What is speaker sensitivity?

Sensitivity is the SPL a speaker produces at 1 meter when driven by 1 watt of pink noise or a 2.83 V sine wave. A typical passive speaker is 86–92 dB/W/m; a professional line-array box may exceed 100 dB/W/m. Higher sensitivity means louder output for the same amplifier power.

What is the inverse square law?

In a free field, each time you double the distance from a point source the SPL drops by 6 dB. Mathematically: SPL_loss = 20 × log₁₀(d2 / d1). Real rooms add reflections that reduce this loss, so the inverse square law is a conservative (worst-case) estimate.

Why does doubling power only add 3 dB?

Decibels are logarithmic. 10 × log₁₀(2) ≈ 3.01 dB. To gain 10 dB — perceived as roughly twice as loud — you need 10× the amplifier power. This is why speaker sensitivity matters far more than raw wattage.

Is the result accurate in a real room?

The formula gives free-field SPL (outdoors or anechoic chamber). In a reflective room the actual SPL will be higher (typically 3–6 dB) because reflected energy adds to the direct sound. For critical room acoustics use dedicated acoustic modeling software.

What is a typical target SPL for live sound?

Speech intelligibility generally requires 70–80 dB SPL at the listener. Music reinforcement typically targets 95–105 dB for rock concerts and 85–95 dB for corporate events. Reference monitoring in a studio is calibrated to 85 dB SPL per channel.

Can I use this for line arrays or subwoofers?

The formula applies to a single speaker acting as a point source. Line arrays have a different distance-rolloff behavior (cylindrical wave, –3 dB per doubling of distance in the near field rather than –6 dB). For subwoofers in rooms the formula is still a reasonable starting estimate.

Speaker SPL Calculator

Name: Speaker SPL Calculator
Availability: InStock
Author: Nham Vu

Enter speaker sensitivity, input power, and listening distance to instantly calculate the sound pressure level in dB SPL.

Speaker Parameters

Speaker Sensitivity dB @ 1 W / 1 m

dB/W/m

Typical passive speaker: 86–92 dB. Pro line array: 98–106 dB.

Amplifier Power watts

Continuous (RMS) program power delivered to the speaker.

Listening Distance meters

Distance from the speaker to the measurement or listening point.

Quick Presets

SPL at Distance

— dB SPL

Sensitivity

—

dB @ 1 W / 1 m

Power Gain

—

dB added

Distance Loss

—

dB subtracted

Calculation Breakdown

Enter values above and click Calculate.

SPL at Multiple Distances

How the SPL changes as distance from the speaker doubles.

Calculate to see the distance table.

Doubling Distance = −6 dB

Every time you double the distance from a speaker, you lose 6 dB of SPL (inverse square law). Moving from 2 m to 4 m, or from 10 m to 20 m, always costs exactly 6 dB in a free field.

10× Power = +10 dB

Doubling amplifier power adds only 3 dB. To gain 10 dB — perceived as roughly twice as loud — you need 10 times the power. Sensitivity is the most cost-effective lever for achieving higher SPL.

Summary

Enter speaker sensitivity, input power, and listening distance to instantly calculate the sound pressure level in dB SPL.

How it works

Enter the speaker sensitivity in dB (typically found on the spec sheet, e.g. 90 dB @ 1 W / 1 m).
Enter the amplifier input power in watts.
Enter the listening distance from the speaker in meters.
The calculator adds 10 × log₁₀(Power) to the sensitivity for power gain.
It then subtracts 20 × log₁₀(Distance) using the inverse square law.
The result is the estimated SPL in dB at the given position.

Use cases

Estimate how loud a PA speaker will be at the back of a venue.
Verify that a home theater speaker will reach reference level (85 dB) at the listening seat.
Compare two speakers with different sensitivity ratings to decide which needs less amplifier power.
Calculate how many dB are lost when doubling the distance from a speaker.
Check whether a speaker array will meet local noise ordinance limits at the property boundary.
Determine the minimum amplifier power needed to achieve a target SPL at a fixed distance.
Plan speaker placement in a live sound rig based on required coverage distance.
Teach the inverse square law and sensitivity concepts in an audio engineering course.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu