High Damping Factor and Bass Output

[Buckeyefan 1]

Taken from "Secrets"

Damping Factor

The impedance of the speaker will also affect what is known as the "damping factor". This is defined as the ratio of the impedance of the speaker to the output impedance of the amplifier. Thus, if the speaker impedance is 8 Ohms, and the amplifier output impedance is 0.05 Ohms, then the damping factor is 8 divided by 0.05 = 160. High damping factors usually mean that the bass response will be well defined ("tight"), whereas a low damping factor will result in a loose sounding bass. Tight or loose bass is from an amplifier is not a matter of preference. A low damping factor on an amplifier implies a high output impedance, which means that the frequency response of the amp can change by reacting to the changing impedance of the speaker it drives, making results unreliable. The bass is just one area that might suffer from a low damping factor, as it can also adversely affect other frequencies where a speaker's impedance isn't flat. Some tube amplifiers may have low damping factors, for example, 10, compared to solid state, which may contribute to their typically loose bass response (tube amplifiers are often described in terms of "warmth" or "looseness", and it can be a very pleasant effect). Such an effect may be very pleasurable, but it's also a good guarantee that you're not hearing what the loudspeaker designer created. In any case, the specification sheet for the amplifier will sometimes list the damping factor, but so long as it's above 70 or so, it's not really a real world issue.

Here's the full article - http://www.hometheaterhifi.com/volume_1_1/index.html

So what's everyone's take on this explanation? Hopefully we can hear from Wmax, Mtrycraft, Mulester, MacManNM, and some others.

Here's an article from Audioholics on the topic:
http://www.audioholics.com/techtips/audioprinciples/amplifiers/dampingfactor.php

...and the conclusion

"There may be audible differences that are caused by non-zero source resistance. However, this analysis and any mode of measurement and listening demonstrates conclusively that it is not due to the changes in damping the motion of the cone at the point where it's at it's most uncontrolled: system resonances. Even considering the substantially larger response variations resulting from the non-flat impedance vs. frequency function of most loudspeakers, the magnitude of the problem simply is not what is claimed.

Rather, the people advocating the importance of high damping factors must look elsewhere for a culprit: motion control at resonance, or damping, simply fails to explain the claimed differences."

 

[WmAx]

.....

It's a subject blown out of proportion. It is in net effect an equalization effect.

This is basic electric behaviour. Nothing more. If you have a high source impedance, the voltage delivered by the source is reduced at lower load resistance, while it remains constant at high load resistance. This is true even with low source impedance, but the change in voltage in the circuit is smaller, the lower the source impedance. So, give a combination of a high enough source impedance(this is what low dampening factor is) and a dynamicly changing load(impedance) with sufficient difference, and the voltage difference when delivered into the high point of the load impedance vs. the low point of the load impedance will become significant enough to create an audible equalization curve.

BTW, you can make any low output source impedance act exactly like a high source impedance by inserting resistance in series with the load. You can do this with a resistor or with very small diameter wire.

It takes a poorly designed amplifier to have a high enough source impedance to create audible frequency response differences. There is no inherant reason even for tube amps to do this, as the designer can use an appropriate output transformer to have a low enough source impedance if they so choose.

-Chris

 

[Resident Loser]

As I understood it...

...damping factor was the amp's ability to control driver motion...simply to "damp" it's excursion as the signal would dictate and that it was somehow tied to square-wave response, ring, overshoot and the like...the higher the number being better for more "accuracte" overall performance, due to a better electro-mechanical "coupling" of the two components.

While the mechanics behind it may have something to do with impedance, I don't see how it's an equalization effect , at least insofar as I understand the word.

jimHJJ(...but then again, I've never really claimed to know very much anywho...)

 

[WmAx]

While the mechanics behind it may have something to do with impedance, I don't see how it's an equalization effect , at least insofar as I understand the word.

jimHJJ(...but then again, I've never really claimed to know very much anywho...)

