Choosing and establishing a PA system for a live event may be a daunting task. There can be microphones on stage, a mixing console in front of the house, power amps, and speakers. Everything must be precisely calibrated, or you risk destroying the equipment or, worse, having to cancel the event and refund everyone’s money.
Having said that, choosing the appropriate PA in Melbourne or any other place is a lot easier than it appears, and determining what is suitable for you begins with just a few questions. Continue reading to learn how to pick and set up a PA system, whether you’re in a band seeking to supply your system for concerts, an engineer looking to rent PA systems for events, or a venue manager looking to improve your rig.
Let’s start with the fundamentals. Every PA system is made up of 4 parts:
This can range from a modest DJ setup consisting of two turntables and a microphone to a full-fledged stadium extravaganza consisting of line arrays and time-aligned fill speakers. To choose the best PA for your event, you’ll need to know a few specifics about the performance.
You don’t want to turn up to a local cafe with a semi-truck full of line array speakers, or worse, to an arena performance without one. Need more powerful PA systems to fill the arena with sound, but to decide how strong, these four things must be known.
The signal grows softer as you go away from the speakers. This is unlikely to be an issue in smaller venues, as the level differential from the stage to the back of the room will be hardly apparent. However, when you move into larger locations, the drop in level becomes more noticeable.
Once you know the distance between the loudspeaker and the farthest listener, you can calculate how much signal loss you’ll experience in the rear of the arena.
The SPL drops by 6dB every time you increase your distance from the speakers. For example, if you stand one meter (three feet) away from a speaker producing 110dB SPL, the signal will drop as follows:
As a result, even if the music is loud in the front row, individuals in the rear may easily converse over it. Fill speakers, which are additional speakers deliberately placed to maintain the SPL level consistent across the arena, come into play at this point.
The usual rule of thumb is that the louder the music, the heavier it should be. Folk, jazz, and classical music usually have an SPL range of 80-95dB, but pop, hip-hop, and rock have an SPL range of 95-110dB.
You may choose appropriate speakers for the performance after establishing the desired level (be sure to check local noise regulations!). Make sure you select something with a high enough maximum SPL capacity to satisfy your requirements!
Every speaker has a sensitivity rating, which effectively measures how well a speaker translates watts from power amps into SPL.
Smaller PA speakers have lesser sensitivity, which means they function inefficiently compared to bigger PA speakers. Speaker sensitivity is measured by delivering one watt of electricity to a speaker and measuring the SPL from one meter away.
Professional PA speakers can deliver between 95- and 110-dB SPL/Watt/meter, which means that a single watt of power may create between 95- and 100-dB SPL, depending on the speaker.
Now that you know the technical specifications of your PA speakers, you just have one more inquiry before deciding on the best power amps for the performance.
Transient peaks in live music can be as much as 25 dB above the normal volume, causing power amps to peak and generate distortion. There are two ways to deal with this.
That is far more difficult to say than to do. To increase 3 dB of headroom, you must double the amount of power sent to the speakers. That is, if a 1000-watt amp provides 3 dB of headroom, a 2000-watt amp will provide 6 dB of headroom.
While more is nearly always preferable, in most instances you can get away with as little as 3-6dB of headroom. However, just to be safe, it might be prudent to incorporate a restriction.
Most permanent or large installations employ passive PA systems, which need the use of external power amps for the speakers. This enables you to fine-tune the system and dial in the ideal amount of power for each location. Check the tech specs of your speakers for the following figures to determine the correct power amps for your system:
After you’ve decided on the speakers and power amps for the gig, it’s time to put everything together! Although each PA system is uniquely based on the equipment used, below is a general overview of PA signal flow:
After the PA system is in place, all that remains is to test it, adjust the room, and soundcheck the band before showtime!