What is damping factor?

We hear about high and low damping factors for power amplifiers. But what is a damping factor, how is it calculated, and why does it matter?
Have you gotten your copy of the Audiophile's Guide to setup? Make magic with your system using this guide and CD.

[gilpena]

Thank you Paul. I really appreciate these videos and the time you spend to make them. Best on YouTube by far. Have lived in evergreen Golden Denver Lakewood Aurora Littleton and conifer. I live in fort Worth Texas at the moment but someday I'll make it back.

[c.w.johson]

I’ve been watching your videos for quite awhile now. You are one smart dude! Thanks for helping me to learn more about music reproduction.

[shpater]

Hi Paul. Thank you for your patient knowledge and experience sharing. Great Videos.
Regarding an output of an amplifier impedance, In my experience and knowledge, it should be lower such that it's presence will not be a noticeable. The actual damping impedance for the driver of the speaker is the sum of:
a. Amplifier output impedance
b. Amplifier Binding Posts (Both Plus and Minus) to speaker wires resistance ( Let's assume 0.05 Ohm)
c. Speaker cable impedance (Both Positive and Negative, lets assume 0.1 Ohm for 2 meters cable)
d. Speaker Cabinet Binding Post (Both) (Let's Assume 0.05 Ohms)
e. (In some Cheap Speakers) Speaker internal wiring ( lets assume 0 Ohm)
f. Cross Over Coils internal DC resistance (lets assume 0.2 Ohm)
g, Speaker Driver internal DC Resistance (usually few ohms, but let's assume 0 Ohms)
i. For the Woofer: Serial Coil impedance at Pass Area, i.e if upper 3dB cut frequency for the woofer is 1000Hz (for 2 order C.O), it means that coil impedance at 1000Hz is ~ 4 ohms, it means that at 100Hz Coil impedance = 0.4 ohms and 0.1Ohm at 25Hz

So by this example we see between the amplifier and the speaker added resistance /impedance of ~0.8 Ohm @ 100Hz

If my example is close to real life, it means that an output impedance of 0.08 Ohms = Damping factor of 100 is more then enough for an amplifier.

As per Feedback, too much feedback kills the Power amp slew rate (Rise time) ability. A high Slew rate is a parameter not so known or looked at, but IMHO very important indicator for the amplifier bandwidth, speaker synergy behavior and clarity.

Thanks and best regards

[glenncurry]

One of the seminars I used to give on loudspeakers and amps included demoing Damping Factor. Very easy to do. Take any speaker, the larger the woofer the better, with it disconnected from any amp, tap on the woofer cone and listen to the resonance. Then short the speaker terminals, a piece of wire, I would use my keys, and tap on the woofer. The amount of control exerted on the woofer by itself, the counter EMF allowed to flow in the completed circuit, is extremely audible. To then explain how a high damping factor means low internal resistance in the amp, like the keys shorting the terminals. And how that allows a speaker to control it's own excessive reaction to a signal.

[mannyg]

A great way of explaining it without making it complicated!

[odizcvw]

Great topic. I find these posts interesting in themselves. Often it prompts me to read further to understand the topic at a deeper level that possible in these brief videos. In this case I spent an hour reading AudioReality which covers this very well in layman's terms.

[rw]

In my old car stereo days, everyone knew Fosgate Punch and the new-comer HiFonics amps had big damping factor for that big bass hit. Then outboard caps came along with crazy subs like Sundown (sp?), which really gave the hobbyist who likes bass, something really nutty.

This is a great series; picking a speaker with high impedance can drastically lower the damping factor of an amp, so knowing speaker impedance and amp output is important, especially when it comes to low sensitivity speakers that hover around the mid 80’s dB per watt sensitivity and pairing that up with say a low output tube triode mode amp that say makes 10 and less watts per channel. Keep up the good work.

[rig]

My Bryston 3bst has a very high damping factor. It takes total control of the speaker; sound is very quick and tight. So its quite common to pair a tube preamp with them to tame them.

[willianroberts]

Does this information apply to car audio amplifiers as well

[Channel-cmyc]

So many interesting things here. But one nobody bothers to ask and it was how high is Paul’s damping factor?? hehehe it was ALMOST a joke Paul!
Great stuff keep it coming. 👍👍

[wilcalint]

Super job by Paul on this one. One way to better understand this is to connect an analog voltmeter across a cone speaker terminals and measure the changing voltage as you gently push the cone in and let it come out. The voltmeter will register the changing voltage. The amplifier has to control/sink that generated voltage/current. Also "Damping Factor" is frequency dependent. An amplifiers damping factor will be different at 60Hz than it is a 10Khz.

[NateEll]

My own anecdotal experience gained over a course of 45 years of owning one amp or another is that damping has a sweet spot, and that amps with very high damping factors just don’t sound very good. I doubt that anything over 200 or so is actually beneficial especially with speakers that have over damped low ends to begin with.

[johnvance]

Is the damping factor related to Maximum Transfer of Power in some way. When and where does matching impedandces come into play.

[magnusnielsen]

could you say that output impedance is determined by resistance through the output transistors?

[masalicio]

I love my Hegel Norway H80. It's just a baby at 75Wpc. But has 1000+ dampening factor.
All is Full of Love by Bjork can sound absolutely terrible on a lot of sub $4000 integrated amplifier's but this guy at $2000 when new in 2014 was Holy moly WOW. Absolutely no listening fatigue yet still sounds commanding/powerful!

[stevenginsberg]

I get intermittent pauses in audio only while streaming and only in surround sound. If I turn off surround and just use the TV speaker it is eliminated. Using all HDMI or ARC cables. System
Sony TV XBR 75X900H
Receiver Yamaha RX-V685
FIOS fiberoptic box
Sony BluRay
Paradigm 6 speakers including the subwoofer
Any ideas on a solution or who I can ask on what to do?
TY

[crv]

Having Paul comment/answer all these questions, i do learn alot. OTOH, reading the comments sections, one can also learn in depth what was asked....But am still lost here :-)

[allansh]

What is output impedance anyway? Which part of the circuitry has output impedance?

[ropeyarn]

The resultant listener experience with damping factor is in speaker cone control, and that means distortion, since the most distortion is introduced in the speakers. Big speaker cones at large volume with low frequencies are not easily controlled.

[stevenrayphoto]

8ohm speaker divided by .01 is 800 which is a very high damping factor for a power amp. Did you mean 8ohms divided by .1 which would be a damping factor of 80?