Anyone dispute this ?
Damping Factor =Zload/Zamp
Zload = speaker impedance
Zamp = output impedance of amplifier
Is the output impedance of the class ab amplifier a
constant, ie restistive measure or is
there any AC components which would
cause the output impedance to be a variable?
On a typical class ab amplifier, if you were
to trace the path that contribute to output impedance,
what components are those? ie, speaker terminal --> output
coil --> output stage transistor w/associated series resistor + what else?
Damping Factor =Zload/Zamp
Zload = speaker impedance
Zamp = output impedance of amplifier
Is the output impedance of the class ab amplifier a
constant, ie restistive measure or is
there any AC components which would
cause the output impedance to be a variable?
On a typical class ab amplifier, if you were
to trace the path that contribute to output impedance,
what components are those? ie, speaker terminal --> output
coil --> output stage transistor w/associated series resistor + what else?
Damping factor is defined into a load of 8 ohms.
Output impedance is reactive as well as resistive. There is usually a coil, and in SS almost always emitter resistors, and the dominant pole reflects back into it as well via NFB.
Output impedance is reactive as well as resistive. There is usually a coil, and in SS almost always emitter resistors, and the dominant pole reflects back into it as well via NFB.
A solid-state amplifier's output impedance typically rises with frequency due to less available negative feedback. The output impedance appears inductive.
The "gyrator" uses this principle to make capacitors work like inductors.
Ed
The "gyrator" uses this principle to make capacitors work like inductors.
Ed
The voltage (current) generated by the coil goes through the DC resistance Re, of the driver first. While not in the amplifier, this mainly defines the maximum attainable damping factor.
@ostripper
https://benchmarkmedia.com/blogs/application_notes/audio-myth-damping-factor-isnt-much-of-a-factor
That website, regardless of its content, looks like a sales pitch for Benchmark amps and fancy cables.
https://benchmarkmedia.com/blogs/application_notes/audio-myth-damping-factor-isnt-much-of-a-factor
That website, regardless of its content, looks like a sales pitch for Benchmark amps and fancy cables.
While I agree with the article, the damping factor is well described and it shifts the focus to a better understanding of the subject: the frequency response.
Do understand the actual damping factor isn't addressed, but the response is, this is a valid, but different matter.
I agree with wiseoldtech, because while they boast about the fact that there is an assumption, they are missing a very important key factor, which is that these amps (as well as most of the people here), will use the amp and its calculations on a passive filtered speaker.
The Rdc of that induction to filter will usually be equal to or bigger than the Rdc of the total cable used.
Do the math again with an induction for a 3-way of about 3 to 5 mH and see what happens..
Iow. The article is only valid for active speakers (subwoofers?) and even then, Re dictates the damping factor.
Do understand the actual damping factor isn't addressed, but the response is, this is a valid, but different matter.
I agree with wiseoldtech, because while they boast about the fact that there is an assumption, they are missing a very important key factor, which is that these amps (as well as most of the people here), will use the amp and its calculations on a passive filtered speaker.
The Rdc of that induction to filter will usually be equal to or bigger than the Rdc of the total cable used.
Do the math again with an induction for a 3-way of about 3 to 5 mH and see what happens..
Iow. The article is only valid for active speakers (subwoofers?) and even then, Re dictates the damping factor.
To put things in relatively simple terms..
Damping factor varies from amp design, to amp design, that's obvious.
The higher the damping factor is, the more "tightness" and control over the speakers that are attached to it.
In other words, a low damping factor allows a more sloppy control, and some people like that.
Bass frequencies in particular, are bloated, boomy, letting the speaker do its own thing.
Controlling a woofer cone from within an amp, using a high level of damping, brings a tightness to bass.
Of course, like mterbekke mentioned, a lot depends on the speaker's design too.
Damping factor varies from amp design, to amp design, that's obvious.
The higher the damping factor is, the more "tightness" and control over the speakers that are attached to it.
In other words, a low damping factor allows a more sloppy control, and some people like that.
Bass frequencies in particular, are bloated, boomy, letting the speaker do its own thing.
Controlling a woofer cone from within an amp, using a high level of damping, brings a tightness to bass.
Of course, like mterbekke mentioned, a lot depends on the speaker's design too.
Fat cables will at least bring the OPS's damping factor right to the speaker terminals. cables don't have to be "fancy".
I agree , but screw them... our DIYA "wolverine" with 8 sanken MT-200's easily beats their 3200$ fancy amp.
The cable that goes across the spider on most woofers would cripple any high damping factor. Best I've seen is a weaved (in the spider)
quad 12 gauge voice coil lead on a 1KW car audio driver.
I use cheap 10ga car audio wire in my subs , even as it is only 1/2 meter.
@ostripper
"cable that goes across the spider on most woofers would cripple any high damping factor."
Without wanting to get into any "wire" discussions, lord knows they've been pounded to death already, it's interesting to note that the use of fuses is often ignored.
Ok, so some guys like 12, 10 gauge wires to hook up their speakers. - I personally use common copper 16 gauge zip cord and don't have an issue with it.
