Amplifier damping factor above 20 produces no audible effect on loudspeaker transients

Evidence

Obviously the resistances inside the loudspeaker are the dominant factors. Even eliminating the inductor and driving the woofer directly changes things only slightly. The article (Toole, 1975) shows oscilloscope photographs of tone bursts of various frequencies and durations while the damping factor of the amplifier was varied from 0.5 to 200. At damping factors above about 20 (internal impedance less than 0.4 ohms), no change was visible in any of the transient signals, and changes in frequency response were very much less than 1 dB, and then only over a narrow frequency range. On music no change in sound quality could be discerned, including attentive listening for “tightness.” Because 0.4 ohms is at least a factor of 10 higher than internal impedances found in typical solid state amplifiers, it means that, from the perspective of damping the transient behavior of loudspeakers, the wire resistance can be allowed to creep up substantially. However, as shown earlier, doing so can change the frequency response of the loudspeaker and that, we know, is audible. — , Toole, Floyd E - Sound reproduction-…, 1782

Categorization

• CANDY: A short, tweetable myth-busting fact: damping factor above 20 is inaudible, and a factor of 10 higher than solid-state amps actually deliver.
• DEFINE: Explains what damping factor means and why the common ‘bigger is better’ assumption fails.
• XREF: connects to: Low diaphragm mass does not improve transient response in panels; Damping factor varies from 200-800 for solid-state but only 2-11 for tube amps — , Toole, Floyd E - Sound reproduction-…, 1779

Related

• Damping factor varies from 200-800 for solid-state but only 2-11 for tube amps (similarity 0.88)
• Tube amplifiers sound different mainly because their high output impedance alters loudspeakers (similarity 0.83)
• Low diaphragm mass does not improve transient response in panels (similarity 0.82)
• Sub-2-ohm speaker designs caused the amplifier differences reviewers praised (similarity 0.80)
• Badly designed loudspeakers cause audible amplifier differences reviewers attribute to the amplifiers (similarity 0.80)
• Audible distortion in quality loudspeakers is rare within intended limits (similarity 0.80)
• Published loudspeaker impedance ratings rarely represent actual frequency response (similarity 0.80)
• Distortion rarely drives subjective ratings of consumer loudspeakers (similarity 0.79)
• Well-damped low-Q resonances are easier to hear than high-Q ones. (similarity 0.79)
• Speaker wire resistance is negligible compared to tube amplifier output impedance (similarity 0.79)
• Loudspeaker rated impedance figures are largely invented marketing numbers (similarity 0.78)
• Resonant power dissipation actually grows when damping decreases (similarity 0.78)

Broader Connections

• Damping factor varies from 200-800 for solid-state but only 2-11 for tube amps #expands (0.85) — , Toole, Floyd E - Sound reproduction-…, 1779