Damping
Yipes!!! I'm posting in the Solid State Forum.
Here are a few sources.
A thread from here and two online articles that I think at least bring up some good issues. I would love to hear anyone's informed take on (Frank, John ,....)the articles or Rodd's comment below about the amp absorbing and using the energy which implies that resistive dissapation of stored energy is not the sole electrical damping element (or at least I think it does).
Damping Factor, by Dick Pierce http://www.diyspeakers.net/Articles/Richard Pierce DAMPING FACTOR.pdf
Tomcik, D.J.; The Missing Link in Speaker Operation, Amplifier Damping and Speaker Performance. http://www.otlamp.com/articles/tomcik/index.html
and a local thread w/ some of our best and brightest:
I must admit I've been musing on Rodd's comment for a while that reads as follows:
Hey Guys,
"Damping Factor" is a way of putting a number on a very dynamic characteristic of an amplifier. The output impedance of an amp is not purely resistive. It is a complex function that has a phase angle and amplitude that varies from instant to instant. The inductive reactance of the drivers voice coil moving through the magnetic gap is also a complex function with phase and amplitude. Energy from the driver will be disipated in the the resistive component of this complex impedance, this is true. But, this is not the only way that the amp will damp the motion of the drivers cone. The amp will absorb and store energy from the driver and use it in the next instant of time depending on the phase and amplitude (which can be negative) relationship between the Rg and the back EMF of the driver.
Rodd Yamashita
The thread is here. Rodd's comment is page 3. http://www.diyaudio.com/forums/showthread.php?threadid=4536&perpage=15&pagenumber=1
Cheers:
Craig Ryder
Yipes!!! I'm posting in the Solid State Forum.
Here are a few sources.
A thread from here and two online articles that I think at least bring up some good issues. I would love to hear anyone's informed take on (Frank, John ,....)the articles or Rodd's comment below about the amp absorbing and using the energy which implies that resistive dissapation of stored energy is not the sole electrical damping element (or at least I think it does).
Damping Factor, by Dick Pierce http://www.diyspeakers.net/Articles/Richard Pierce DAMPING FACTOR.pdf
Tomcik, D.J.; The Missing Link in Speaker Operation, Amplifier Damping and Speaker Performance. http://www.otlamp.com/articles/tomcik/index.html
and a local thread w/ some of our best and brightest:
I must admit I've been musing on Rodd's comment for a while that reads as follows:
Hey Guys,
"Damping Factor" is a way of putting a number on a very dynamic characteristic of an amplifier. The output impedance of an amp is not purely resistive. It is a complex function that has a phase angle and amplitude that varies from instant to instant. The inductive reactance of the drivers voice coil moving through the magnetic gap is also a complex function with phase and amplitude. Energy from the driver will be disipated in the the resistive component of this complex impedance, this is true. But, this is not the only way that the amp will damp the motion of the drivers cone. The amp will absorb and store energy from the driver and use it in the next instant of time depending on the phase and amplitude (which can be negative) relationship between the Rg and the back EMF of the driver.
Rodd Yamashita
The thread is here. Rodd's comment is page 3. http://www.diyaudio.com/forums/showthread.php?threadid=4536&perpage=15&pagenumber=1
Cheers:
Craig Ryder
Low = 200 Thats silly.
Stardust Cowboys, Hmm sound like a band I heard at the Espy recently.
Where were they playing?
That must have been amusing, did Mrs Pass have the camera handy?
Just to add to the confusion, Has anyone considered power supply effects on damping factor.
ie between the postive and negative wire exists the amp and power supply. ie the more stored energy available the more power available to drive the speakers ultimately.
Just thinking out loud, if we assume the power supply is a reserve of stored energy, the amount of energy it can hold and maintain is governed the filter bank and level of the supply rails.
Thus higher rail voltage sq's the level of energy and has a great proportional impact on stored energy than adding filter capacitors.
Carver wrote a very intersting article on this subject when he was developing the Phase Linear 700, noted for its control and dynamics, the rails are nearly 100 volts +-, so the stored energy is massive. It also has many parrelled output devices and heeps of feedback, damping is quoted as 1000 to 1.
I while ago I used mine, a Clair Bros 700B to power front of house PA for a band in a pub, the amp they used previously was 150 watts.
The visually ability of the 700b to control the JBL 2226 15'' woofers in the J bins was surprise, the pk to pk excursion was probably 1.5 inches or more at very high velocity on the kick drum.
The punch was felt 2 blocks away! The speakers survived to live another day. The other amp sounded like someone hitting a pillow!
I am inclined to suggest its the power that moves the mountains and gives a subject account of high damping on the cones.