The driver's mechanical movement(dampening) difference is because of the frequency response difference caused by the electrical reaction I described in my first post. When you change the frequency response curve(apply a peak in response for example), you affect the phase and amplitude of that response, which in turn dictates the time and frequency domain characteristics of that response. In fact, as I stated how you could force poor dampening factor behaviour(using a resistor) on a system that had good dampening factor behaviour, you can also force a poor dampening factor to sound like a high dampening factor system by using a parametric equalizer to apply (an) inverse correction curve(s) to counteract the initial curve(s). You can also force the high dampening factor system to behave like the poor dampening factor system via a parameteric equalizer.

-Chris

 

[MacManNM]

Taken from "Secrets"

Damping Factor

The impedance of the speaker will also affect what is known as the "damping factor". This is defined as the ratio of the impedance of the speaker to the output impedance of the amplifier. Thus, if the speaker impedance is 8 Ohms, and the amplifier output impedance is 0.05 Ohms, then the damping factor is 8 divided by 0.05 = 160. High damping factors usually mean that the bass response will be well defined ("tight"), whereas a low damping factor will result in a loose sounding bass. Tight or loose bass is from an amplifier is not a matter of preference. A low damping factor on an amplifier implies a high output impedance, which means that the frequency response of the amp can change by reacting to the changing impedance of the speaker it drives, making results unreliable. The bass is just one area that might suffer from a low damping factor, as it can also adversely affect other frequencies where a speaker's impedance isn't flat. Some tube amplifiers may have low damping factors, for example, 10, compared to solid state, which may contribute to their typically loose bass response (tube amplifiers are often described in terms of "warmth" or "looseness", and it can be a very pleasant effect). Such an effect may be very pleasurable, but it's also a good guarantee that you're not hearing what the loudspeaker designer created. In any case, the specification sheet for the amplifier will sometimes list the damping factor, but so long as it's above 70 or so, it's not really a real world issue.

Here's the full article - http://www.hometheaterhifi.com/volume_1_1/index.html

So what's everyone's take on this explanation? Hopefully we can hear from Wmax, Mtrycraft, Mulester, MacManNM, and some others.

Here's an article from Audioholics on the topic:
http://www.audioholics.com/techtips/audioprinciples/amplifiers/dampingfactor.php

...and the conclusion

"There may be audible differences that are caused by non-zero source resistance. However, this analysis and any mode of measurement and listening demonstrates conclusively that it is not due to the changes in damping the motion of the cone at the point where it's at it's most uncontrolled: system resonances. Even considering the substantially larger response variations resulting from the non-flat impedance vs. frequency function of most loudspeakers, the magnitude of the problem simply is not what is claimed.

Rather, the people advocating the importance of high damping factors must look elsewhere for a culprit: motion control at resonance, or damping, simply fails to explain the claimed differences."

This is one of those things that can help separate the men from the boys in amplifiers. I have seen very poorly designed units that exhibit these characteristics. This is also one of those things that you can’t always tell from spec sheets. This is why a good amp, like my Proton, is so much better than something like an Insignia receiver from best buy.

 

[MacManNM]

The driver's mechanical movement(dampening) difference is because of the frequency response difference caused by the electrical reaction I described in my first post. When you change the frequency response curve(apply a peak in response for example), you affect the phase and amplitude of that response, which in turn dictates the time and frequency domain characteristics of that response. In fact, as I stated how you could force poor dampening factor behaviour(using a resistor) on a system that had good dampening factor behaviour, you can also force a poor dampening factor to sound like a high dampening factor system by using a parametric equalizer to apply (an) inverse correction curve(s) to counteract the initial curve(s). You can also force the high dampening factor system to behave like the poor dampening factor system via a parameteric equalizer.

-Chris

All the money and time you are going to spend on equipment to set up any kind of reasonable correction, you might as well go and buy a decent amp in the first place! Then on top of it, you have electrical characteristics that change over time, and the changes in the corrected equipment is going to be much more noticeable than the unit that didn't need correction in the first place.

