box and into the mixer without an amp on stage, if the venue/stage has an adequate monitor system, but that is a whole different article.

So now you’ve figured out how each instrument can find its way into a mixer. Each player may have a preferred method of placing the microphone to best capture ‘their sound’ , but sound guys will also have their way of doing it. In most cases, if there is a sound guy it is best to let him place the microphones/D.I.s unless you have a certain technique that you need to use for a certain effect.

Here are some Links to some video's that are chock-full of information. I found these simply by searching the Internet, I have no affiliation with any of these sites.

Expert Village

Next Level Guitar

Part 2.

Once you have figured out what you need to reinforce with and how you are going to get each instrument/voice into the PA it is time to 'mix' them together. Mixing and mixers exist in all sound systems from video cameras (the kind professionals use will have a Left and a Right input which the audio person mixes in post-production) to full-scale Stadium filling PA's. The size and features on your mixer can vary from extremely simple to extremely well appointed (and possibly very complicated). Here's a look at the basic forms of mixers and some of the features you may see when browsing through the options.

The first kind of mixer most musicians end up with is a powered mixer, often called a 'Box mixer' due to the common shape or 'Mixer head'. The basic design is this: a small mixer with fairly limited routing options with a built in power amplifier. This type of unit can range from 4 inputs with very little power to 8 or 12 channels with multiple power amps inside. A starter PA system that you may find in a music store will have a 4 channel powered mixer with around 100 watts total power, and will usually come as a package with a pair of small speakers this can get you started in very small situations, but for the most part, you will need a lot more power once you get into any kind of band situation. Bigger, more nicely appointed, powered mixers will usually have two power amps that can be set for Left-Right mains use (One amp is used for FOH-Left and the other amp is used for FOH Right) or for Main-Monitor use (one amp would power both speakers up front for Mains and the second amp would power a pair of monitor speakers.) Built in FX such as reverb, delay may also be an option. EQ for the outputs (main and/or monitor) are usually provided with 7-9 band graphic EQs. In most ways, these are a very good representation of the entire FOH station that all PA/s use and only lack a few of the components.. Lets see... mixer, CHeck!... Processing (FX/EQ) Check!... power amplifier, Check!

THat makes up the basics needed for any PA!!

Once you've 'graduated' away from using that trusty old box mixer, you are probably going to be looking into a component-based pro audio system, non-powered mixers hook into power amps that hook into speakers. Lets look at the basic features/options that a passive (non-powered) mixer may have.

Microphone channels (channels with XLR inputs) will have a handful of controls/knobs

Starting with an input gain (often called a 'Trim') knob that allows you to adjust the microphone preamplifier's gain to compensate for the varying output levels of the items that are coming into the mixer.
Next in line is usually a channel EQ that may have a low cut (high-pass) button and Low, Mid and Hi EQ knobs. EQ's can be much more involved and may have 'sweepable' mids, which lets you select the center point for the mid level boost/cut knob.
Next comes AUX output knobs, the auxiliary outs are used for monitors and/or FX options . Pre-fader Aux sends send a signal that is not affected by the channels fader and are most commonly used for monitor duties while Post-fader sends are affected by the channels fader, and are more commonly used for FX sends.
Pan allows you to select the channels justification in the stereo outputs (if you are running your PA in stereo) , or to select a 'group' to send the channels output to.
Mute switches mute the channel (may actually be an 'On-Off' switch or 'Mute' switch), PFL (Pre-Fader-Listen) send the channels input signal to the mixers headphones.
Group/L-R output slection buttons allow you to assign the channels output to the Left and Right main outputs and/or to one or several of the mix groups (if the mixer has groups).
The channel fader is the 'volume' or 'level' of the channels as it will be sent to the L-R mix, Groups and post-fader Auxiliary outputs.

Now multiply that by 8, 16, 24, 32, 40, etc... and the mixer can look pretty intimidating!!

Now let's take a look at the Output or 'Master' area of the mixer.

Each Auxiliary output will have a level control (knob or fader) that sends the output (mix) to the next step in the line (processing, will discuss that at a later date).
If the mixer has groups, each group will have a fader to control the final output level of that signal. Groups can be used to sub-mix a set of channels or to send the selected group of channels to an outside source (breakout rooms/mutli-track recorder, etc).
FX returns may have a level control in the Master section, however many sound engineers prefer to bring the FX returns into an actual channel to give it some more flexible routing options.
Main Left and Right (Maybe Left, Right and Mono) faders control the overall level for the main mix.

Live sound 101:

Part 3.

After the mixer, what is next? The signal processing that you need is going to change depending on the size and use of the sound system for the venue. A small bar setup may not have much in the way of processing outside of what the mixer offers internally. In larger venues you can expect large racks loaded with all sorts of goodies! Effects (FX) units add sound-altering effects from tame to wild, compression/dynamics can help smooth out a wildly varying signal, equalizers (EQ’s) adjust the frequency response on the output of devices/mixes and crossovers divide the final mix into different frequency ranges in larger sound systems.

Let’s start with signal processing in a common bar-band setup.

