Damping Factor

[MLXXX]

53 minutes ago, Sime said:

Seeing as I’m not technically minded in all this, those videos that @MLXXX posted above showing speakers as generators, how does a speaker/amp system handle the energy being created by the speaker during playback (sorry if it’s already been explained)

Good question!  I'll be interested to read what others say in response. 

 

[acg]

3 hours ago, Sime said:

Seeing as I’m not technically minded in all this, those videos that @MLXXX posted above showing speakers as generators, how does a speaker/amp system handle the energy being created by the speaker during playback (sorry if it’s already been explained)

 

Well, as I understand it the back EMF is already incorporated into the impedance graph of the speaker...they are the resonant peaks that cause a higher SPL and are already part of the speaker Q...your speaker has probably already been designed to account for back EMF.

 

That said, an amp with a very low output impedance operates in voltage drive which means that the impedance peaks in a speaker make lower SPL than an amp with a higher output impedance.  In a commercial speaker that is designed to be run by a zero output impedance amplifier this is fine and you will hear what you are meant to hear.  It also makes designing the speaker somewhat easier in that you can use high mass cones which are harder to damp and therefore make more bass from a smaller box which is sort of defeating the purpose of the zero output impedance amplifier in the first place but it does allow for the modern aesthetic.  Perhaps I am a bit cynical,  but the way I see it zero output impedance amps are merely a way to make smaller speakers work.

 

If you really want to reduce back EMF you would use low excursion drivers with short voice coils and lightweight speaker cones.  Light cones are easy to damp and short voice coils produce less back EMF.  But the problem is size...those drivers need big boxes or even better they need horns because horns are the kings of low excursion.  That sort of system gets hard to fit in a room.

 

 

[Joe Rasmussen]

Maybe time to add a final chapter that illustrates the serious problem of specifying a number that implies that an amplifier can arrest most by adding damping. 

 

Here is a sobering graph:

 

 

How heat affects the resistance of the Voice Coil shows just have easy it become many times that of the output impedance of the amplifier. Above are relative resistance vs. temperature for Copper (blue), Aluminium (Red) and silver (Purple).

 

It can be readily seen that thermal resistance rises much higher than most amplifiers output impedace, making the DF number mute, especially with solid state amps. At even relatively average power, whereby the Voice Coil goes from 20C to 40C will add typically 1 Ohm to the amplifier's output impedance.

 

In more extreme cases, glues that hold the speaker together are rated 200C and higher and for good reason, hence the VC being above boiling point is not exactly a rare coincidence.

 

So when thermal resistance has made the VC rise from 20C to 40C, an amplifier with a fictitious DF of 1000 would now have less than 8 with 8 Ohm speakers and 4 with 4 Ohm speakers.

 

The DF number has now becomes meaningless, but then again it always was.''

 

Once again we see proof that the amplifier can only make damping less and even lesser.

 

The reason for the reduction in damping is very clear and it is down entirely to the alignment that has weakened because the Qes  and hence the total speaker system Q has been affected.

 

THERE IS NO OTHER EXPLANATION!

[Martykt]

On 16/10/2017 at 5:10 PM, Sime said:

Seeing as I’m not technically minded in all this, those videos that @MLXXX posted above showing speakers as generators, how does a speaker/amp system handle the energy being created by the speaker during playback (sorry if it’s already been explained)

What you are seeing in those videos (assuming those videos haven’t been “enhanced” for utube) is simply the transfer of energy.

With a speaker driver the energy supplied to the driver gets converted into kinetic energy (created by the magnetic field that is produced) and thermal energy (heat as Joe Rasmusen has just shown).

The speaker driver itself while being driven by an amplifier is not creating energy itself rather working as a transducer converting the energy supplied by the amplifier.

There may also be a small amount of Back EMF but this is probably better explained by @Joe Rasmussen though as a very simplistic way of looking at it is like when riding a bicycle up a hill it’s harder to pedal.

[PositivelyMusicallyGeared]

From a totally intuitive (no maths to prove anything) view, while speaker excursion is driven by the current going through the coil, would the control be manifested by a tiny voltage applied in the circuit?

 

This is a great discussion, from which I try to understand how things work. Thanks for everyone who's contributed.

[Joe Rasmussen]

53 minutes ago, PositivelyMusicallyGeared said:

From a totally intuitive (no maths to prove anything) view, while speaker excursion is driven by the current going through the coil, would the control be manifested by a tiny voltage applied in the circuit?

