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Damping Factor/ WPC

furnitureguy

furnitureguy

Active Member
I am a bit confused by "damping factor". A very brief explanation I came across stated it as the ability of the amp to control the speakers.
It’s been my experience that adding a lot of power to the equation (many more watts per channel) seems to dramatically increase the amps ability to control and define the sound.
Increasing the wattage from 85 (Marantz 2285b - damping factor 60) to 185 (Marantz 2385- damping factor also 60) has a dramatic effect on my AR-10pi's and Allison one's. The music comes alive and on good recordings each individual instrument seems to be acutely defined.
So - is this extra definition achieved by the added wattage similar to the effect of damping? Could I get the same effect by finding an amp with a higher damping factor? Or do I not understand "damping factor"?
 
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Damping factor is more a function of amp design than power rating. It refers to the amp's ability to halt woofer movement immediately after it's no longer desired. From what's I've read, DF should be a minimum for 20-30 for hi-fi- anything more is fine but not necessary.
 
Damping Factor is a term that by it's designation seems to suggest all sorts of things that, actually aren't involved. As a figure of merit it's nearly worthless and is more of an incidental by-product of negative feedback than being any sort of positive design feature. Here's what (I believe) gives some real insight into the realm of what those high damping factors actually mean in the real world.

AK's Dave Newman (dnewma04) wrote:

Let's do some math.

We know that damping factor is a ratio, specifically, it's the load impedance divided by the output impedance of the amplifier. For now, we'll ignore how amplifiers attain low output impedance just for the sake of simplicity.

So, let's say we have an amplifier with a damping factor of 2000 and an impedance of 8 ohms.

DF = Load Impedance / Output Impedance

2000 = 8 / Output Impedance

Output Impedance = .004

All is well in the world, right? We have our staggeringly high damping factor but we've ignored something important.

We forgot to include the series resistance of the speaker wire between the amp and speakers. Let's redo the calculation now.

Again, we know that DF = Load Impedance / Output Impedance, but now we are going to add in the effects of the speaker wire into our equation to figure out what the "real" or "effective" damping factor is of the real world situation. For simplicity sake, we'll err on the side of caution and say that it's very low resistance wire and only presents a .1 ohm load.

DF = 8 ohm / (.004 ohm + .100 ohm)
DF= 8 ohm / .104
DF= 76.9

The advertised damping factor of 2000 is now only 77 at the terminals of the speakers.

Now, let's look at what is going on at the terminals of the woofer in a speaker system with a passive crossover.

It's not unusual to have a series resistance of 1 ohm in a passive crossover, but just for a best case scenario, let's say that it's only .25 ohm.

DF = 8 / (.004 + .100 + .250)
DF = 8 / (.354)
DF = 22.6 at the woofer.

Now, let's say the damping factor of the amp is 20000! Surely that must make a huge difference being an order of magnitude higher than 2000!

Unfortunately, the reality is:

DF = 8 / (.0004 + .25 + .1)
DF = 22.8

It's essentially the same.

Now, let's say that the amplifier in the same scenario is only at 50.

DF = 8 / Output impedance

50 = 8 / Output Impedance

Output Impedance = .16

Now that we have the output impedance of the amp with a DF of 50, let's substitute into our scenario to see the DF at the woofer:

DF = 8 / (.16 + 1 + .25)
DF = 8 / (.51)
DF = 15.7



Do you see how most people just don't find DF that important? In the real world, the difference between a low DF amp and a ridiculously high DF amp is essentially moot at the woofer.
Click to expand...

Best Regards,
TerryO
 
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It is exactly as TerryO said; no more and no less than a ratio of a nominal load impedance to the output impedance of an amplifier. Since very few speakers present perfect resistive loads (or, more specifcally, have completely flat impedance as a function of frequency), a single DF number's pretty abstract from real world issues.

FWIW, I consider it (the nominal damping factor) virtually meaningless - as the means sometimes used to reduce output impedance are far more detrimental than would be a slightly higher output impedance.
 
The wikipedia entry explains it fairly well. Read the section under explanation.

http://en.wikipedia.org/wiki/Damping_factor

Now quite honestly, I've never heard an audible difference. I suspect you most likely wouldn't unless under controlled conditions, (such as a test tones,) and again, quite honestly, I'm not *THAT* critical of a listener...
 
