Free tool
Ceiling speaker spacing calculator
Work out ceiling speaker spacing from the room, not from habit. Enter the ceiling height, the speaker's rated coverage angle, and the room size to get spacing, how many speakers you need, and the power each one draws for your target level. Free, and nothing leaves your browser.
Spacing
2.26 m
Speakers needed
24
6 x 4 grid
Power per speaker
0.1 W
Throw to ear
1.6 m
Coverage radius at ear
1.6 m
The usual choice for speech and paging. Circles overlap enough that level stays even as you walk.
Geometry only, on the manufacturer's rated coverage angle at the stated frequency, usually 2 kHz. Coverage narrows at higher frequencies, and the power figure ignores room gain and headroom. Add 6 to 10 dB of amplifier headroom for programme peaks.
Speaker spacing is geometry, not guesswork
A ceiling speaker throws a cone. Where that cone meets ear height it draws a circle, and the size of that circle is fixed by two numbers: how far the speaker is above the listener, and the angle the manufacturer rates it at. Everything else, spacing, count, and power, follows from those two.
The method
- Throw = ceiling height minus ear height, 1.2 m seated or 1.7 m standing.
- Radius at ear = throw multiplied by the tangent of half the coverage angle.
- Spacing = radius times 2 for background music, times 1.41 for speech, times 1 for the most even coverage.
- Power = target SPL minus sensitivity, plus 20 log of the throw distance, then add headroom.
Low ceilings are the case that catches people out. Drop the ceiling from 3.5 m to 2.6 m and the throw nearly halves, which halves the radius and roughly quadruples the number of speakers you need. That is a budget problem worth finding at design time rather than on site.
Designing a real system? Avitly draws the coverage heatmap live on your calibrated floor plan as you place speakers, so you see dead spots before the install and the speakers you place become the lines on your quote.
Common questions
How far apart should ceiling speakers be?
It depends on the throw to ear height and the speaker's coverage angle, not on a fixed number. Work out the throw (ceiling height minus 1.2 m seated or 1.7 m standing), multiply by the tangent of half the coverage angle to get the radius, then space them at twice that radius for background music, 1.41 times for speech, or one radius for the most even coverage. A 2.8 m ceiling with 90 degree speakers gives 1.6 m of radius, so roughly 2.3 m spacing for speech.
What is the difference between edge to edge, minimum overlap, and centre to centre?
They are three densities of the same grid. Edge to edge places the coverage circles just touching, which leaves quieter gaps between them and suits background music. Minimum overlap spaces them at radius times the square root of two, so the circles cross and level stays even as you walk, which is the usual choice for speech and paging. Centre to centre puts each speaker on its neighbour's centre, doubling the count for the flattest coverage, used for music and critical intelligibility.
What SPL should I design for?
Typical targets are 70 to 75 dB for background music in a restaurant or retail space, 75 to 80 dB for speech reinforcement and paging, and 85 dB or more for foreground music. Design to sit about 25 dB above the room's ambient noise floor for speech to be intelligible, and always leave 6 to 10 dB of amplifier headroom on top so programme peaks are not clipped.
Does the coverage angle stay the same at all frequencies?
No, and this is the biggest limitation of any geometric method. Manufacturers usually publish the angle at 2 kHz, but coverage narrows as frequency rises, so a speaker rated at 90 degrees might be closer to 60 degrees at 8 kHz. That is why a layout that measures fine on paper can still sound dull off-axis. For critical rooms, model it properly rather than relying on a single angle.
How do I calculate watts per speaker?
Start from the speaker's sensitivity, the SPL it makes with 1 watt at 1 metre. Add the loss over the throw distance, which is 20 times the base-10 logarithm of the distance in metres, then compare against your target SPL. An 88 dB speaker at 1.6 m throw needs about 0.13 W for 75 dB. Then add 6 to 10 dB of headroom, which multiplies the power by four to ten times, before choosing an amplifier or tap setting.
Does this account for room acoustics?
No. This is direct-field geometry only. A reverberant room with hard surfaces adds reflected energy, so real measured SPL is often higher than calculated while intelligibility is worse. A heavily treated or absorptive room behaves closer to the calculation. Use this to size and space the system, then verify on site with a meter.
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