What is amplifier damping factor?

I am getting close to publishing my memoir! It's called 99% True and it is chock full of adventures, debauchery, struggles, heartwarming stories, triumphs and failures, great belly laughs, and a peek inside the high-end audio industry you've never known before.

[wilcalint]

Paul did a commendable job explaining the "damping factor" in respect to tube amps. The effective resistance of the output transformer results in a low damping factor and less "control" of the speaker load.

Speakers are electromagnetic devices. Effectively they are motor generators. When the amp delivers energy to the speaker it can expect to receive energy back ( cone overshoot and generating energy ) and it's ability to sink that energy will effect the sound. Amplifiers with high damping factors should effectively sink a lot of energy. I like to think of it as the big strong hand of the amp grabbing a hold of the speaker.

I am the happy owner of a dual chambered subwoofer with a 16in Altec Lansing theater driver in it. A few years ago I married it to a bridged Crown XLS1000 amp that has a high damping factor ( >200 ), 8ohms, 10Hz -> 400Hz. I could clearly hear that the amplifier made a big improvement in the "control" of that big electromagnetic motor.

[garywells]

A friend who worked as an audio salesman in the mid seventies brought an Accuphase power amp home to try out. On the front panel there was a 3 or 4 position switch that allowed the user to change the damping factor of the amp. The lowest setting, as I recall, was 60. I don't recall what the highest was, but nevertheless, the lower damping factor sounded better. Since then, I have always chosen amps with damping factors of no more than 100.

[janinapalmer]

Damping factors .... YES !!
One of my pet topics .... Paul is roughly right here here ... he didn't explain where the figure actually comes from though ... it's derived from the output source impedance divided into the speaker impedance . In tube amplifiers it's the same .. in the days of tube amplifiers ( pre solid state ) most speakers had an impedance of 15-16 Ohms .. this high impedance was to get a higher damping factor . It must be noted here that a loudspeaker system with a passive dividing network will have an impedance curve that is not 100% flat .. it will go up and down in value and hence the DF will vary too.

[johnyang]

Cable must be considered as well. High damping factor will be masked by the impedance of cable.

[gotham]

The problem is that a high damping factor is often achieved by applying lots of negative feedback, and it is this which kills the sound.

[zulumax]

What an interesting and unusual topic.
Think of damping as an electronic shock absorber for your speakers. Bandwidth and frequency of damping is important, but mostly in the lower bass. An Adcom GFA-565 mono block has a damping factor of 1000. Early 70's transistor receivers have damping as low as 10, while my Heathkit W5M tube mono block amps have an unusually high damping factor of 40 which is high for a tube amp. Dynaco ST-70 has a damping factor of 11. Average is probably around 250 in my experience in modern transistor gear. Many factors effect damping, negative feedback, speaker wire, final output design, topography, and bias. 50Hz is common standard frequency used to measure damping factor. High damping factor good for subs, but can cause midrange to sound too sterile and lifeless in full range. Damping factor is the poor mans servo woofer in effect. These are my opinions of course, and am interested in what others experiences have been.

[JohnAudioTech]

A typical speaker with a nominal 8 ohm impedance will have a DC resistance of around 6 ohms. This resistance is electrically in series with the amplifier and reactive part of the speaker essentially swamping the high damping factor of the amplifier. Even the speaker wire will swamp the high damping factor of the amplifier. If the speaker wire has a resistance of 0.2 ohms, it would reduce the effective damping factor to around 40.

[salvadorrodenas]

Very well unexplained, not always is the case Paul.

[billwilliams]

why does the power amplifier output impedance cause the damping factor to increase or decrease? what else can cause the damping factor to increase and decrease?

[paulrs]

Yes, most of our experience says that high-end speakers sound better (mostly a wider, deeper soundstage) when driven by an amplifier with low to moderate damping factor, say 5-10. Bob Carver did have an interesting theory why this is the case. And yes, much depends on how good an amplifier's specs are BEFORE negative feedback is applied. Some, both tube and solid state, are good without feedback.

[scottjohnson]

Enter in the now discontinued CROWN REFERENCE SERIES 1
Damping factor of 20, 000 a beast of an amp ! Don't try to lift it by yourself

[royferntorp]

This answer has got me asking, how do you measure speaker impedance? Audio is AC but our multimeters measure in DC. Please explain.

[CraigFlowersMusic]

So the Carver M-1.0t has a damping factor of about 8, and says "Low Feedback High Gain" on the faceplate. I didn't know these were related. Why then does IT sound so relatively good with such a low damping factor?! Tube amplifiers have high impedance. I have a Sunfire which has two different kinds of outputs; one of which is around 1 ohm impedance to, apparently, mimic a valve amp. This all flies in the face of convention, so why is that?

[TheUnrevealer]

Naim amps, even higher range ones, also have relatively low damping factor, but they controll speakers well.

[ProDigit]

The Eden WTX260 has a damping factor of 5000.
I imagine it matters more to bass guitar amplifiers, than to mid or high frequency amps?
The amp only goes down to 4 Ohms (I tested it at 3.33Ohms, but 2 ohms and it went into protection mode), but David's later amps ran 2 ohms just fine!

[carolineleonard]

Have a listen to Hegel's H360 and H590. Damping factor in excess of 4000. They sound fantastic. I'd say reference quality, depending upon your preferred audio taste of course.

[jonathansturm]

An engineer who isn't very good at mathematics? You have my sympathy; my brother got all dad's mathematical genes... Worth noting that Class D also struggles a bit regarding damping factor, not just hollow state.

[patrickalphenaar]

My XTZ Edge a2-300 PowerAmp has a >1500+ Damping Factor and you hear that so clearly in all frequencies! With its class D Technology and 150 Watts at 8 Ohm its my favorite Amp and is only 495 euro, meaning High-End doesnt always need to Expensive. Cheers.

[Cartier_specialist]

My NAD has a damping factor of 110. I'm guessing that's pretty darned good because it has enormous headroom according to the spec sheet but fortunately I don't listen to spec sheets I listen with my ears.

[airgead]

Paul, please read my comment elsewhere where I explain that the damping factor is the bogus factor. I am curious about your thoughts about my explanation.