 

Not sure what you mean, but what is apparent is that a loudspeaker Voice Coil has a DC resistance. But it only measures that at DC (0Hz) and at all frequencies above DC, the impedance is higher than the DC resistance. That is the evidence that it is producing voltage.

 

That voltage, or force cannot be absorbed by the amplifier, because these forces oppose each other. Because the speaker is opposing, this causes less current to be drawn and hence this is reflected in the higher impedance. So if the impedance has doubled due to this effect, the current drawn from the amplifier. Even more, how do you think we measure the impedance? Simply measuring the current changing over frequency and then calculating the current and graphing it, and now you have an impedance plot.

 

So the more we understand this, the more ludicrous the subject of the amplifier exerting damping properties and that in fact the very opposite thing is happening.

 

Then we have another factor, the idea that the amplifier can short out effects from the speaker ignores something else. Yes, the amplifier will keep the voltage steady under load and should not change. But something does change. The current changes according to the load. This is fine and does not seem to be a problem, except for this biggie: The current phase angle changes. Not the voltage, the current changes and so does the current's electrical phase angle. What causes it? The speaker. So if the amplifier was a short, then how come that across that short, there is a varying current phase angle changing?

 

A short is a short. But this is not a short!

 

Beyond this point it gets into other related matters, such a Trevor mentioned earlier, that feedback can artificially lower the output impedance, but feedback can always (rarely) match the current delivery unless there is some real beef behind that output impedance, and now we come down to device's current capabilities and the power supply. A non-artificial output impedance can match current to go with it.

 

Trust me, I struggled to get a handle on this as well. But once you grasp the realities of what is going on, then things fall beautifully into place. When none other that Dr. Richard H. Small of Sydney University told me that the whole notion of amplifiers have some kind of ability to add damping, then I was insistent and he became very irritated. I didn't understand it yet, only later when I read the writings of Peter Schneider (I may have his spelling wrong) that made me understand how Thiele's and Small's parameters entirely defined the damping and alignment. It also became clear that I was completely wrong to challenge Small - but I am a lot wiser now.

 

But the amplifier DF notion will never die down? Who knows?

[A9X]

On 10/19/2017 at 7:17 PM, Joe Rasmussen said:

whereby the Voice Coil goes from 20C to 40C will add typically 1 Ohm to the amplifier's output impedance.

To the amplifier's LOAD not Zout.

[Addicted to music]

1 hour ago, A9X said:

To the amplifier's LOAD not Zout.

Hurray....someone is speaking my language.....

[MLXXX]

On 10/19/2017 at 6:17 PM, Joe Rasmussen said:

It can be readily seen that thermal resistance rises much higher than most amplifiers output impedace, making the DF number mute, especially with solid state amps. At even relatively average power, whereby the Voice Coil goes from 20C to 40C will add typically 1 Ohm to the amplifier's output impedance.

If driving a speaker hard, its voice coil resistance could indeed temporarily increase by 1 Ohm, and result in a temporary reduction in electrical damping. However that reduction in electrical damping is surely because of that very increase in the speaker's impedance, not because of any change in the amplifier's output impedance. In fact, the amplifier's output impedance (normally a quite low figure) should remain constant, unaffected by the temporary rise in temperature of the speaker voice coil.

 

I would suggest the following paragraph as a useful overview statement to assist people in gaining a perspective on Damping Factor:-

 

It is not so much the amplifier output impedance that is responsible for limited electrical damping of a speaker mounted in an enclosure. To a far greater extent it is the resistance of the speaker voice coil that limits electrical damping.

 

As far as audiophiles are concerned, the important idea to grasp that there is only so much an amplifier can do to foster electrical damping, was expressed tentatively by a Mr Langford Smith in 1947, as follows:

 

"If a loudspeaker can be represented by an equivalent circuit consisting of a resistance in series with an 'ideal' loudspeaker of 100 per cent efficiency, then the damping must be applied across the input terminals.

"In this case, even if the amplifier output resistance is zero, the damping is limited by the series resistance which, for 5 per cent efficiency, would be twenty times the resistance of the ideal loudspeaker. This extreme simplification, of course, leaves out the reactive components of the speaker impedance, but the argument still holds qualitatively.

"Can any reader of Wireless World point out any error in this argument? If it is true, there is very little gained by attempting to achieve excessively low output resistances."