 

[mtrycrafts]

Taken from "Secrets"

Damping Factor

I can draw your attention to this part of the article:
Secondly, the effects of this loss of damping on system frequency response is non-existent in most cases, and minimal in all but the worst case scenario. Using the criteria that 0.1 dB is the smallest audible peak, the data in the table suggests that any damping factor over 10 is going to result in inaudible differences between that and one equal to infinity. It's highly doubtful that a response peak of 1/3 dB is going to be identifiable reliably, thus extending the limit another factor of two lower to a damping factor of 5.



This is what would be audible, level changes, but in the low driver this .1dB which is not the criteria for audibility just level matching components when comparing, is not even close to the low frequency JND threshold.
Much is made of DF, not much meat behind them.

REFERENCES


(1) James Kraft, reply to "Amplifier Damping Factor, Another
Useless Spec," rec.audio.high-end article
2rcccn$...@introl.introl.com, 24 May 1994.


(2) A. Neville Thiele, "Loudspeakers in Vented Boxes," Proc. IRE
Australia, 1961 Aug., reprinted J. Audio Eng. Soc., 1971 May
and June.


(3) Richard H. Small, "Closed-Box Loudspeaker Systems," J. Audio
Eng. Soc., Part I: "Analysis," 1972 Dec, Part II, "Synthesis,"
1973 Jan/Feb.

 

[mulester7]

.....I'll say this....a fair way to AB the damping factors of two amps is one pushing the rears, and the other pushing the fronts....it's best if all four speakers are the same, but mids is where you hear the longness of low damping factor....McIntosh amps ring in at 100 damping factor, and I heard two different Mac amps sound long and thick in the mids, compared to the K2 on the fronts....I heard the damping factor be 100 on the rears, against 3000 on the fronts....at the same time....all you have to do is shift your head toward one and then the other, and you soon don't want the long version 100, you want the cleaner one....higher damping factor was related to me by a few I trust as the amplified signal gets, "on and off the voice-coil more quickly".....the amplifier is more in control of the speaker element......

 

[Buckeyefan 1]

Mtry,

Where does Tom Nousaine and Ed Mullen stand on damping factor issues? They've contributed quite a bit to Secrets, which I'm surprised if it's such a voodoo issue. They're pretty well respected in the audio world.

 

[Buckeyefan 1]

.....I'll say this....a fair way to AB the damping factors of two amps is one pushing the rears, and the other pushing the fronts....it's best if all four speakers are the same, but mids is where you hear the longness of low damping factor....McIntosh amps ring in at 100 damping factor, and I heard two different Mac amps sound long and thick in the mids, compared to the K2 on the fronts....I heard the damping factor be 100 on the rears, against 3000 on the fronts....at the same time....all you have to do is shift your head toward one and then the other, and you soon don't want the long version 100, you want the cleaner one....higher damping factor was related to me by a few I trust as the amplified signal gets, "on and off the voice-coil more quickly".....the amplifier is more in control of the speaker element......

I don’t think that every scenario is covered here. The speaker-amplifier match hypothetically, could influence the sound. I would have to say that depending on the load, the amp could have a great deal of influence on the character of sound played from the speakers, based on this information. Has anyone seen anechoic response measurements of the same speakers with amplifiers with different dampening factors driving them? Has anyone done a paper on this? If so I'd be interested to see the actual quantifiable results.

 

[MacManNM]

.....I'll say this....a fair way to AB the damping factors of two amps is one pushing the rears, and the other pushing the fronts....it's best if all four speakers are the same, but mids is where you hear the longness of low damping factor....McIntosh amps ring in at 100 damping factor, and I heard two different Mac amps sound long and thick in the mids, compared to the K2 on the fronts....I heard the damping factor be 100 on the rears, against 3000 on the fronts....at the same time....all you have to do is shift your head toward one and then the other, and you soon don't want the long version 100, you want the cleaner one....higher damping factor was related to me by a few I trust as the amplified signal gets, "on and off the voice-coil more quickly".....the amplifier is more in control of the speaker element......