Many small mixers (and even powered mixers/box mixers) nowadays offer signal processing options on-board. The usual assortments are reverbs, delays, etc… sound effects that are commonly used to enhance a vocal part or instrument. These units normally have limited adjustability to their effects; you can adjust how much of each channel is going to the FX, and maybe one or two parameters to make the effect work better for your situation. Some may have multiple versions of each effect to give you choices within the different effects options. For vocals/acoustic instruments the tasteful addition of some reverb or delay (or a mix of the two) is most common, as blasting a ‘dry’ (vocal as reproduced by the sound system without FX) vocal in the mix is not always the best choice.

Compression may be offered in small amounts on some of the consumer-level mixing boards, again with limited adjustability. Compression is one of the most often misused and misunderstood devices. While it can smooth out peaks and dips in a signals level, it is most often used too intensely. It is my opinion that compression is best left off unless it is fully understood, as it can be a detractor to the sound instead of being any help if being misused.

Equalizers are pretty common on box mixers, and some non-powered mixers offer a small (7-11) band EQ for the final output stage to give you control over the final output frequency response. Once you move up to a larger or component-based system you will most likely be using EQ’s with 31 bands. Each Frequency is represented by a slider, and there is a level indicator of + or – and the amount, in dB of boost or cut. Best practice indicates that reducing unwanted/problem frequencies is a better option to boosting frequencies. When feedback happens , the EQ slider for the frequency that is in a feed-back loop should be lowered until the feedback stops, often a few bands to either side may be lowered by a lesser amount to cover the frequencies right around the problem frequency. Beyond feedback control some basic shaping of the overall output of your rig will be done with your EQ, just be careful when boosting frequencies.

Crossovers (if needed) are usually pretty much the same, with stereo inputs and selectable frequencies and output levels for the Low, Mids, and Highs. Starting off you may only have one set of speakers for the Front of House. In this case you won’t need a crossover in your rig; the speakers have a small non-adjustable crossover inside them to send the correct frequencies to the correct driver/speaker. With today’s powered speaker options, the units themselves have built-in crossovers so that each amp/driver in the box gets only its intended Frequencies/signal. In larger systems a basic two-way setup may be used, with Lows or sub frequencies (Frequencies below 100Hz) going to a separate amp for the subwoofers and the Mids and Highs going to a different amp for the Top speakers. Very few small bar systems go to a three-way system (With separate amps for Lows, Mids and Highs).

In larger systems the processing will remain essentially the same, only in larger and more adjustable/reconfigurable units.

Pubrocker Live sound Info Archive

GAIN STRUCTURE..

The name of the game is 'Clean'.. Sure, 'Loud' is represented as 'Good', but 'Clean ' is so much better, and can even be 'Loud' , which is 'Good'.......... With audio signals, you want to try to keep it clean through all the circuits that the signal will go through, and you want to present a strong enough signal that the next circuit in line can effectively operate its intended function to the signal. One of the most discussed and least understood ways to make sure you are passing a good 'Nominal' signal and keeping that signal clean is the gain structure, the way you set up the system to get the best quality, non distorting signal to the end users, your audiences ears. Here is a basic write-up I did in response to a basic gain structure question on an audio discussion forum:

Setting gain/Gain structure in a PA system

Hit the 'PFL' or 'SOLO' button on the channel (you'll follow this the same way for all the channels.)

Have the input source (singer, instrument, playback device) going at it's performance level, so make sure drummers hitting hard as he will while playing the show, make sure singers aren't just talking into their mics..... and watch the meter, raise or lower the gain knob on the channel so that the input is reaching -0- at peaks... +3 on peaks is OK too, depending on how dynamic the input source is.... but for this example lets stick to -0-....

Now that you've got all of your inputs coming into the board with a nominal signal, set your aux sends (monitors or FX).. start by turning the main aux level to -0- (should be marked some how, though may not say '0').. now set your primary channels to the nominal '-0-' setting on the aux knob on the channel strip.... if you know the rough settings of the monitor mix go ahead and dial them somewhat, but you'll have more time for that later..

turn on the monitor amps, turn the attenuators (those knobs on the front that aren't 'Volume' knobs in the traditional sense and that {despite much discussion} DO NOT need to be set all the way up) up so that the primary channels needed in those monitors are just a little too loud for the performers...

now go turn the main aux level down to suit the performers, now you've got some headroom should they ask for a little more volume than they initially thought they needed...

Now for the mains... you can dial in a mix if you have performers there, or set up a CD player, set the input to -0- at peaks and set your channel fader to -0- or nominal then set your master output faders on the mixer to -0- or nominal...

Go turn on the power amps for the mains, adjust the attenuators so that the overall volume is a bit too loud...

Now you should have some headroom so if you need things just a hair louder than you normally have them, you are ready for it.. ...

this is just a start, and your use of the rig is going to determine how much headroom you should give yourself (for example, installations may set up with a little less overall headroom because they are typically going to go for the same levels most of the time...... A festival-style live gig outdoors may set the rig up with a lot of headroom to account for the changing conditions of the venue, and the differing acts or performers they may have...

the name of the game is headroom, you should be able to turn your rig up more than you like it without sending any of your signals out too hot, or without risking having your amps clip which may damage speakers...

make sure your amps have clip limiters and use them , set appropriate low-cuts so (even if you have dedicated x-over-amps and subs) you aren't wasting power trying to recreate frequencies that are not going to be reproduced by you system very efficiently anyway....

and make sure you aren't just cranking everything..... it is not always necessary...

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