 

Mr Langford Smith's argument was of course true. (He did not abandon the notion that an amplifier's output resistance is relevant for electrical damping of a loudspeaker but, but he did tentatively clarify that because the speaker's voice coil resistance is typically quite high of itself, it becomes unnecessary to pursue particularly low amplifier output resistance.)  Since the middle of the 20th century, the limitations in what an amplifier can do to foster electrical damping, because of typically high speaker voice coil resistance, would have been generally understood by those with relevant technical expertise. And textbooks have reflected that understanding.

 

 

On 10/19/2017 at 10:22 PM, Joe Rasmussen said:

But the amplifier DF notion will never die down? Who knows?

I think that as long as audiophiles understand that electrical damping is primarily limited by speaker coil impedance and that there is no point in chasing extremely high DF numbers through extremely low amplifier output impedance, that is a sufficient understanding for audiophiles. 

 

The significance of amplifier damping factor will inevitably be misunderstood by some audiophiles. I suspect it would generally not be misunderstood by those with a technical background in electronics: if such people had any doubts they could quickly read about amplifier DF using a reference source.

 

Anyone with internet access can read the helpful explanation that currently appears on Wikipedia at https://en.wikipedia.org/wiki/Damping_factor

[Addicted to music]

 

36 minutes ago, MLXXX said:

If driving a speaker hard, its voice coil resistance could indeed temporarily increase by 1 Ohm, and result in a temporary reduction in electrical damping. However that reduction in electrical damping is surely because of that very increase in the speaker's impedance, not because of any change in the amplifier's output impedance. In fact, the amplifier's output impedance (normally a quite low figure) should remain constant, unaffected by the temporary rise in temperature of the speaker voice coil.

 

I would suggest the following paragraph as a useful overview statement to assist people in gaining a perspective on Damping Factor:-

 

It is not so much the amplifier output impedance that is responsible for limited electrical damping of a speaker mounted in an enclosure. To a far greater extent it is the resistance of the speaker voice coil that limits electrical damping.

 

As far as audiophiles are concerned, the important idea to grasp that there is only so much an amplifier can do to foster electrical damping, was expressed tentatively by a Mr Langford Smith in 1947, as follows:

 

"If a loudspeaker can be represented by an equivalent circuit consisting of a resistance in series with an 'ideal' loudspeaker of 100 per cent efficiency, then the damping must be applied across the input terminals.

"In this case, even if the amplifier output resistance is zero, the damping is limited by the series resistance which, for 5 per cent efficiency, would be twenty times the resistance of the ideal loudspeaker. This extreme simplification, of course, leaves out the reactive components of the speaker impedance, but the argument still holds qualitatively.

"Can any reader of Wireless World point out any error in this argument? If it is true, there is very little gained by attempting to achieve excessively low output resistances."

 

Mr Langford Smith's argument was of course true. (He did not abandon the notion that an amplifier's output resistance is relevant for electrical damping of a loudspeaker but, but he did tentatively clarify that because the speaker's voice coil resistance is typically quite high of itself, it becomes unnecessary to pursue particularly low amplifier output resistance.)  Since the middle of the 20th century, the limitations in what an amplifier can do to foster electrical damping, because of typically high speaker voice coil resistance, would have been generally understood by those with relevant technical expertise. And textbooks have reflected that understanding.

 

 

I think that as long as audiophiles understand that electrical damping is primarily limited by speaker coil impedance and that there is no point in chasing extremely high DF numbers through extremely low amplifier output impedance, that is a sufficient understanding for audiophiles. 

 

The significance of amplifier damping factor will inevitably be misunderstood by some audiophiles. I suspect it would generally not be misunderstood by those with a technical background in electronics: if such people had any doubts they could quickly read about amplifier DF using a reference source.

 

Anyone with internet access can read the helpful explanation that currently appears on Wikipedia at https://en.wikipedia.org/wiki/Damping_factor

The paragraph that explains it so well:

 

Speaker diaphragms have mass, and their surroundings have stiffness. Together, these form a resonant system, and the mechanical cone resonance may be excited by electrical signals (e.g., pulses) at audio frequencies. But a driver with a voice coil is also a current generator, since it has a coil attached to the cone and suspension, and that coil is immersed in a magnetic field. For every motion the coil makes, it will generate a current that will be seen by any electrically attached equipment, such as an amplifier. In fact, the amp's output circuitry will be the main electrical load on the "voice coil current generator". If that load has low resistance, the current will be larger and the voice coil will be more strongly forced to decelerate. A high damping factor (which requires low output impedance at the amplifier output) very rapidly damps unwanted cone movements induced by the mechanical resonance of the speaker, acting as the equivalent of a "brake" on the voice coil motion (just as a short circuit across the terminals of a rotary electrical generator will make it very hard to turn). It is generally (though not universally) thought that tighter control of voice coil motion is desirable, as it is believed to contribute to better-quality sound.

