What is damping factor?

It’s somewhat more technically complex than this but the "damping factor" of an amplifier is usually thought of as an indicator of how "tight" an amplifier will sound when powering large bass speakers.

Here's why:

A speaker is essentially a coil of wire mounted within a magnet. As it moves within the magnet’s field of energy, a signal is induced back into the voice coil. This signal is called "Back EMF". It's essentially a voltage that has been generated by the loudspeaker itself. The larger the loudspeaker, the larger the voltage produced.

If this Back EMF is not compensated for properly in the amplifier circuitry the result is an over accentuated or boomy bass sound as the Back EMF signal tries to oppose the signal you actually want (the one from the amplifer).

Good amplifier design allows the amplifier to negate this unwanted signal and thus control the loudspeaker properly resulting in a much "tighter", controlled sound from the loudspeaker.

From a technical stand point, damping factor is a reciprocal of the amplifiers output impedance and output impedance is a derivative of the amount and implementation of negative feedback within the amplifier. Beware datasheets that state damping factor values with qualifying the frequency range. A high damping factor number is only of real use at lower frequencies as high frequency devices produce very little Back EMF.

Properly designed negative feedback not only corrects for Back EMF but also produces other benefits:

Low distortion, low noise and flat frequency response.
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