[Mass. Wine Guy]

How vital is the damping factor of an amplifier? All I understand about it is that, in theory, an amp with a higher factor can control the speakers' woofers better (correct me if I'm wrong).

A used pair of Channel Audio D100 monoblocks each has a damping factor of over 1,000, while a Musical Fidelity 3.5 integrated amp's factor is around 135. Given approximately the same power, how much does damping factor matter?

Thank you.

[roscoeiii]

Depends on the speaker. A speaker can be overdamped or underdamped. I have a full range driver that I found to be overdamped by the otherwise fabulous Aleph 30. But with more conventional less sensitive speakers, this would likely be less of an issue

[Mass. Wine Guy]

Thank you.

I have a pair of Quad 12L2 speakers, 2-way, efficiency of about 88.

[richidoo]

Damping factor = Amplifier output impedance / Speaker input impedance

When an amp's damping factor is given, the hypothetical speaker impedance is assumed to be 8 ohms.
So 8/1000 = amp impedance = .025 Ohms, an excellent spec, common with class D amplifiers.

The "damping factor" is old school terminology, and kind of misleading because speaker impedance varies wildly with frequency, and few hifi speakers are nominally 8 ohms anymore, most are nominally 4 ohms. Also, adding the resistance of a speaker cable and the temporary connections at each end raise the practical output impedance when the amp is actually used. But on the test bench, where amp designers live, the output impedance is very important, and they use a 8 ohm dummy load (and other loads) to test it.

Tube amps have much higher output impedance than solid state amps, usually around 1.5 Ohms for the better quality amps that don't skimp on transformer quality. Consequently tube amps' damping factor is much lower, like 4 or 6, or even lower.

The damping factor does affect the control of the speaker, which is especially audible in the clarity and accuracy of the bass, because current is what does the work and bass frequencies demand the most power.  This is why tube amps sound "warmer" in the bass, really they just don't have the ability to provide enough current to the voice coil to force it to follow the input signal.

The output transformer winding ratio on common tube amps determines the actual output impedance, converting the high impedance of the tubes to a low source impedance suitable for driving a speaker. On OTL amps the circuit is designed to make a low impedance without transformer, using feedback to lower the impedance.

If you like clear snappy physical punchy bass, then damping factor is very important.

[bummrush]

This is another term 9 of 10 know nothing about Inc. Me but whack is used deceptively with dig amps who tout these numbers like 1000 or 2000 as selling points my amp has 75 ands it's no slouch in bass performance high number is just another number people don't know enough about

[JLM]

It's not uncommon for the combined amp/speaker pairing to be over-damped, resulting in "constipated"  sound where deep/powerful bass is missing.  OTOH under-damped combinations result in bloated/flabby sound with exagerated bass.

Classic examples of good pairings are tubes with small/sealed or horn loaded speakers and solid state with large ported speakers.  But these are just rules of thumb.

So the advent of solid state amplifiers has brought about plenty of powered subs (used with less efficient small/sealed speakers) and the loss of popularity of high efficiency horns.

[TerryO]

Damping Factor, like THD, are pretty much meaningless numbers by themselves. Bipolar transistors, back in the day, were so non-linear that they used copious amounts of negative feed-back to get the distortion down to a decent level. Negative feed-back has the effect of giving real high Damping Factor numbers, which is actually a bi-product and not necessarily a feature in itself.
BTW, Triodes are still the most linear amplification device around, need very little, or no, negative feedback and within their limits will give deeper, better bass than any Solid State A/B amplifier... if the speaker has a smooth impedance curve.

I believe that Nelson Pass, among others, has demonstrated this over the last few years.

I was sad to see Damping Factor, with it's "Iron Grip of Control" bite the dust, but the illusion was dispelled by the facts. It was like losing an old and familiar friend.

Best Regards,
TerryO

[planet10]

The damping factor does affect the control of the speaker, which is especially audible in the clarity and accuracy of the bass, because current is what does the work and bass frequencies demand the most power.  This is why tube amps sound "warmer" in the bass, really they just don't have the ability to provide enough current to the voice coil to force it to follow the input signal.

There is so much context left out of that paragraph that is could be very misleading to anyone who didn't already understand what was being talked about.

One of the key points thou its that a speaker is a current driven device.