 

 

Edited:  remember how I talked about the difference when you push the speaker diaphragm and there's a difference between the amp off and on.....

you guys should try it.   

 

Notice also it separately defines the amplifier output and load impedance are not the same.

Edited October 21, 2017 by Addicted to music

[MLXXX]

1 minute ago, Addicted to music said:

The paragraph that explains it so well:

I agree. That paragraph in Wikipedia is quite readable and helpful (and as far as I can tell, it is accurate technically!).

[Addicted to music]

5 minutes ago, MLXXX said:

I agree. That paragraph in Wikipedia is quite readable and helpful (and as far as I can tell, it is accurate technically!).

And this saids it all so the OP @Sime  can understand what I've been saying all along.

 

A high damping factor (which requires low output impedance at the amplifier output) very rapidly damps unwanted cone movements induced by the mechanical resonance of the speaker, acting as the equivalent of a "brake" on the voice coil motion (just as a short circuit across the terminals of a rotary electrical generator will make it very hard to turn). It is generally (though not universally) thought that tighter control of voice coil motion is desirable, as it is believed to contribute to better-quality sound.

 

Technically it's 100% bang on.

Edited October 21, 2017 by Addicted to music

[Joe Rasmussen]

On 21/10/2017 at 10:07 AM, A9X said:

To the amplifier's LOAD not Zout.

Since the amplifier can only see a single value at any discrete frequency, they are one and the same.

 

Pick a frequency and the amplifier sees the 'load' and it is only a single number.

 

So in our case, if the sum resistance has been increased by thermal means by one Ohm (and that will be added flat across all frequencies), then it wouldn't know what caused it and where in the sum series of those elements of resistance of the speaker wire, the LF coil in the crossover, the nominal 20C DC resistance of the voice coil, which now has gone up an extra Ohm, it is all the same.

 

Once again, we assume the low output impedance of the amplifier is some kind of return 'short' because it has a low value, in some cases vanishingly low (with the use of a lot of feedback to give it that enhanced effect/number).

 

The fact is that the amplifier cannot absorb any back-EMF from the load, the forces oppose each other and causes less current to be drawn and hence the result is the the impedance gets pushed above the DC resistance of the voice coil. Nothing gets absorbed by the amplifier, despite its low output impedance. 

[Joe Rasmussen]

On 21/10/2017 at 12:18 PM, Addicted to music said:

 

A high damping factor (which requires low output impedance at the amplifier output) very rapidly damps unwanted cone movements induced by the mechanical resonance of the speaker, acting as the equivalent of a "brake" on the voice coil motion (just as a short circuit across the terminals of a rotary electrical generator will make it very hard to turn). It is generally (though not universally) thought that tighter control of voice coil motion is desirable, as it is believed to contribute to better-quality sound.

 

Technically it's 100% bang on.

 

No, it is completely wrong, from so many angles. It was wrong in 1975 when Richard Small, a far better source than any webpage, brought it to my attention, that the above explanation violates the central theme of Thiele-Small Parameters, that it is the alignment of a loudspeaker system that determines the damping.

 

Secondly, the above explanation implies that back-EMF produced by the driver is some kind of over-shoot. Nothing could be further from the truth. Motional back-EMF is produced when the coil moves in the magnetic gap. It does so, because it moves and makes sound.

 

Clearly this is not an over-shoot, because the back-EMF happens all the time. And that back-EMF cannot be absorbed by the amplifier. If it could, it would not result in a brake of an over-shoot, it would create a speaker with no sound!

 

This has to be the most amazing and incorrect theory, that has had a longevity that seems un-ending. It is the mother of all incorrect audio myths.

 

No sign of it going away (talk about fake news not being news or 'new' at all).

[Joe Rasmussen]

Hi all, the last two posts from less than sunny Copenhagen, arrived yesterday. Two weeks from now will be going to a certain Triode Festival 2017. Looking forward to seeing some interesting people there (some you read about) and chewing the fat. Suspect this topic might come up or might bring it up for fun, so this discussion here has refreshed my mind and thank you for that.

 

I rarely think of this topic, this may surprise some here - but its always interesting when it gets back up and never ceases to amaze me.

