What is a public address system, and how do you choose one?

A public address system, usually called a PA system, is a set of equipment that lets one person speak to many people, or lets music play across a whole building. You will find one in most schools, mosques, shops, offices and factories, even if you have never noticed it. The announcement before the school bell, the background music in a supermarket and the speech in a prayer hall are all carried by a PA system.

This guide explains the parts in plain words, the choices that matter, and how to arrive at a system that suits your space. It will also help you prepare for a quote.

What a PA system includes

Every PA system has four parts.

Sources. These are what you want people to hear: a microphone for speech, and a phone, USB drive, SD card, FM radio or computer for music. Many Audible amplifiers have a built-in USB or SD player, so a separate music player is often unnecessary.

An amplifier. The amplifier takes the weak signals from your sources, mixes them and gives them enough power to drive the speakers. A PA amplifier usually has several microphone inputs, volume controls, tone controls and more than one speaker output. Read more about the range on our PA amplifiers page.

Speakers. These turn the signal into sound. In an installed system they are usually mounted in the ceiling or on the wall, so that sound comes from many places at a moderate level instead of from one loud box. See our ceiling speakers and wall speakers.

Cables and microphones. Good cable and a suitable microphone are as important as the amplifier. A cheap microphone placed badly makes any system sound poor.

Zones: the most useful idea in a PA system

A zone is a group of speakers that can be switched and adjusted together. A school might have a zone for each block, a zone for the playground and a zone for the office. With zones you can send an announcement to one classroom, one block or the whole school, and play music in the canteen while the library stays quiet.

When you choose an amplifier, check how many zones it has. The USB-80A and the A-2120H have two zones. The PA-260 and PA-380 have two zone outputs that can be used separately or together. The LPA-150EC has five independent zones.

Two ways to connect speakers

Speakers connect to an amplifier in one of two ways, and the choice shapes the whole system.

Low impedance, such as 8Ω. This is the simple method used in small rooms. One or two speakers connect directly to the amplifier. It is easy and works well when cable runs are short.

High voltage, such as 100V or 70V. In a large building, long cable runs and many speakers make the simple method impractical. A 100V line system uses a transformer on each speaker, so many speakers can share one amplifier over a long cable. It is the standard choice for schools, mosques, factories and shops. Our guide on 100V line speaker systems explains it step by step.

Speech or music?

Think about what the system will do most of the time, because it affects the choice of speakers and placement.

For speech, clarity is everything. Place speakers close to listeners so each one can stay at a low volume, and avoid pointing speakers at hard walls that bounce sound back. For background music, even coverage matters more than power, so a larger number of small speakers works better than a few large ones.

How to choose, step by step

1. List the areas. Write down every room or area that needs sound, with its approximate size.
2. Group them into zones. Which areas need to be controlled together, and which need their own volume?
3. Decide speech, music or both. This tells you how many microphones and sources you need.
4. Count the speakers. Use the size and ceiling height of each area. Our guide to ceiling speaker spacing gives a starting method.
5. Size the amplifier. Add up the power of all speakers on each output and choose an amplifier with spare capacity, usually about 20 to 30 percent.
6. Choose the microphones. A fixed desk or lectern suits a gooseneck microphone, while a presenter who moves is better served by a head-worn microphone. See choosing a conference microphone.
7. Plan for growth. If you may add a classroom or a floor later, a 100V line system and an amplifier with a spare zone make that simple.

Matching the system to your space

Different spaces lean on different features. A mosque values speech clarity and several zones, as set out in our guide to a sound system for a mosque. A school needs zones and microphones for teachers, which you can read about on the schools and institutes page. A shop needs even coverage and announcements, and a factory needs reliable paging across long floors.

Why PA systems are quoted, not priced

People often search for the price of a public address system in Pakistan, and it is a fair question. The honest answer is that it depends on the project. The number of speakers, the power of the amplifier, the cable length and the number of microphones all change the total, so two buildings of similar size can need quite different systems. That is why Light & Sound gives a quote for each project instead of a fixed list price. The more you tell us about your space, the more accurate the quote will be.

What to send when you ask for a quote

• The type of space and its rough size
• The number of rooms or zones
• Ceiling height, if you know it
• Whether you need speech, music or both
• How many microphones you will use
• A rough floor plan, if you have one

With that, we can suggest speakers, an amplifier and microphones that fit your project.

Request a quote