Have you ever stared at a loudspeaker datasheet, scratching your head while trying to figure out what the actual Sound Pressure Level (SPL) will be at 2 meters with twice the input power? You’re not alone.
For electronics manufacturers, translating loudspeaker specs into real-world performance can be quite a not so easy thing.
At Seltech, we believe in making acoustics more accessible—so in this article, we go through a simple yet powerful formula to recalculate SPL for different distances and power levels.
The formula below allows you to estimate the SPL at any given distance and input power, based on the reference values provided in a loudspeaker’s datasheet.
The first term, Spec. SPL, is the SPL value specified in the datasheet—typically measured at 1 meter with 1 watt of input power.
The second term adjusts for the change in input power (expressed in Watts), using a logarithmic scale, where doubling the power increases SPL by approximately 3 dB.
The third term accounts for the change in distance (expressed in meters), reflecting the inverse square law: as distance doubles, SPL drops by about 6 dB.
With this formula, you can confidently adapt datasheet values to your real-world setup—whether you’re powering up or stepping back.
To demonstrate the efficiency of this formula, let’s consider a loudspeaker such as our Seltech CC36C163DN8.
Figure 1 below shows the main characteristics of this speaker, taken from its specifications. We can see that its nominal power is 2 watts, while its SPL is qualified at 1 W / 0.5 m.
Let’s apply the formula presented above to recalculate the radiated sound pressure level at its nominal power and for a listening distance of 1 meter.
The application of the formula allows us to estimate that the speaker radiates a sound pressure level of 77 dB SPL when operating at its nominal power of 2 watts and for a listening distance of 1 meter.
Partner with Seltech to identify and seamlessly integrate the ideal loudspeaker solution tailored to your specific application!