Sound level at your seat from the Rotel S14 driving the Dynaudio Contour 20 Black Edition, using the amplifier's rating into this speaker's impedance rather than the headline 8 ohm figure.
Solve for level, or for the power to reach a level.
| Power | Level at your seat | Versus 1 watt |
|---|
Doubling power buys 3 dB, which is barely a noticeable change. Ten times the power buys 10 dB, which is roughly "twice as loud" to the ear. This is why 200 W is not twice as loud as 100 W.
SPL = sensitivity − voltage correction − distance loss + pair bonus + 10·log10(watts)
Sensitivity is nearly always published as dB at 2.83 V / 1 m, not dB per watt. 2.83 V into 8 ohms happens to be exactly 1 watt, so for an 8 ohm speaker the two are the same. Into 4 ohms it is 2 watts — so the same published number is worth 3 dB less per watt. Skip that and you will underestimate what a 4 ohm speaker needs by a factor of two.
This page takes the published sensitivity as printed, which is what every SPL calculator does and what makes the arithmetic checkable: an 88 dB speaker on 1 watt at 1 metre reads 88 dB. Our amplifier matcher deliberately knocks 2 dB off first, because published sensitivity runs optimistic for almost every brand and an amplifier recommendation should have that margin built in. So the matcher asks for roughly 1.6× the power this page does. Both numbers are in the working below; the derated one is the safer figure to buy against.
How fast sound falls off with distance. Outdoors it is 6 dB per doubling — the inverse square law. In a sealed pressure chamber it is 0. A furnished room sits between, and 3 dB per doubling is the honest working figure. It is a control on this page rather than a hidden constant, because it changes the answer by more than any other input.
To skip the arithmetic and get real models, the amplifier matcher runs this same calculation against every speaker and amplifier we cover.