More confusion,
Bigger amps also have higher current output stage per say with many parrelled output devices, funny that they appear to have more control as seen by the above example (real fact)
Thus a piddly amp (say 30 watts) with high feedback could have so called high damping factor on paper, but appear to have less subjective control.
Ian
Stardust Cowboys, Hmm sound like a band I heard at the Espy recently.
Where were they playing?
That must have been amusing, did Mrs Pass have the camera handy?
Just to add to the confusion, Has anyone considered power supply effects on damping factor.
ie between the postive and negative wire exists the amp and power supply. ie the more stored energy available the more power available to drive the speakers ultimately.
Just thinking out loud, if we assume the power supply is a reserve of stored energy, the amount of energy it can hold and maintain is governed the filter bank and level of the supply rails.
Thus higher rail voltage sq's the level of energy and has a great proportional impact on stored energy than adding filter capacitors.
Carver wrote a very intersting article on this subject when he was developing the Phase Linear 700, noted for its control and dynamics, the rails are nearly 100 volts +-, so the stored energy is massive. It also has many parrelled output devices and heeps of feedback, damping is quoted as 1000 to 1.
I while ago I used mine, a Clair Bros 700B to power front of house PA for a band in a pub, the amp they used previously was 150 watts.
The visually ability of the 700b to control the JBL 2226 15'' woofers in the J bins was surprise, the pk to pk excursion was probably 1.5 inches or more at very high velocity on the kick drum.
The punch was felt 2 blocks away! The speakers survived to live another day. The other amp sounded like someone hitting a pillow!
I am inclined to suggest its the power that moves the mountains and gives a subject account of high damping on the cones.
More confusion,
Bigger amps also have higher current output stage per say with many parrelled output devices, funny that they appear to have more control as seen by the above example (real fact)
Thus a piddly amp (say 30 watts) with high feedback could have so called high damping factor on paper, but appear to have less subjective control.
Ian
It's an interesting observation that big amps without high
measured damping factors often control the bottom end
very well, and little amps often do not. This all being at
reasonable wattage levels that the small amp can handle
without distortion.
pass/ - listening to Jet Society to chill out
measured damping factors often control the bottom end
very well, and little amps often do not. This all being at
reasonable wattage levels that the small amp can handle
without distortion.
pass/ - listening to Jet Society to chill out
Thought you had gone to bed Mr Pass?
The time line makes it confusing ...
Hmm I think we are 19 hours ahead, so it is Monday afternoon and sorry is only 10.30 pm Monday night there, correct?
Ah well I just figured this from experience and observation.
But what is a high damping factor? At the tech college I did my speaker course they said anything over 30-50 was academic. (but we know musles and braun are the real reasons)
But I think it is more important to bass reflex systems, particularly high Q designs where the peak needs damping.
Putting the woofer in the feeback loop would be interesting hey, sorta motional feedback, pity I did not my on eof those Phillips MF speaker when they came out.
Ian
The time line makes it confusing ...
Hmm I think we are 19 hours ahead, so it is Monday afternoon and sorry is only 10.30 pm Monday night there, correct?
Ah well I just figured this from experience and observation.
But what is a high damping factor? At the tech college I did my speaker course they said anything over 30-50 was academic. (but we know musles and braun are the real reasons)
But I think it is more important to bass reflex systems, particularly high Q designs where the peak needs damping.
Putting the woofer in the feeback loop would be interesting hey, sorta motional feedback, pity I did not my on eof those Phillips MF speaker when they came out.
Ian
Hi,
Emerald? As above so below? Who knows.
Oh, damping factor. A myth. No, not a myth, a marketing myth. Or more precise a marketing lie. The change from an amplifier with a damping factor of 10000 to a damping factor of 10 will result in a minimal measurable and audible difference, if the damping factor is reduced by adding series resistance.
Moreover, by the technical design of moving coil loudspeakers having a high damping factor means to maximise distortion and compression. Of course, modern speakers do not take kindly to really low damping factors like 0.1 or 0.01, even if they result in reduced distortion and compression.
But then, they where never designed to sound good, but measure well in the frequency domain, to work in small reflex enclosures and to be manufacturable at very low prices. I guess people do get what they ask for.... (small, low, cheap)
Sayonara
emarald said:
Emerald? As above so below? Who knows.
Oh, damping factor. A myth. No, not a myth, a marketing myth. Or more precise a marketing lie. The change from an amplifier with a damping factor of 10000 to a damping factor of 10 will result in a minimal measurable and audible difference, if the damping factor is reduced by adding series resistance.
Moreover, by the technical design of moving coil loudspeakers having a high damping factor means to maximise distortion and compression. Of course, modern speakers do not take kindly to really low damping factors like 0.1 or 0.01, even if they result in reduced distortion and compression.