On average, speaker cables will have to pass less than 25 volts, at maybe 1/2 to 1 amp or so, often less at normal listening levels.
Now, consumer level domestic use amps, built with B+ safety fuses, sometimes use values of maybe 6.3 amp fuses at the line cord, and perhaps less for speaker protection.
That thin, almost hard to see thin fusible alloy wire inside the fuse is certainly smaller than a 10 gauge wire.
Would stuffy, fussy audiophiles consider that a weak spot? - like a "bottleneck" in the flow of music to your ears?
Does anybody realize the relation of AC voltage and current (think Ohms Laws) feeding a voice coil with its inductance is highly overblown to worry about?
This all reminds me of the decades-ago Wattage Wars of consumer amps and receivers - which in reality was a marketing trend intended to boost revenue for manufacturers, and convince the consumer that "more is better".
No different than high-powered automobiles, sports cars, etc., all designed to feed the gullible minds at their expense.
Mind you, I can appreciate having adequate "power" available to enjoy listening to music at home, but where does it all start to become an obsession based on the hype instilled on the public?
I once saw somebody wire a phono cartridge in a typical removable tonearm headshell with 14 gauge Romex, claiming that it allowed a better "flow" of the music.
Imagine that!... a mere 2 inch length of solid Romex from the cartridge pins to the headshell!
Nuts!
"cable that goes across the spider on most woofers would cripple any high damping factor."
Without wanting to get into any "wire" discussions, lord knows they've been pounded to death already, it's interesting to note that the use of fuses is often ignored.
Ok, so some guys like 12, 10 gauge wires to hook up their speakers. - I personally use common copper 16 gauge zip cord and don't have an issue with it.
On average, speaker cables will have to pass less than 25 volts, at maybe 1/2 to 1 amp or so, often less at normal listening levels.
Now, consumer level domestic use amps, built with B+ safety fuses, sometimes use values of maybe 6.3 amp fuses at the line cord, and perhaps less for speaker protection.
That thin, almost hard to see thin fusible alloy wire inside the fuse is certainly smaller than a 10 gauge wire.
Would stuffy, fussy audiophiles consider that a weak spot? - like a "bottleneck" in the flow of music to your ears?
Does anybody realize the relation of AC voltage and current (think Ohms Laws) feeding a voice coil with its inductance is highly overblown to worry about?
This all reminds me of the decades-ago Wattage Wars of consumer amps and receivers - which in reality was a marketing trend intended to boost revenue for manufacturers, and convince the consumer that "more is better".
No different than high-powered automobiles, sports cars, etc., all designed to feed the gullible minds at their expense.
Mind you, I can appreciate having adequate "power" available to enjoy listening to music at home, but where does it all start to become an obsession based on the hype instilled on the public?
I once saw somebody wire a phono cartridge in a typical removable tonearm headshell with 14 gauge Romex, claiming that it allowed a better "flow" of the music.
Imagine that!... a mere 2 inch length of solid Romex from the cartridge pins to the headshell!
Nuts!
The real problem with output impedances greater than a few tenths of an ohm is that they noticeably shift the speaker's crossover points. Usually the overlap between drivers is increased. That may sound subjectively "better", but the speaker is not performing as designed.
Ed
Ed
I think the benefits of a high damping factor cannot be fully realized if the speaker system contains a passive crossover.
The objective of high damping factor is more accurate control of the driver cone and hence lower distortion, which is a result of the amps low internal impedance absorbing the back emf generated by driver as it moves.
A passive crossover is a complex network of reactive components and resistors which lies between the drivers and the amp.
Therefore the drivers never really see the amps low impedance, especially in the crossover regions, so they receive little or no benefit from it.
The solution is to eliminate the passive crossover and use an active crossover ahead of the amp.
Drivers are now connected directly to the amp and the high damping factor actually does something.
Speaker distortion is the big elephant in the room compared to the low distortion of modern electronics, so it makes sense to minimize it.
I've built two active systems like this now and I'm constantly impressed by their clarity and detail.
No more passives for me.
The objective of high damping factor is more accurate control of the driver cone and hence lower distortion, which is a result of the amps low internal impedance absorbing the back emf generated by driver as it moves.
A passive crossover is a complex network of reactive components and resistors which lies between the drivers and the amp.
Therefore the drivers never really see the amps low impedance, especially in the crossover regions, so they receive little or no benefit from it.
The solution is to eliminate the passive crossover and use an active crossover ahead of the amp.
Drivers are now connected directly to the amp and the high damping factor actually does something.
Speaker distortion is the big elephant in the room compared to the low distortion of modern electronics, so it makes sense to minimize it.
I've built two active systems like this now and I'm constantly impressed by their clarity and detail.
No more passives for me.
A key consideration is synergy.
Speakers and amplifiers should always be auditioned in combination.
For example, a speaker that sounds good with a solid-state amplifier may not sound so good with a valve amplifier and vice versa.
Damping factor was a term invented by Friz Langford-Smith in the Radiotron Designer's Handbook in around 1946.
