PA-101: A Solid Foundation

November 6, 2011 by TomCat

Here is the first part of a series on Basic PA-101.

This first part I decided to call “A solid Foundation”, and serves as an introduction only.

It is vital that any decisions regarding the purchase of a sound system be made on solid principles and foundations. A sound system is a major investment and the purchase of unsuitable equipment is an expensive and costly mistake.

Getting Going....

So you have been grinding that Axe now for four hours a day and feel you are now ready to hit the big bad world out there with your talent.

Problem: - You have no PA kit and there is no guarantee that the venue you are going to play in has one either.
So you Google....you ask questions etc, only to discover that the world of professional audio appears to be more scary than a Britney Spears Karaoke evening.

So...to start off, let’s get the basic terminology right. Strictly speaking the PA system we refer to here is actually called a Sound Reinforcement System. PA systems as such are usually associated with announcements in public spaces.

So what makes up a basic Sound Reinforcement System?
A typical sound reinforcement system will include the following:
1. Input sources
2. A multi channel mixer
3. Outboard processing equipment
4. Amplification
5. Loudspeakers
6. The cables that connects everything together.
I will endeavour to cover each of the above sections in more detail later, but for now lets look at each of these in brief.

Input sources:
Input sources can be divided into three basic categories as follows:
1. Microphones:
Microphones are by far the most common input devices in any sound system. Microphones are used to pick up the sound of just about any kind of acoustic source there is out there.
Microphones range from vocal microphones optimises for singers, to instrument microphones for all types of instruments.
Microphones also have the lowest electrical output level of all source types so special attention is given to microphone signals to ensure that the best possible audio quality is maintained.
Microphones can also be either connected via a microphone cable or be wireless (more on this in another article)
2. Instruments:
Different instrument has vastly differing signal levels with electric guitars having the lowest levels and keyboards and acoustic guitars with preamps the highest.
3. Line Level Devices:
These include devices such as I-Pods and CD Players.

Multi Channel Mixer
The mixer is probably going to be the most important piece of equipment in your system setup as the quality and features of the mixer will have the biggest influence on the quality, versatility and adaptability of you sound system.
There are many different types of mixers available on the market these days. Many are good, but as with anything, there are also a few bad eggs out there.
The role of the mixer is threefold.
1. Preamplifier to amplify the low level signals of microphones and instruments to a higher level suitable for driving power amplifiers and outboard equipment.
2. Combine or mix different input sources to provide a coherent output to the loudspeakers
3. Route combinations of input sources to different outputs such as the main loudspeakers, stage monitor loudspeakers and outboard equipment.

Outboard Processing Equipment
Outboard Processing Equipment includes items such as effects processors for reverb and delay effects, dynamic processors such as compressors and gates and equalization devices such as parametric and graphic equalizers.
These processors allow us to change the character, tone or dynamics of our input sources to better blend these to provide a more musical result.

Amplification
The mixer itself cannot provide enough power to directly drive the loudspeakers (except when the power amplifier is included as part of the mixer package).
Power amplifiers therefore increase the power of our mixed signals sufficiently to drive the loudspeakers.
The power amplifiers can also be included in the loudspeaker package as well.

Loudspeakers
The role of the loudspeakers is to project the amplified sound from the power amplifiers into the audience.
Loudspeaker for sound reinforcement fall into two main categories, namely Front-of-House (FOH) loudspeakers and stage monitor, or what is also called foldback loudspeakers.

Cabling
Cabling is a vital and often overlooked part of the sound reinforcement system. They are the arteries and veins of your sound system and poor cables will always let you down at the most inappropriate time.

Selecting a Sound Reinforcement System
Now that we have covered some basic introductions regarding the parts of the system, lets look at how one goes about purchasing a system for your needs.

Before you consider anything, there are a few questions that need some answers.
These are:
1.  Are you only a solo artist or is there a band involved? This determines how many inputs and outputs your mixer will need.
2. What are the typical venues you will be playing in? This determines roughly how large and how many loudspeakers you will need to be to fill the venue.
3. What music style do you play? Folk / Acoustic styles will require much less horsepower of your system than Pop / Rock / Metal.
4. How will you transport your system? Is it limited to the boot of your car or is a trailer required?
5. How much money are you prepared to spend?

This introduction does not answer these questions, but the next few articles will, as well as other issues regarding sound systems……..read on…..