I concur. But, I believe it truly depends on the load (speakers). IE my XR 16's sound best when I drive them with my MC2105. Perhaps Roger Russell knew something we all didn’t.

EDIT: Roger KNOWS something. He is alive and kicking.

 

[WmAx]

I don’t think that every scenario is covered here. The speaker-amplifier match hypothetically, could influence the sound. I would have to say that depending on the load, the amp could have a great deal of influence on the character of sound played from the speakers, based on this information. Has anyone seen anechoic response measurements of the same speakers with amplifiers with different dampening factors driving them? Has anyone done a paper on this? If so I'd be interested to see the actual quantifiable results.

There is nothing mysterious.

Source Impedance = (Load Resistance * (Vunloaded - Vloaded)) / Vloaded

Knowing source impedance, you can calculate, exactly, the effect of a dynamic load or run an electrical simulation complete with response graphs if you have the target load impedance data available.

-Chris

 

[MacManNM]

There is nothing mysterious.

Source Impedance = (Load Resistance * (Vunloaded - Vloaded)) / Vloaded

Knowing source impedance, you can calculate, exactly, the effect of a dynamic load or run an electrical simulation complete with response graphs if you have the target load impedance data available.

-Chris

Would you mind quantifying those variables in a bit more detail?

IE:
Source Impedance = (Load Resistance * (Vunloaded - Vloaded)) / Vloaded

 

[WmAx]

Would you mind quantifying those variables in a bit more detail?

IE:
Source Impedance = (Load Resistance * (Vunloaded - Vloaded)) / Vloaded

Load Resistance = Known value dummy resistor
Vunloaded = voltage of amplifier with sine wave played with no load
Vloaded = voltage of amplifer with sine wave played with dummy resistor load

Example:

Dummy Load R = 8 Ohms
Unloaded V = 20 Volts
Loaded V = 19.25 Volts

(8*(20 - 19.25)) / 20 = 0.3 Ohms

-Chris

 

[MacManNM]

Load Resistance = Known value dummy resistor
Vunloaded = voltage of amplifier with sine wave played with no load
Vloaded = voltage of amplifer with sine wave played with dummy resistor load

Example:

Dummy Load R = 8 Ohms
Unloaded V = 20 Volts
Loaded V = 19.25 Volts

(8*(20 - 19.25)) / 20 = 0.3 Ohms

-Chris

So that is using a known load? So what about a reactive load instead of resistive?

 

[WmAx]

So that is using a known load? So what about a reactive load instead of resistive?

For the most part, the average mild capacitive/inductive loads generated by a typical loudspeaker will not have much effect on simulations using this calculated static source impedance value. To very accurately predict extreme reactive load conditions, however, you will have to also measure the amplifer voltage into varying controlled inductive/capacitive loads of known values to generate an additional set of data to account for this variable.

-Chris

 

[MacManNM]

For the most part, the average mild capacitive/inductive loads generated by a typical loudspeaker will not have much effect on simulations using this calculated static source impedance value. To very accurately predict extreme reactive load conditions, however, you will have to also measure the amplifer voltage into varying controlled inductive/capacitive loads of known values to generate an additional set of data to account for this variable.

-Chris

1st part, Bull crap. 2nd part true (well partially), but thats the whole point of this discussion. loudspeakers are a reactive load, threrefore the DF has bearing on their output.

 

[WmAx]

1st part, Bull crap.

The source impedance is the main factor determining the response of the amplifier into a dynamic load.

