Speaker Sensitivity Tester

Speaker sensitivity (sometimes loosely called efficiency) is how loud a speaker plays for a given input, quoted as dB SPL measured at 1 metre with 1 watt of input — written “dB/W/m” or “dB @ 1W/1m”. A higher number means more loudness for the same power: a 90 dB/W/m speaker is 3 dB louder than an 87 dB/W/m one driven identically, which is the same as doubling the amplifier power. Sensitivity is set by the driver and cabinet design and is independent of the volume knob; it tells you how much amplifier you need. Note that sensitivity and efficiency are related but not identical: sensitivity is measured at a fixed voltage (2.83 V, which equals 1 W into 8 Ω), while true efficiency is the percentage of input electrical power converted to acoustic power — typically 0.1–3 % for a conventional moving-coil driver. A 4 Ω speaker driven with 2.83 V actually receives 2 W, so its sensitivity figure looks 3 dB higher than an otherwise identical 8 Ω model — always check which impedance a spec is referenced to.

Measuring the absolute figure properly requires a calibrated measurement microphone and SPL meter in a controlled space, a known 1-watt drive level (2.83 V into a nominal 8 Ω load), and the mic exactly 1 m on axis. A phone or laptop mic is not calibrated: it has its own frequency response, unknown gain, and usually automatic gain control that fights you. So this tool does not try to report an absolute sensitivity number. Instead, the mic mode does something a phone mic can do honestly: a sensitivity comparison between two speakers. With the amplifier set once and never touched, you run a speaker A/B test: play the same signal through speaker A and capture the average level the mic sees, then through speaker B in the same spot, and the tool reports the difference in dB. Because both speakers share the same (unknown) mic gain and room, that difference is a meaningful relative level difference even though neither absolute reading is calibrated. If you want to check how two speakers compare across the audio spectrum rather than just an averaged level, the speaker frequency response test sweeps the full bandwidth and plots the relative curve for each speaker.

The power calculator is exact arithmetic from your inputs. To reach a target SPL at distance d, the speaker first loses level over distance by the inverse-square law — about 20·log₁₀(d) dB relative to its 1 m rating (about −6 dB for every doubling of distance) in a free field. The level still needed above the 1 watt rating then comes from power as 10·log₁₀(P) dB (+3 dB per doubling of watts). Solving for power gives P = 10^((target − sensitivity + 20·log₁₀(d)) / 10) watts at the seat, and the tool also adds your chosen peak headroom so transients do not clip. Real rooms add some bass gain from room gain and boundary reinforcement, so the true power needed is often a little less than the free-field figure — treat the result as a sensible upper estimate, not a guarantee. For a standalone look at how level falls with distance, the inverse square law calculator lets you explore any source-distance combination independently.