[Zaphod Beeblebrox]

6 minutes ago, Joe Rasmussen said:

 

 

This has to be the most amazing and incorrect theory, that has had a longevity that seems un-ending. It is the mother of all incorrect audio myths.

 

Oh there are many more persistent, nonsensical myths than that. The output impedance of an amplifier must be adequately low, such that it will work with the vast majority of loudspeakers. Therefore, in that sense, so-called 'Damping Factor' is important. It is not necessarily important for the reasons commonly claimed, nor does the DF need to be spectacularly high. An equivalent DF of around 150 will deal with the most brutal loudspeaker loads (ESLs, for instance).

 

In reality, output impedance DOES matter. Dressing it up as Damping Factor is wrong.

 

I would argue that the most persistent, nonsensical myths are these:

 

* Valves = good, SS = bad.

* SS = good, valves = bad.

* So-called PRAT.

* All those silly little accessories that cannot provide any measurable improvement.

* Fancy (and expensive) fuses.

* Fancy (and expensive) power leads.

* Etc. 

[Joe Rasmussen]

2 minutes ago, Zaphod Beeblebrox said:

 

In reality, output impedance DOES matter. Dressing it up as Damping Factor is wrong.

 

 

Hi Trevor, absolutely right. Dressing it up like that implies magical qualities to an amplifier, when we know the any added impedance from anywhere, does not improve damping, but lessens it. 

[Martykt]

15 minutes ago, Joe Rasmussen said:

Hi all, the last two posts from less than sunny Copenhagen, arrived yesterday. Two weeks from now will be going to a certain Triode Festival 2017. Looking forward to seeing some interesting people there (some you read about) and chewing the fat. Suspect this topic might come up or might bring it up for fun, so this discussion here has refreshed my mind and thank you for that.

 

I rarely think of this topic, this may surprise some here - but its always interesting when it gets back up and never ceases to amaze me.

Triode Festival sounds like fun !!  

 

Make sure you take lots of photos for us poor sods stuck here back in Oz !!  

[A9X]

45 minutes ago, Joe Rasmussen said:

Since the amplifier can only see a single value at any discrete frequency, they are one and the same.

No they're not. Back it up with proof from an EE text. Not audiophile waffle, or something someone told you, but from a real EE source.

45 minutes ago, Joe Rasmussen said:

 

The fact is that the amplifier cannot absorb any back-EMF from the load, the forces oppose each other and causes less current to be drawn and hence the result is the the impedance gets pushed above the DC resistance of the voice coil. Nothing gets absorbed by the amplifier, despite its low output impedance. 

You don't need to lecture me; I never said anything of the sort.

[acg]

1 hour ago, Joe Rasmussen said:

Hi all, the last two posts from less than sunny Copenhagen, arrived yesterday. Two weeks from now will be going to a certain Triode Festival 2017. Looking forward to seeing some interesting people there (some you read about) and chewing the fat. Suspect this topic might come up or might bring it up for fun, so this discussion here has refreshed my mind and thank you for that.

 

Awesome!  Invite only...it's not like you can just rock up to the door and expect to get in.  Have fun, and like others have said, photos or it never happened.

[davewantsmoore]

Quote

For every motion the coil makes, it will generate a current that will be seen by any electrically attached equipment, such as an amplifier. In fact, the amp's output circuitry will be the main electrical load on the "voice coil current generator". If that load has low resistance, the current will be larger and the voice coil will be more strongly forced to decelerate. A high damping factor (which requires low output impedance at the amplifier output) very rapidly damps unwanted cone movements induced by the mechanical resonance of the speaker, acting as the equivalent of a "brake" on the voice coil motion (just as a short circuit across the terminals of a rotary electrical generator will make it very hard to turn). It is generally (though not universally) thought that tighter control of voice coil motion is desirable, as it is believed to contribute to better-quality sound.

 

To me this is the heart of the matter..... and most of what's being discussed otherwise is somewhat semantics.

 

The idea is that these cone movements are "unwanted" ... and we need to use a low output impedance to stop them.    Where is the evidence of that?    The only detailed investigations I have seen of this, demonstrate it to be hardly a universal truth ... if not just plain wrong.

 

Increased excursion at the system resonance (or elsewhere the speaker impedance rises) ... is just a different frequency response.... which can be corrected in the speaker crossover/filter.

 

Once we realise this, we are free to examine the best arrangement for the amplifier/speaker system (independent of the frequency response, "unwanted movement" furfie).