You will not find the inductive/capacitive reactive component as indicated by the electrical phase measurement of the speaker to have an appreciable effect on the response of the amplifer. And when it does have an effect, it will be primarily in the upper power limit ranges of the amplifier, not in the lower output ranges. Most speakers will not exeed about +/- 45 degrees electrical phase; speakers are designed to behave like this to operate properly with most amplifiers. Amplifiers are typically designed, in turn, to remain stabile and be driven properly into these mildly reactive load ranges. Reactive components become an issue when they are extreme(+/- 60-70 degrees electrical phase angle, for example) and forcing very high VA from the output transistors and putting excess demand(s) on the power supply than what was accounted for when designing the amplifier. If a speaker exceeds the typical nominal electrical phase angle range, it was probably not engineered very well(as how can it be considered good engineering to not consider critical parameters of compatibility with standard amplifier design parameters?).

-Chris

 

[MacManNM]

The source impedance is the main factor determining the response of the amplifier into a dynamic load.

You will not find the inductive/capacitive reactive component as indicated by the electrical phase measurement of the speaker to have an appreciable effect on the response of the amplifer. And when it does have an effect, it will be primarily in the upper power limit ranges of the amplifier, not in the lower output ranges. Most speakers will not exeed about +/- 45 degrees electrical phase; speakers are designed to behave like this to operate properly with most amplifiers. Amplifiers are typically designed, in turn, to remain stabile and be driven properly into these mildly reactive load ranges. Reactive components become an issue when they are extreme(+/- 60-70 degrees electrical phase angle, for example) and forcing very high VA from the output transistors and putting excess demand(s) on the power supply than what was accounted for when designing the amplifier. If a speaker exceeds the typical nominal electrical phase angle range, it was probably not engineered very well(as how can it be considered good engineering to not consider critical parameters of compatibility with standard amplifier design parameters?).

-Chris

This is all pretty much true with an amp that has a reasonable damping factor.

 

[Resident Loser]

I have an electric lawnmower...

The driver's mechanical movement(dampening) difference is because of the frequency response difference caused by the electrical reaction I described in my first post. When you change the frequency response curve(apply a peak in response for example), you affect the phase and amplitude of that response, which in turn dictates the time and frequency domain characteristics of that response. In fact, as I stated how you could force poor dampening factor behaviour(using a resistor) on a system that had good dampening factor behaviour, you can also force a poor dampening factor to sound like a high dampening factor system by using a parametric equalizer to apply (an) inverse correction curve(s) to counteract the initial curve(s). You can also force the high dampening factor system to behave like the poor dampening factor system via a parameteric equalizer.

-Chris

...in it's circuit there is some sort of electronic brake(in the guise of a small, potted network of sorts) to facilitate "immediate" stoppage of blade motion...as far as I know it has something to do with back-EMF stopping the armature's rotation...

Now I'm not trying to be difficult about this, only trying to understand what you have said previously. I can comprhend the equalization concept when dealing with pre-emphasis/de-emphasis or stating the RIAA playback curve in usec's rather than at specific frequencies, but I still fail to see how something more attuned to tonal balance using impedance feedback networks has anything to do with controlling cone motion. Maybe I'm just dumb.

With any sort of encode/decode "equalization" you are dealing with a known input and expect a specific output, whether it be for better S/N ratio as in FM or the ability to avoid over excursions of a cutter-head and still end up with a properly balanced frequency response from your vinyl.

Damping factor strikes me as a completely different animal, more akin to stopping my lawnmower blade. Music is different in that it's never "fixed"per se(as would be our inverse EQ curve)...Plucking a bass note(which one?) and bowing the same note, results in two different waveforms having the same nominal frequency but completely different rise and decay times.

Applying "equalization"(again as I understand term and have up until now have used it) would treat both the same way, although they are quite different. Our ficticious parametric equalizer still has a fixed frequency, amplitude and Q, not quite the ticket as far as I can see. Given the inherent randomness that is music, I still can't quite see damping as being an "equalization effect"...An amp with a lower output impedance and higher DF would simply seem to be more compliant(if that's the correct word) in it's ability to "react" and/or "control" the net effect of that back-EMF produced by the motor/generator effects of the load's voice-coil.

Can you (or anyone else) direct me to supporting documentation that will disabuse me of my current notions.

jimHJJ(...thanx...)