Outdoor Speaker Coverage Area Calculator

Halfway into your summer dinner and suddenley someone has to yell for more bread because it’s too loud out there? You’re not alone. That’s one reason outdoor audio sucks.

To most folks, the answer lie in purchasing ever-louder speakers. However, as they say: Volume isn’t everything. More often than not, it’s geometry. It is also about the ambient noise floor and how you wired the system so the amp doesn’t fry by the time dinner rolls around.

How to Plan Outdoor Sound

Instead, this page’s calculator turns your patio into a sound design exercise that eliminates guessing.

First: Define listener area, that is, the area in which sound makes any difference at all. It is not the entire property line or the vacant corner behind the grill. The listening area are the seats. Measure a big ol’ rectangle if the set is small and you’ll end up with a recipe that calls for more speaker than necessary. And that just creates a muddy, overlapping mess of audio. Think about chairs, not the pavement.

Then it ask you about the mount height and speaker profile. Mounting height alter the shape of the dispersion footprint, or the area the sound covers. Mounting a speaker high on a wall with a little down angle shoots out a fan shape that spreads wider at ear level than if you hung something low and pointed it straight out.

Next, it will calculate estimated power needed to reach your desired sound pressure level based off standard sensitivity ratings. Then, it subtracts the natural drop in volume caused by sound traveling across the room. This is where most people mess up: they figure out how many decibels their speakers can do and don’t account for how far away from those speaker you are. Distance reduce all that energy before it reaches your ear.

Outdoor installs is also subject to ambient noise, which is a huge factor. A quiet balcony might only need sixty-two decibels at the listener position to be pleasant. Seventy-five or more could work outdoors by a pool with water pumps running, wind blowing, and nearby traffic. To make sure speech is still clear, the tool includes an allowance of ambient noise added on top of the ambient level. This lets you specify how much quieter your installation needs to be different than a party (for example) versus a conversation. For louder situations, you’ll need more infrastructure, including higher wattages and multiple speaker, then for a quieter situation. The calculator takes this into account and makes you face up to it: making a noisy place livable will take way more infrastructure than making a quiet one livable.

The math becomes practical with wiring. On paper, you might have all your speaker coverage just dandy, but on the other hand, hooking up eight speakers in parallel from one amp channel is asking for trouble: you’ll either burn out the output stage of the amp or you’ll blow a fuse. It’s at this point that the tool comes into play and groups speakers into workable loads, typically four or eight ohms per channel. That’s an important safety check. The tool’s page has some reference tables that illustrate what happens when you wire things differently. Two speakers wired in parallel reduce the load to four ohms, no problem for most moddern amps. Wire three in parallel and they reduces it to two point seven ohms, a dicey situation for many typical receivers. You should of used the calculator flags those concerns so that you can modify your wiring plan before purchasing any cables.

The last tweak for smoothness is overlap spacing. If you place speakers edge to edge, there’s a dead zone in the center with less coverage. To solve this, use the calculator and adjust your percentage of overlap. This decreases the speaker-to-speaker distance while increasing the number of units. It’s a matter of balance between consistency and cost. More hardware create a more seamless wall of sound. And it’s a little thing; but it makes all the difference between a patchy-feeling system and one that sounds like a pro did it.

In the end, it’s all about balance outside. It’s balancing noise, volume, area and electrical load. The tool gives you the starting point numbers. Your ears give you the finishing touch. Do the math first and calibrate for actual acoustics of your space.

Next time you shout for bread, you’ll have a clear idea of what happened.