The highest effective DF (for the purpose of damping motion of the membrane) is 1.5
It is because DF comes from dividing nominal speaker’s impedance by total impedance in the circuit. It is important to understand how damping of membrane works. When we apply positive voltage to "+" vs "-" speaker terminal membrane moves forward because of current flowing thru the coil (from + to -) in magnetic field. When membrane moves forward on its own same polarity voltage is generated on + to - speaker terminals, but current direction is opposite (from - to +), flowing from the speaker thru amplifier and back thru speaker( trying to move membrane backwards effectively braking forward motion). Speaker coil is still in the circuit and its resistive impedance is about 2/3 of nominal impedance. For that reason maximum obtainable DF is 1.5 (reciprocal of 2/3). We don’t wan’t to screw it up more so 10x lower source (amplifier) impedance is desirable. When it comes to driving varying complex speaker impedance it might be a different story, but there are many tube amps (including Atmasphere) that have DF around 1 and sound great. Searching for the amp that has DF>100 or selecting extremely thick cables is silly IMHO. On the other hand you might hear the difference, if you believe there must be a difference (placebo effect) - nothing wrong with it. If it works it works :)
It is because DF comes from dividing nominal speaker’s impedance by total impedance in the circuit. It is important to understand how damping of membrane works. When we apply positive voltage to "+" vs "-" speaker terminal membrane moves forward because of current flowing thru the coil (from + to -) in magnetic field. When membrane moves forward on its own same polarity voltage is generated on + to - speaker terminals, but current direction is opposite (from - to +), flowing from the speaker thru amplifier and back thru speaker( trying to move membrane backwards effectively braking forward motion). Speaker coil is still in the circuit and its resistive impedance is about 2/3 of nominal impedance. For that reason maximum obtainable DF is 1.5 (reciprocal of 2/3). We don’t wan’t to screw it up more so 10x lower source (amplifier) impedance is desirable. When it comes to driving varying complex speaker impedance it might be a different story, but there are many tube amps (including Atmasphere) that have DF around 1 and sound great. Searching for the amp that has DF>100 or selecting extremely thick cables is silly IMHO. On the other hand you might hear the difference, if you believe there must be a difference (placebo effect) - nothing wrong with it. If it works it works :)