Damping Factor
Definition
Damping factor describes how well an amplifier stops a speaker cone after a signal transient ends. It is the ratio of the speaker's nominal impedance to the amplifier's output impedance. Higher damping factor generally means tighter, more controlled bass.
Formula
damping factor = speaker nominal impedance / amplifier output impedance
Example: an 8Ω speaker with a 0.08Ω amplifier output impedance has a damping factor of 100.
Speaker cable resistance adds to the effective output impedance. Long or thin cable lowers the damping factor the speaker actually sees.
In a stereo system
Treat damping factor as secondary to impedance stability. A correct 4Ω or 8Ω match matters more than chasing a high published damping figure.
As a rough guide:
- DF above 50: typically well controlled
- DF below 20: bass may sound looser, depending on the speaker's mechanical damping
Solid-state power amps usually publish high damping factors. Tube amps often publish lower ones and still sound controlled if the speaker is a good match.