+1 to what Terry said.

The interaction between the amp and the speaker is extremely complex. I have speakers which produce wildly different output depending on the amp driving them. And it has NOTHING to do with DF as far as I can tell.

Cheers, Jim
 
Last Summer, or was it the year before (?), one of the guys at the Vancouver Island DIY Fest had built a variable DF amplifier that, with the twist of a knob, could change the DF from essentially zero to some unbelievable number. We had a lot of fun with it and found that the lower settings (near zero) produced "much" better bass. I'd say that it was substantial, hard-hitting, with no residual ringing, lag or lack of driver control at all, which is contrary to what some well-meaning, but misguided, souls would have you believe.

Best Regards,
TerryO
 
I should have taken the time to say:

The worst match I have had is a Yamaha CR-1000 with Fostex F120A in Metronomes. This combo has very poor high freqs and the mids are so-so. Change over to a Sansui 4000 and the sound is very nice. Now switch to a tube amp, and it's absolutely magic! In each case the bass is fine, the difference is greatest in the highs, somewhat less in the mids.

Both the SS units have high DF. The obvious difference between them is that the Yamaha is direct coupled output, while the Sansui is cap coupled. And the tubes are a whole other story....

You just need to find the right synergy.

Cheers, Jim
 
Jim Shearer said:
I should have taken the time to say:

The worst match I have had is a Yamaha CR-1000 with Fostex F120A in Metronomes. This combo has very poor high freqs and the mids are so-so. Change over to a Sansui 4000 and the sound is very nice. Now switch to a tube amp, and it's absolutely magic! In each case the bass is fine, the difference is greatest in the highs, somewhat less in the mids.

Both the SS units have high DF. The obvious difference between them is that the Yamaha is direct coupled output, while the Sansui is cap coupled. And the tubes are a whole other story....

You just need to find the right synergy.

Cheers, Jim
Click to expand...

Jim,

You're certainly correct about seeking the ideal synergy. It's been written many times that tubes have no place in a serious system due to, among other things, that they don't have enough damping factor which results in "flabby" bass. McIntosh amplifiers (both tube and SS) have very low damping factors and I've never seen them criticised for having poor bass output. Likewise, both Nelson Pass and Frank Van Alstine have designed absolutely superb amps and have pretty much ignored Damping Factor altogether.

The whole thing about Damping Factor is a holdover from the late 60's and mid 70's, but unfortunately it seems to have caught people's imagination and like Dracula, refuses to die!

Best Regards,
Terry
 
I've had many an argument over damping factor, mostly on a car audio board I used the frequent. Many people think it's as important as the amount of output power. I never have figured out why this particular spec stands out to people as important.
 
62caddy said:
Damping factor is more a function of amp design than power rating. It refers to the amp's ability to halt woofer movement immediately after it's no longer desired. From what's I've read, DF should be a minimum for 20-30 for hi-fi- anything more is fine but not necessary.
Click to expand...
.....I'll go with 62Caddy on this....anybody have a McIntosh MC2105 which has a damping factor of 10?.....
 
^^^
No, but I have an Audio Research 100.2 amp with rated DF of 20. It's a damn fine sounding amp, IMO. No problems whatsoever with flabby bass.
 
mulester7 said:
.....I'll go with 62Caddy on this....anybody have a McIntosh MC2105 which has a damping factor of 10?.....
Click to expand...

According to the owner's manual, the McIntosh 2105 has a Damping Factor of:

13 @ 8 ohms output
18 @ 4 ohms output
10 @ 16 ohms output

I might add that using Dave Newman's generic numbers, I calculated an "effective" DF of 12.97 @ 8 ohms, beginning with a nominal DF of 30.

For many years McIntosh wouldn't allow the Audio Magazines to test their amplifiers, probably because they would have been declared a bad design due to insufficient Damping Factor.

Just the same, even today many people still seem to think that it's a viable spec.