Theoretically best bass would come from a constand current amplifier (damping factor close to zero) driving a speaker system with mechanical Q of 0.5->1.

High damping factor amplifiers are required to control speakers that have high mechanical Q (that big peak at system resonance). It does not overcome the problams associated with the speaker (with that impedance curve acting as the resistor) inbeing the I/V convertor required by a voltage source amp (amp with high damping factor).

Cutting to the chase, every loudspeaker works best with an amplifier that has an appropriate output impedance.

It is a real eye opener to have a bunch of speakers, and a variable transconductance amplifier (an amp with a knob that allows damping to be continuously variable from 0 to infinity)

dave

[Mass. Wine Guy]

Well, I confess to being even more confused than I was before I posted this. I love listening to music through good gear, but I don't understand impedance, I/V convertor required by a voltage source amp (amp with high damping factor), or lots of other concepts.

[bummrush]

Sorry AC  but go to Audio Asylum and ask  same ? and you will get a bunch of replies

[JohnR]

 

OK

[avahifi]

Actually we provided this specification way back in the late 1970s with our famous Double 400 upgrade to the Dyna ST-400.

"Damping factor:  Unit should not get wet"

Regards,

Frank Van Alstine

[Zu Audio —Sean]

Damping factor is a measure, and might help someone select a good matching amp for a loudspeaker. Generally amp/speaker matchup with regard to the damping factor spec applies or manifests in the bass. Heavy cone long through woofers that are not horn loaded nearly always benefit from an amp with a high damping factor (low output impedance). Loudspeakers that are well damped in the bass, like bass horns, may not benefit or even be over damp. Full-range driver based loudspeakers with good broadband internal electrical, mechanical and acoustic damping generally do not matchup well with amps with very high damping factor measures.

But I wouldn't get to hung up on this spec. There are lots of amp choices and this can help you narrow down your choices, but two amps that both have the same output impedance can still sound radically different, even in the bass.

To understand the root of the measure I would recommend some light reading on Voltage Source and Current Source over on wiki. This will help you get a handle on the damping factor spec. The next step would be to understand how your loudspeaker system will react to the output impedance of the amp you hand on them.

[Mass. Wine Guy]

Thanks, everyone. I appreciate your help.

[roscoeiii]

Mass Wine Guy,

It may be helpful to make this a more concrete discussion for you. What speakers are you using/considering?

As I mentioned above, the Aleph 30 was too overdamped for my 12" full range drivers (Audio Nirvanas), whereas the Atma-sphere S-30 amp I replaced it with sounds fantastic. It has a fairly low damping factor, which works great in my system(this low damping factor also relates to the amp's minimal negative feedback. Negative feedback circuitry is one way that high damping factor can be achieved which some feel may diminish sound quality). In terms of optimal bass, I have also had great luck with the FirstWatt F1 and F2 (current source amps that only work in full range driver designs lacking speaker crossovers) and both of them had low output impedance as well.

But as Sean says, damping factor is one consideration among many to consider. Good thing there are so many amp options out there...

[Quiet Earth]

Well, I confess to being even more confused than I was before I posted this. I love listening to music through good gear, but I don't understand . . . .

If you can compare two different amplifiers with an open mind and make a choice based on what you hear (not what you read), then you understand plenty.

[roscoeiii]

If you can compare two different amplifiers with an open mind and make a choice based on what you hear (not what you read), then you understand plenty.

Agreed. Though, like other amp specs and other listeners impressions, damping factor can be one factor to consider when narrowing down your options.

No substitute for listening in your own system though...

[TerryO]

Actually we provided this specification way back in the late 1970s with our famous Double 400 upgrade to the Dyna ST-400.

"Damping factor:  Unit should not get wet"

Regards,

Frank Van Alstine

Frank,

I remember that you took a "lot" of flack at the time for your inclination to ignore specs and I'm guessing that damping factor was certainly one of them. It would have been (given the understanding at the time) a pretty valid criticism, if you hadn't been designing gear that sounded so impressive.

It's pretty hard to always ignore your ears.

Best Regards,
TerryO

[planet10]

FirstWatt F1 and F2 (current source amps that only work in full range driver designs lacking speaker crossovers) and both of them had low output impedance as well.

F1/F2 have high output impedance, low damping factor.

dave

[TerryO]

Most McIntosh amps also have pretty low Damping Factor.
 

Best Regards,
TerryO