 

 

.... give me a high(er) output impedance amplifier any day  (assuming the amplifier has acceptable non-linear distortion, and power output)

 

..... lowering the output impedance is senseless.

[Addicted to music]

22 minutes ago, davewantsmoore said:

 

To me this is the heart of the matter..... and most of what's being discussed otherwise is somewhat semantics.

 

The idea is that these cone movements are "unwanted" ... and we need to use a low output impedance to stop them.    Where is the evidence of that?    The only detailed investigations I have seen of this, demonstrate it to be hardly a universal truth ... if not just plain wrong.

 

Increased excursion at the system resonance (or elsewhere the speaker impedance rises) ... is just a different frequency response.... which can be corrected in the speaker crossover/filter.

 

Once we realise 

 

..... lowering the output impedance is senseless.

I wonder how many bottles you have had to type that last statement.  

 

Then stick with valve amps and ...You can have an amplifier with as higher output impedance as you wish while I go the other way.  

What a statement that last sentence is, it's just defies all the things that relates to ohms law and component selection:

 

im very sure that as a battery (any type)  exhaust it's energy the internal (output impedance) rises.

im sure when select component for capacitors that you look for the lowest ESR (effective series resistance) Notice I defined that in brackets! 

When you select output bjt devices to drive speakers, I'm sure every SS amp designer will select a devices with the lowest output impedance.  Keeping the output impedance low on drive devices enable you to switch that device on so little energy is absorbed and it gets tranferred to the load....

 

But hell what what I know, coming from someone who knows crap about the nbn co worked on printers and have been thinking like a gynocolgist this evening....

 

 

 

[Zaphod Beeblebrox]

6 hours ago, davewantsmoore said:

 

..... lowering the output impedance is senseless.

Here are three graphs indicating the ramifications of low, medium and high output impedance figures of three different amplifiers.

 

The first graph is of a zero global NFB valve amp (high output impedance).

The second graph is of a low global NFB valve amp (medium output impedance).

The third graph is of a low global NFB SS amp (low-ish output impedance).

Note the large differences in frequency response, when driving identical simulated speaker loads. It is abundantly clear that amp #1 will be audibly inaccurate. Amp #2 will be audibly inaccurate to critical listeners and amp #3 will likely be very difficult for even critical listeners to fault. 

 

So, no, lowering output impedance is, generally, a desirable thing, when using most loudspeakers. Amplifier #3 presents an output impedance of approximately 0.1 Ohms, so much below that figure is pretty much academic, unless, of course, the load impedance is more brutal than Sterophile's simulated speaker load (which most certainly can occur). 

Edited October 25, 2017 by Zaphod Beeblebrox

[davewantsmoore]

4 hours ago, Zaphod Beeblebrox said:

Here are three graphs indicating the ramifications

Sorry, I should be clear, and mentioned (like I've said a number of times this thread) ..... that changing the output impedance may result in a difference frequency response.

 

With lots of speakers, that "may" ... becomes "almost certainly" .... and this frequency response might be bad or good .... but probably bad if the designer didn't expect it.

 

 

But this is all a red herring, for the general question of high/low damping factor yah? nah?.

 

It would be like asking which type of engine fuel is superior (in general) A or B ? .....   and answering by saying, that because my car isn't designed to accept B, then A must be superior.     Well, no - it's just A is more suited.   It might be that B is fantastic, and we should redesign everything to accept B.

 

 

So like I've said a number of times..... The output Z of an amp, may/will make the FR of the speaker change.    This could be drastic .... and you should use what amplifier the speaker manufacturer recommends.

 

 

.... but if you want understand whether high or low damping factor is generally "superior"..... we need to look past that frequency response change.

 

Quote

So, no, lowering output impedance is, generally, a desirable thing, when using most loudspeakers.

 

Let's be very clear and add.....   BECAUSE those speakers are designed to expect a low output impedance.

 

It is nothing to do with the "general superiority" of low output impedance (or "high damping factor") .... like we are told ad nauseam.

 

When we design speakers with identical frequency responses  (but employ different "electrical damping") ..... it is (can be) a very different story - and the true nature of damping factor (or lack of it) is revealed.

[davewantsmoore]

5 hours ago, Zaphod Beeblebrox said:

simulated speaker loads.

Sure.   This is a simulated small 2way speaker....   and you wouldn't want to increase the amplifier output impedance for this speaker, as it's impedance swings too much.

 

That doesn't tell us that "low output Z"  is generally good or bad ..... just that it's not good for this speaker.