Public Address System
As the name says it is used for “Public-Address” or a way to communicate to a group.
It is best to have a Public Address system in every building as it usually works hand in hand with the fire alarm panel. It is armed with fire alarm message to help warn people around if there is any fire break up and also ease the fire warden to give direction for everyone to evacuate.
Other
Public Address System is also used by Shopping center when they spotted any lost child or use to look for people if there is a need. But walkie-talkie will still be preferred if is just looking for one people.
There is a smaller version of the Public address system where you will see it in use in super-mart when you attend any events.
Designing of Public Address System:
How we go about designing a Public Address system? There is a theory behind which we will need to study before we can come out with a good design.
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How you want to group your speaker together. Please put into consideration the impedance and power needed for each zone. As more speaker is put, the impedance will drop and higher power will be needed. I came out with the table below for a 100v line
Speaker
How do you choose the right speaker? There is a Sound Pressure Level (dB) you have to meet according to the standard of your country so for mine, it will be SS546. So how do we go about meeting the Sound Pressure Level?
-First, you will have to check the Sound Pressure Level (dB/w) on the specification sheet.
-Next, you have to plan where the speaker is mount and measure the distance from the speaker to where your customer will be.
(For every double of distance away from the speaker, the dB will drop by 6 and for every doubling of power from the amplifier, the dB will increase by 3. But please check the power that the speaker can use, it will be shown on the specification sheet. This will help you choose the most relevant and cost-saving speaker for your design)
With this, you will be able to calculate what is the Sound Pressure Level to expect. To double check, you can always use an impedance meter. Some meter comes with the measurement for Sound Pressure Level you can always use that if not you will have to set your meter to measure in dbC.
A good Public Address system will come with line supervision which will frequent keep the impedance in check. It will cut any power to the line if any fault is detected for example the impedance becomes 0 this indicates that there is a short circuit somewhere. To prevent any equipment from getting burnt the line supervision will cut off all power sent to this line until the fault is solved.
Learn about how you come with the number of speaker per zone from here
or learn how you can make changes in Sound Pressure Level here
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Originally published at audiovisualaoce.com on August 6, 2018.
