tonistry.

Specs & measurements

Damping factor

Also called DF

Damping factor is a speaker’s impedance divided by the amplifier’s output impedance, a measure of how firmly the amplifier controls the speaker cone’s movement. Values above about 20 are considered adequate; the very high figures on some spec sheets add little.

Solid-stateDF 808 Ω speaker0.1 Ω output × 80 = 8 ΩTube ampDF 48 Ω speaker2 Ω2 Ω2 Ω2 Ω output × 4 = 8 Ω
Damping factor is the speaker’s impedance divided by the amplifier’s output impedance: a 0.1 Ω output fits into an 8 Ω speaker 80 times, so the damping factor is 80. A 2 Ω tube output fits four times, a single-digit damping factor of 4.

An 8 Ω speaker driven by an amplifier with 0.1 Ω output impedance has a damping factor of 80. Low damping lets the woofer ring after a note, heard as loose or boomy Bass. Speaker cable resistance counts too, which is why thin, long runs lower the effective figure.

Figures in the thousands are marketing; the speaker’s own voice-coil resistance limits what any amplifier can do. Tube amplifiers often have single-digit damping factors, and the softer bass that results is part of their sound.

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