For live sound amplification, simple studio recording, or merely a quick musical practice session at home, a public address system is a necessity. The standard public address system – known to many, particularly those in the UK, as a ‘PA’ system – has been in use for over half a century, with both an extensive range of venues and public organizations using the systems to spread their message.
The standard public address system is made up of three parts: an input, typically a microphone or an amplified speaker that’s linked to the system; a mixer unit, which allows sound engineers to arrange, control, and mix sound as they see fit, and a set of speakers, which can be placed around an arena or hall to allow the signal from the input source to travel as far as possible without audio interruption.
This is a simple public address system arrangement – one that reflects the type of system seen in an audio recording studio or a small venue. Larger public address systems may draw their signal using a variety of input sources, such as microphones and instrument amplifiers. Although their scale is a great deal larger than most PA systems, the type of technology involved tends to remain unchanged.
So what separates a public address system from a standard home stereo? There are three key factors that distance the two, despite their obvious functional similarities. The first is the nature of use for a public address system and a home stereo. While one is used for high-fidelity home audio, the other’s used for playing back a direct signal – often one that’s unprocessed and completely unoptimized.
This means that the type of sound being produced by a public address system is much more raw and unprocessed than the signal produced by a home audio system. It also means that the public address system, which generally lacks its own distinct ‘sound,’ is able to produce a more natural sound for a public event, concert that may be recorded and mastered later, or any other live sound situation.
The second difference is the type of amplification that’s used. In a standard home audio system, one small amplifier is used to power all of the stereo speakers. The result of this is constant signal to all speakers – an electronic signal that’s even, uninterrupted, and equal all around. The downside of this is that the level of amplification provided is equal, even if the different speakers’ output isn’t.
In a public address system, the opposite is true. A standard public address amplifier – or even a PA mixer – produces no amplification of its own, instead acting solely as a preamplifier. Each speaker has its own amplifier built into it, allowing it to produce the perfect level of sound and clarity for its size and power output. This results in a more variable sound – one that’s tied to each speaker itself.
The final difference is in the intended use of a public address system. While home audio systems tend to have a single use – playing back audio or video – a public address system can be used for any one of hundreds of public audio tasks. Many buildings use the same PA system for live bands and their standard employee pages, due to the versatility and wide usage range of many systems.
The most common public address system tasks include paging employees throughout an office or retail complex, a task that’s easily achieved with a basic PA system; replaying audio in a stadium, arena, or other large outdoor area, or even messaging people in the event of an emergency. Many public address systems are also used for presentations in public areas, and even major keynotes.
Public address systems are also used in public transport, often to remind passengers of their safety and to mark different destinations; and even in small bars and clubs as amplification for live bands or mixed audio. The amount of situations in which a public address system can produce benefits is extensive and impressive – a testament to the device’s utility and incredibly versatile nature.
While there’s no one manufacturer to look at for public address systems, a large range of pro audio companies are involved in the design and creation of such systems. PA systems can be purchased in a number of different price ranges and budget levels, with pricing generally scaling upwards as the system itself grows larger – small systems are inexpensive, while larger ones much more costly.
Most people may never require their own public address system, and that’s fine, particularly once their professional focus is considered. However, for artists that need solid amplification, recording experts that need a powerful audio system, and concert hall owners alike, a public address system can be a versatile, powerful, and immensely valuable audio utility.