What Size PA System Do You Need? A Simple Sizing Guide

50 people in a bar is a completely different job to 500 in a field. The PA system that nails one will either be massive overkill or totally useless for the other. Picking the right size matters because too small means the back of the crowd can't hear, and too big means you've spent money on gear that's sitting at 20% of its capacity.

We put together PAs for events around Christchurch and Canterbury every week, so here's a straightforward guide based on what actually works.

The Basics: What Makes a PA "Bigger"

A PA system is made up of speakers (tops), subwoofers (subs), amplification, and a mixing desk. A small PA might be two powered tops on speaker stands. A large one could be a flown line array with a dozen boxes per side, a wall of subs, and a dedicated front-of-house desk.

The key factor is coverage. You need the sound to reach everyone clearly, at the right volume, without distorting. More people and more space means more speakers and more power.

Up to 50 People, Indoors

For a small indoor event (think a birthday at a bar, a work function in a meeting room, or background music at a cafe), a pair of powered tops on stands is usually all you need. No subs, no mixing desk beyond a small mixer or even just a phone plugged straight in. This covers speeches, playlists, and low-volume background music easily.

If there's a solo acoustic act or a single speaker doing a presentation, this setup handles it fine.

50 to 150 People

Now you're looking at a proper small PA. Two tops on stands plus a sub or two on the ground. The subs fill in the low end, which matters a lot if people are dancing or if you've got a DJ playing. You'll also want a basic mixing desk so you can control levels properly.

This is the sweet spot for 21st birthdays, engagement parties, small corporate events at places like Tūranga or The Atrium, and indoor gigs with a solo act or duo. If there's a band, you'll probably want foldback monitors on stage too, which bumps the setup up slightly.

150 to 300 People

A mid-size PA. More tops (possibly four), more subs (two to four), a proper mixing desk, and likely a dedicated sound engineer to run it. The room matters a lot here. A 200-person event in a low-ceiling venue with carpet is very different to 200 people in a high-ceiling warehouse with concrete floors. Hard surfaces bounce sound around and make things muddy, so you need to plan for that.

This is the range for school balls, medium corporate events, and decent-sized gigs. If it's at somewhere like the Christchurch Town Hall or a large restaurant function room, we'd spec the system based on the actual space, not just the head count.

300 to 500 People

You're into line array territory. Line arrays are columns of speaker boxes that hang (or stack) vertically, and they throw sound much further and more evenly than point-source tops. For a crowd this size, especially if it's a standing event, you need that even coverage so the people at the back aren't straining to hear while the people at the front are getting blasted.

Expect a full front-of-house setup with a proper desk, cabling, and one of our production crew running it. This is where the difference between a good PA and a bad one becomes really obvious to the crowd.

500+ People

Large events, festivals, outdoor concerts. Full line array systems on both sides, sub arrays, delay speakers for the back of the crowd if needed, and a full production team. We've done shows at Hagley Park, North Hagley, and outdoor festival sites across Canterbury at this scale. At this level, the site layout, stage position, and noise restrictions all factor into the system design.

If you're running an event this size, you probably already know you need a proper production company. Have a look at what we carry or just get in touch and we'll come to site.

Outdoor vs Indoor: The Big Difference

Outdoors, there are no walls to help contain and reflect sound. Everything you pump out disappears into the air. Wind makes it worse. As a rule, you need roughly double the power outdoors compared to indoors for the same crowd size. A PA that fills a hall easily for 200 people might only cover 100 comfortably in an open field.

If your event is outside, tell us. It changes the spec significantly.

Not Sure? Just Ask

You don't need to figure this out on your own. Tell us the venue, the crowd size, and what kind of event it is, and we'll recommend the right speaker setup. We'd rather send the right system than have you guess and end up with something that doesn't work.