But then, they where never designed to sound good, but measure well in the frequency domain, to work in small reflex enclosures and to be manufacturable at very low prices. I guess people do get what they ask for.... (small, low, cheap)
Sayonara
Even though risking to get flamed I'd like to share my feelings (definitely subjective of course):
I think that more generously built amplifiers (big fat PSU, many paralleled output devices, high bias current) with reasonable feedback factors will show better control and bass precision than whimpy amps showing the same DF figures only due to the use of heavy feedback.
As long as the series resistance shows load- and frequency- independant behaviour one can live with quite low DF figures.
Even if the DF is decreasing with frequency it isn't tragic either as long as it isn't too extreme.
Regards
Charles
I think that more generously built amplifiers (big fat PSU, many paralleled output devices, high bias current) with reasonable feedback factors will show better control and bass precision than whimpy amps showing the same DF figures only due to the use of heavy feedback.
As long as the series resistance shows load- and frequency- independant behaviour one can live with quite low DF figures.
Even if the DF is decreasing with frequency it isn't tragic either as long as it isn't too extreme.
Regards
Charles
There is sometimes a presumption that something that sounds soft or not tightly controlled is caused by too low a damping factor, or more directly too high an output resistance of the amp.
This is logical. I'm sure if we put 10-ohm resistors in series with our speakers we would hear a softening effect, particularly in the bass.
But there are other reasons why something will sound soft or muddled that are nothing to do with output resistance. In my experience these other factors are usually dominant and this is why pursuing damping factors >>10 may not be worthwhile.
Nelson, why do you think the bigger-the-better? Do you have a specific reason for this or is it an observation?
This is logical. I'm sure if we put 10-ohm resistors in series with our speakers we would hear a softening effect, particularly in the bass.
But there are other reasons why something will sound soft or muddled that are nothing to do with output resistance. In my experience these other factors are usually dominant and this is why pursuing damping factors >>10 may not be worthwhile.
Nelson, why do you think the bigger-the-better? Do you have a specific reason for this or is it an observation?
phase_accurate said:"Even though risking to get flamed I'd like to share my feelings (definitely subjective of course):"
--------------------------------------------------------------------------------
Flaming for being subjective, should not be considered a danger here. I think that what drives us toward buillding and modifying audio gear, is music, the perception of which, is almost by definition, subjective.
I agree with phase accurate. Traderbam also, touches the issue of subjectivism from an other perspective. Two amplifiers do sound different, but this can be attributed to too many reasons.
Even in the proccess of being more objective, we start comparing two identical amps with the same load (speaker), but with one of them having each parameter that affects output resistance changed one at a time, who will confirm that the results will be objective? At first it has to be clarified what is the acoustically optimum against which we crosscheck. I am affraid that it is non existent. If electrical measurements were relating to acoustical opinions, it would be ok. But they are not, to a certain extend at least. And then as damping factor (D.F.) effects are concerned, an amplifier can not be seen in isolation. Cables, x-over, drive units, box, all are part of the chain. Can anyone define clearly the position of the amp output in this chain? I believe that defining it as the place where the output transistors are, is a compromise, serving the economy of the analysis certainly, but serving not the economy of the problem's solution.
I have built amps which if i will accept the proper D.F. definition, have D.Fs ranging from less than 1 to about 10000. Now, if i will tell you that with some particular speakers and some particular kind of music, i preffered the sound of the "less than one", how would you judge my words? (And how much different are they from the words of a "forrmal" proffessional review?)
But if i have to act positive and give a constructive (and not a chaotic) opinion, i would say that the D.F. issue is not at all different from the "voltage feed, or current feed " dilemma.
Regards
George
Thanks guys, appreciate the information, one more thing, is there a relationship betw the amp stability, ie 2ohm stable or 1ohm stable and dampening factor, aka would the dampening factor decrease the lower the resistence of the load ie 5000@4ohm, 500@2ohm and 50@1ohm, assuming a 2ohm stable amp, or am i barking up the wrong tree
damping
Well, since the damping factor is the ratio of load impedance to the amp output impedance, everytime you halve the load, you halve the damping factor.
This assumes that the output impedance is independent of the load impedance, which may not be 100% true, but to a first order, yes, the damping factor decreases with a decrease in load.
Jan Didden
Well, since the damping factor is the ratio of load impedance to the amp output impedance, everytime you halve the load, you halve the damping factor.
This assumes that the output impedance is independent of the load impedance, which may not be 100% true, but to a first order, yes, the damping factor decreases with a decrease in load.
Jan Didden
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