Amplifier Power Calculator

For a typical 250 seat church with a blended service, about 640 watts per loudspeaker, or roughly 1,900 watts of total amplification across three boxes. But watts alone is the wrong question: the same room needs a sixteenth of that with a highly sensitive horn-loaded cabinet and eight times more with a modern full band. Enter your own throw distance, speaker sensitivity and service style rather than using a watts-per-seat rule.

Headroom is the difference between the average level and the peaks. Music and speech peak roughly 10 to 12 dB above their average level, and every 3 dB doubles the power required, so 12 dB of headroom means sixteen times the power of the average alone. An amplifier sized only for the average clips on every transient, which sounds harsh and is the fastest way to destroy a compression driver.

Yes, and this surprises people. The accepted rule is an amplifier rated 1.6 to 2 times the loudspeaker continuous power. A large amplifier used sensibly delivers clean peaks and stays well within the speaker limits. A small amplifier driven into clipping sends a sustained, nearly square waveform into the speaker, and it is that, not excess power, that kills most tweeters.

It needs more power because the furthest seat is further away, not because there are more people. Distance is the only geometric factor in the calculation, and it follows the inverse square law: doubling it costs 6 dB and quadruples the watts. A wide shallow room with 400 seats can need less power than a narrow deep room with 250.

No, but they answer it for you. A powered loudspeaker has its amplifier matched to its drivers by the manufacturer, so the question becomes whether that cabinet as a whole can produce the level you need at your distance, which is what the maximum SPL specification tells you. The arithmetic here is most directly useful when you are choosing a separate amplifier for passive speakers.

Speech-only services run comfortably at 70 to 78 dBA, a traditional service with hymns and organ at 78 to 85, a blended service at 85 to 90 and contemporary worship at 92 to 98. Design for the loudest programme the room will actually host, then run quieter. Note that anything sustained above 85 dBA carries a real hearing-exposure obligation and that offering ear protection is reasonable above about 95.