Selection calculator
PA zoning & loudspeaker calculator
Estimate the loudspeaker count, spacing, connected tap load and amplifier size for a zoned public-address system. The result is a starting point for the design, not a substitute for a site survey.
Result
Calculated—
Loudspeakers
— m
Grid spacing
— W
Connected tap load
— W
Amplifier + headroom
— A
100V line current
— dB
Estimated level
Target: 75 dB SPL · — per zone on average
How it is calculated
- Coverage radius = (ceiling height − listening height) × tan(coverage angle ÷ 2).
- Grid spacing ≈ 1.732 × coverage radius (hexagonal layout).
- Loudspeaker count = area ÷ spacing², plus 5% for edge conditions.
- Tap load = count × tap power. Amplifier = tap load × (1 + headroom).
- Line current = amplifier power ÷ 100 V. Level = sensitivity + 10·log₁₀(tap) − 20·log₁₀(distance).
The level estimate is a free-field approximation. Room gain, directivity, transformer loss and the actual programme material change the result. The final design uses manufacturer data and a site survey.
One brief, one combined proposal
Want the calculation reviewed?
Send the result with the building data. We will check the spacing against the fire strategy, the corridor rule and the amplifier protection.
Reply within 48 hours · drawings welcome · no obligation