What size PA system do I need?

by Andrew Bishop

The question of 'What size PA system do I need' is one we get asked often, and it depends on a number of factors. Loud is not always the best PA sound. Today more than ever, a balanced, well voiced, PA speaker system is critical if you wish to entertain an audience.

Are you using you PA system inside or outside?

Outside you need more power especially for the low frequencies as there are no walls to retain the sound. Even a PA system in a marquee will be fine for mid and top range but often lack the bass.

If you're using your speakers in residential areas, there are also other considerations to thing about that can impact the type of equipment you add to your PA System. For example, where noise limitations apply, you don't necessarily need the high levels of volume, as you can't legally use it, so this can sway what gear you buy. 

What PA system is best for a band and a DJ?

In short it depends on the size of the audience. There are two basic methods of delivering sound to an audience:

Point source - individual or groups of speakers on the stage, pole or on the ground pointing toward the people. This is fast and easy to set up but may not throw the sound a long distance. This is perfect for most venues as the sound is focused on the dance floor allowing tables at the side and at the rear freedom to chat.

Line array - strings of speakers hanging down from rigging or a fixed point on the ceiling. These can take over 24 hours to set up correctly to avoid blank spots but in the case of our dual 8" line array throw sound over 300m from the stage. Line arrays also tend to require larger budgets from both a purchase and installation perspective.

Touring bands and DJ's prefer the portable and quick 'in and out' set up of point source systems. These are fine for audiences up to approximately 3,000 people when the right equipment is used.

Very large auditoriums and events, especially outside, use line array, However, a note of caution, many prefer line array for smaller audiences because of how it looks, but not necessarily how it sounds. 

In all cases the most important factor when it comes to purchasing a PA system is sound quality not sound quantity. Getting the facts and talking to an expert who can help spec out your requirements based on your individual needs is always recommended, as ultimately, this will save you money and deliver a better experience for your audience.

How powerful PA system do I need? 

How many watts do you need for a PA system is another common question we get asked. Many measure power in watts which is not necessarily the best way. This can be very baffling as some quote very high figures which can be misleading to the user. For example, a PA System claiming 2,000w PMPO (Peak Music Power Output) is actually equal to 500w RMS.

At BishopSound, we recommend measuring PA systems using RMS or SPL (sound pressure levels) when calculating PA power output. For reference, An SPL of 120db (decibels) is the equivalent of standing 200 feet away from a jet aircraft taking off.

In a 5,000 seater arena an SPL of 98db means you cannot have a conversation with anyone sat next to you. Read this is article to learn more about SPL - Loud Speakers! How Loud Is Your LoudSpeaker? – BishopSound

Finally, what should be in a PA system?

Here is a checklist for a point source passive PA system

  • A power conditioner to protect you, your equipment, your reputation and life from nasty power spikes on the 240v mains supply
  • The best mixer you can afford
  • A minimum '2 in 4 out' Signal Management Processor or Active Crossover
  • 2 x 2 channel power amplifiers or 1 x 4 channel power amplifier
  • High quality BishopSound speakon to speakon cables to connect amplifiers to the speakers.
  • Top quality BishopSound XLR cables to link to the signal processor and then to the amplifier.
  • Subwoofers for the low frequencies and full range speakers for the mid/tops. Match the RMS ratings of the speakers 10% higher than the RMS ratings on the amplifiers. Take notice of the impedance.
  • Covers to protect your investment when storing or touring

At BishopSound, we have a range of PA Systems configured to help get you started, or alternatively, you can build your own PA System Package using our online bundle builder.

Any questions and for unbiased professional advice on a PA system for a fixed installation or touring is freely available by contacting andrew@bishopsound.com or calling 01765 698233 weekdays.