Acoustic Power Efficiency
Loudspeaker efficiency (η):
η = P_acoustic / P_electrical
Sensitivity and efficiency relationship:
η ≈ 10^((Sensitivity − 112) / 10)
| Sensitivity (dB/W/m) | Efficiency |
|---|---|
| 85 | 0.03% |
| 88 | 0.06% |
| 91 | 0.12% |
| 94 | 0.25% |
| 97 | 0.50% |
| 100 | 1.0% |
From Thiele-Small parameters:
η₀ = (4π² / c³) × (f_s³ × Vas / Qes)
Simplified:
η₀ ≈ (9.64 × 10⁻⁷) × (f_s³ × Vas / Qes)
Where Vas in liters, f_s in Hz.
Worked example:
Subwoofer: f_s = 35 Hz, Vas = 50L, Qes = 0.5
η₀ = (9.64 × 10⁻⁷) × (35³ × 50 / 0.5)
η₀ = (9.64 × 10⁻⁷) × (42,875 × 100)
η₀ = (9.64 × 10⁻⁷) × 4,287,500
η₀ = 0.00413 = 0.41%
Sensitivity at 1W/1m:
Sensitivity = 112 + 10 × log₁₀(0.0041) = 112 − 23.8 = 88.2 dB/W/m