Hi,
electrical damping happens as the driver back-EMF voltage makes current in the circuit over the impedance in series with the voice coil. This current then opposes the movement, the driver dampens itself as long as there is low impedance path between driver terminals at the drivers resonant frequency. If you have an L-pad there, analyze there circuit from drivers perspective, replace amplifier with resistor equal to its output impedance for simplicity. Usually the amplifier output impedance is so low that its basically a short. Whats left is the L-pad resistors in parallel which makes perhaps few ohms. This is in series with the voice coil impedance which we can do nothing about so the L-pad reduces maximal damping a bit. Maximal damping would happen when there is very low impedance between driver terminals, in other words a "high damping factor" amplifier, almost a short circuit for the back-EMF.
Here is nice article how amplifier damping factor, or more accurately the output impedance, works with a driver: https://www.edn.com/loudspeaker-operation-the-superiority-of-current-drive-over-voltage-drive/ please ignore title of the article as its somewhat provocative, but the content and math is nice and simple to understand I think. Basic thing to get from the article is that the electrical damping is useful only at drivers main resonance, but above that it doesn't deliver and increases distortion in acoustic domain instead. Main message being, low circuit impedance in series with voice coil is useful around drivers main resonance, but above that we could very well raise the impedance to reduce distortion current from driver motor non-linearities to enter acoustic domain. Circuit impedance is not just the amplifier output but also the passive electronics and cabling in between. Any amplifier output impedance is workable, if electrical damping is needed a parallel network can be used. Easiest is to analyze the load impedance for driver and take advantage of it, low for resonance, high above.
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Excellent myth busting article. The following excerpts sum up the irrelevance of damping factor:
"The supposed justification for the status quo of voltage drive lies mostly, if not entirely, in the widely shared belief and refrain that voltage “controls cone motion” as if by some miraculous iron grip that is the result of high “damping factor.” In light of any valid engineering analysis, however, the belief amounts to total nonsense..."
and
"The delusion of “damping factor”
According to a rampant myth, a high “damping factor” (ratio of nominal load impedance to amplifier output impedance) is needed to deal with the back-EMF, to prevent who knows what errors from happening in the amplifier or the feedback loop, and of course, to control cone motion. (The quotation marks have been used because it is an artificial metric created for marketing purposes and not deriving from any relevant operational equations.)"
"The supposed justification for the status quo of voltage drive lies mostly, if not entirely, in the widely shared belief and refrain that voltage “controls cone motion” as if by some miraculous iron grip that is the result of high “damping factor.” In light of any valid engineering analysis, however, the belief amounts to total nonsense..."
and
"The delusion of “damping factor”
According to a rampant myth, a high “damping factor” (ratio of nominal load impedance to amplifier output impedance) is needed to deal with the back-EMF, to prevent who knows what errors from happening in the amplifier or the feedback loop, and of course, to control cone motion. (The quotation marks have been used because it is an artificial metric created for marketing purposes and not deriving from any relevant operational equations.)"
Thanks for the very intuitive explaination!
I’m sure this has been answered before, but can the human ear “hear” damping factor. Has anyone actually done a A/B test of this?
I’m mostly coming from a valve instrument amplifier perspective.
Depending on your speaker it could be from no difference to quite obvious, a bump in frequency response where driver main resonance is and severity would depend on the impedance of the amp output and impedance of the driver, which reflects how much acoustic/mechanical damping there is. The missing electrical damping could be replaced with enclosure damping,at least partly, or just with EQ. A notch filter somewhere taking down the response peak.
If a speaker relies on the electronic damping and you'd swap between high or low output impedance amplifier (low or high damping factor) directly connected to it you'd hear a peak in the response come and go. System Q would change. Qts'
If a speaker relies on the electronic damping and you'd swap between high or low output impedance amplifier (low or high damping factor) directly connected to it you'd hear a peak in the response come and go. System Q would change. Qts'
The low damping factor of a valve amp causes it to react more to the speaker's changing impedance, resulting in a 'looser' playing feel.
Also, the transition from clean to distorted sound is less abrupt allowing the amp to transition more smoothly into distortion.
Best I've seen is what's on my subs currently which is a total of 12 10 gauge leads per subwoofer /spider pack although when I reconnect them I'm going to try 4 25mm leads to see if they handle the power better or if they still end up burning in the 5000ish rms range
Damping factor is a real issue, but once you get over 20 or so, then it's just advertising copy, where more is better, needed or not.
Same with distortion. .01% is quite sufficient. Slew rate , IMD , overload behavior are are more important.
Long term stability , ease of repair are notable. NO "fluff" (PMPO) ... be modest !
Long term stability , ease of repair are notable. NO "fluff" (PMPO) ... be modest !
Regarding how much distortion you can hear, Klippel have a listening test to see how much distortion you can perceive using music https://www.klippel.de/listeningtest/