Best Regards,
TerryO
 
whoaru99 said:
^^^
No, but I have an Audio Research 100.2 amp with rated DF of 20. It's a damn fine sounding amp, IMO. No problems whatsoever with flabby bass.
Click to expand...
.....I figured you'd show up on a damping factor thread :D....flabby bass....does that mean a ringing bass?....I don't have it in the present mix, but something surely sounds different using my MC2105....to me, it gives a tubey sound overall....does the simply worded explanation section from Wikipedia mean nothing?....doesn't it say the measured damping factor indicates the control an amp has over the speaker element cones?.....

http://en.wikipedia.org/wiki/Damping_factor
 
mulester7 said:
.....I figured you'd show up on a damping factor thread :D....flabby bass....does that mean a ringing bass?....I don't have it in the present mix, but something surely sounds different using my MC2105....to me, it gives a tubey sound overall....does the simply worded explanation section from Wikipedia mean nothing?....doesn't it say the measured damping factor indicates the control an amp has over the speaker element cones?.....

http://en.wikipedia.org/wiki/Damping_factor
Click to expand...

Actually, the part in the linked Wikipedia article (with my emphasis) that caught my eye is:

Over a range from less than 1 to up to around 50, damping factor describes the ability to which the amplifier helps to control the oscillation of the speaker, expressing the degree to which the amplifier does not exert a resistance against the current generated by the speaker. A damping factor of 50 is high, indicating that the output impedance of the amplifier is negligible compared to the internal resistance of the speaker and the speaker cabling.

Higher electrical damping of the loudspeaker is not necessarily better. Some loudspeakers sound better with lower electrical damping. A lower damping factor helps to greatly enhance the bass response of the loudspeaker, which is useful if only a single amplifier is used for the entire audio range. Therefore, some amplifiers, in particular vintage amplifiers from the 1950's, 60's and 70's, feature controls for varying the damping factor.
Click to expand...

Best Regards,
TerryO
 
TerryO said:
For many years McIntosh wouldn't allow the Audio Magazines to test their amplifiers, probably because they would have been declared a bad design due to insufficient Damping Factor.
Click to expand...
.....that's speculation on your part, Terry....McIntosh surely sold a ton of 2105's, and they're still highly sought after.....

TerryO said:
Just the same, even today many people still seem to think that it's a viable spec.
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.....and, I'm one of those people, even though I guess I'm just a poor misguided wretch like you referred to earlier :D....these Crown K2's I've got are exceptionally tight and crisp, top to bottom....the damping factor of a Crown K2 is >3000 from 10 to 400 hz....is there an amp which has a higher DF than that?....when I'm listening to a system, the LAST thing I'm going to do afterwards is go do math to see if what I heard was possible.....
 
Yup, sure are. Crown Studio Reference and Macro Reference sport DF of >20,000. I've seen some other high ones too but don't recall them off hand. Those were sorta hard to forget with that number.

The problem with comparing DF numbers from gear to gear is same problem, IMO, in a lot of comparisons. You don't have a Amp 1 and Amp 2 that are the same in all regards except for DF to know if that is really the deal or not. And, you can't really consider just the effect of controlling cone motion because the effect on overall frequency response probably outweighs any difference in damping. This is the primary effect Audioholics concludes, not the bit about cone motion.

You could experiment though by merely adding speaker cable which changes high DF a lot. That was the point of the formulas early on in the thread. The amp may have DF of >3000, but by the time you factor speaker wire it's typically much less. The higher the damping factor the more easily it is knocked down to normalcy by the added resistance of speaker wire. IOW, the higher you are the further the fall.
 
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whoaru99 said:
Yup. Wiki says that, but this http://www.audioholics.com/education/amplifier-technology/damping-factor-effects-on-system-response puts a bit more technical/scientific detail behind their material, rather than merely talking points.
Click to expand...

I've found anything written by Dick Pierce (an unfortunately painful name) to be worthwhile.

I remember in the mid-70's that TAS declared the audio equivilent of the second coming when an unknown young designer released a new preamp design. Issue after issue was crammed full of praise for this young genius, until Dick Pierce pointed out that the "entire" design had been lifted straight out of National Semiconductor's App Notes!
There were, understandably, a lot of red faces at TAS and it took a long time to get over that gaff.

Best Regards,
Terry
 
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