Outdoor speaker calculator
Check whether a speaker and amp will be loud enough where you sit, and which cable size your run needs. Free, no sign-up.
1. Will it be loud enough?
2. Which speaker cable size?
How many speakers do you need?
One stereo pair covers a typical patio or garden seating area. Space the two speakers about 3 to 4 metres apart, 2.5 to 3 metres up, angled down towards the seats.
Add a second pair when people sit more than about 10 to 12 metres away, or when you have two separate areas such as a patio and a lawn or a pool. Two pairs at moderate volume sound better, and disturb neighbours less, than one pair turned right up. You'll need a speaker selector or a second amp to run them.
How the calculator works
Loudness at your seat = speaker sensitivity + 10 × log₁₀(amp power) − 20 × log₁₀(distance) + 3 dB for two speakers. Amp power is capped at the speaker's rated maximum. "Background" means peaks of about 80 dB, "Lively" about 90 dB and "Party" about 98 dB. Music averages around 10 dB below its peaks.
Cable loss is worked out from the resistance of copper cable over the round trip (to the speaker and back), compared with the speaker's impedance. We recommend the smallest standard size that keeps the loss under 0.5 dB, which is very hard to hear.
Results are estimates for open gardens. Walls, fences and the house reflect some sound, so a real garden is often 1 to 3 dB louder.
FAQ
How many outdoor speakers do I need?
One stereo pair covers a typical patio or garden seating area. If people sit more than about 10 to 12 metres from the speakers, or you have two separate areas such as a patio and a lawn, add a second pair near the second area rather than turning one pair up louder.
How far apart should outdoor speakers be?
About 3 to 4 metres apart for a stereo pair, mounted 2.5 to 3 metres high and angled down towards where people sit.
How many watts do I need for outdoor speakers?
It depends on the speaker's sensitivity and how far away you sit. With 90 dB speakers and a 50-watt-per-channel amp, a pair reaches about 92 dB peaks at 8 metres, which is enough for lively music. Use the calculator above for your own setup.
What size speaker wire do I need for outdoor speakers?
For 8-ohm speakers, 1.5 mm² (16 AWG) works up to about 20 metres, 2.5 mm² (14 AWG) up to about 34 metres and 4 mm² (12 AWG) up to about 55 metres, keeping the loss under 0.5 dB.
How does the loudness calculator work?
It uses the speaker's published sensitivity, the amplifier power (capped at what the speaker can handle) and the inverse square law: sound drops 6 dB each time the distance doubles. Two speakers playing together add 3 dB. Walls and fences reflect some sound, so a real garden can be a little louder than the result.