He then retracted this pretty much entirely is Wireless World August 1948, page 309. He recognized that an amplifier has no real effect in damping a loudspeaker's behavior, because the voice coil resistance and reflected air impedance vastly dominate. Provided that an amplifier output impedance is low enough so that it does not impact on the loudspeaker frequency response, that is good enough. A valved/tubed amplifier with a typical output impedance of 0.5 ohm is clearly good enough. Going for extreme "damping factor" as being a good thing is just a specmanship argument, with the controversy being perpetuated by amplifier manufacturers.
That as techtool is also modified by any crossover that is in the way, with typical resistors of several ohms to tens of ohms being used, plus reactive components.
He then retracted this pretty much entirely is Wireless World August 1948, page 309. He recognized that an amplifier has no real effect in damping a loudspeaker's behavior, because the voice coil resistance and reflected air impedance vastly dominate. Provided that an amplifier output impedance is low enough so that it does not impact on the loudspeaker frequency response, that is good enough. A valved/tubed amplifier with a typical output impedance of 0.5 ohm is clearly good enough. Going for extreme "damping factor" as being a good thing is just a specmanship argument, with the controversy being perpetuated by amplifier manufacturers.
That as techtool is also modified by any crossover that is in the way, with typical resistors of several ohms to tens of ohms being used, plus reactive components.
sawyers... I could not say it better.
In fact we can argue if it is even beneficial to have a resistor on the output of the amplifier to increase source impedance.
Some type of distortion is reduced doing so. Thats for sure.
An extra cap creating a RC filter could help minimizing rf to reach the input stage, but still keeping the bandwidth of the feedback loop big enough.
Transconductance amplifiers with 400ohm in output resistance reduces distortion. There is a lot to read about this here.
In fact we can argue if it is even beneficial to have a resistor on the output of the amplifier to increase source impedance.
Some type of distortion is reduced doing so. Thats for sure.
An extra cap creating a RC filter could help minimizing rf to reach the input stage, but still keeping the bandwidth of the feedback loop big enough.
Transconductance amplifiers with 400ohm in output resistance reduces distortion. There is a lot to read about this here.
The power supply has a lot to do with the damping factor also.
Tight B+, along with a power transformer with good regulation, minimizes sag, and any impedence issues at the business end of an amp, and naturally well-designed feedback helps.
Speaker and amplifier impedances are MOSTLY AC components, and, amplitude dependent because they are not perfectly linear. These reactive components are mostly a reflection of the mechanical behavior of the diaphragm etc. Looking at a speaker impedance graph: The rated impedance is usually about 120% of the DC resistance, which is the value at the valley of a speaker impedance graph.
Amplifier impedance is a function of the output circuit and the feedback around that stage. An emitter follower output starts with a relative low impedance and is further improved by feedback, which is much more effective at low frequencies where the loop gain is highest. The high plate impedance of tube amps can be lowered with some feedback but not much before the feedback becomes unstable. The output transformer exasperates the problem with massive reactance and resonance issues, so tube amps often take feedback from the primary instead of from the transformer secondary.
However, the value of a low output impedance is not a complete consensus. Some people think a "current" output, ie high impedance output reduces the speaker distortion. Certainly, it creates problems with a predictable voltage and clipping. Current wisdom is that the ideal impedance depends on the driver type and range. An electromotive (voice coil) woofer generally performs best with a large damping factor, but other drivers have "series" resonances which are best controlled with a high impedance drive. The classic solution is to wire the woofer directly to the amplifier, with only perhaps a series inductor, and build out the amplifier impedance with an attenuator to the mid and tweeter. Piezo tweeters are current driven and work best from a Hi-Z source, which may be just a small series capacitor. Any given driver has both series and parallel resonances, so the best compromise is neither current (high impedance) or low impedance (~0), but something similar to the driver impedance. This is reminiscent to the "Impedance match" concept, but for different reasons.
Amplifier impedance is a function of the output circuit and the feedback around that stage. An emitter follower output starts with a relative low impedance and is further improved by feedback, which is much more effective at low frequencies where the loop gain is highest. The high plate impedance of tube amps can be lowered with some feedback but not much before the feedback becomes unstable. The output transformer exasperates the problem with massive reactance and resonance issues, so tube amps often take feedback from the primary instead of from the transformer secondary.
However, the value of a low output impedance is not a complete consensus. Some people think a "current" output, ie high impedance output reduces the speaker distortion. Certainly, it creates problems with a predictable voltage and clipping. Current wisdom is that the ideal impedance depends on the driver type and range. An electromotive (voice coil) woofer generally performs best with a large damping factor, but other drivers have "series" resonances which are best controlled with a high impedance drive. The classic solution is to wire the woofer directly to the amplifier, with only perhaps a series inductor, and build out the amplifier impedance with an attenuator to the mid and tweeter. Piezo tweeters are current driven and work best from a Hi-Z source, which may be just a small series capacitor. Any given driver has both series and parallel resonances, so the best compromise is neither current (high impedance) or low impedance (~0), but something similar to the driver impedance. This is reminiscent to the "Impedance match" concept, but for different reasons.
I've just opened up some old Heybrooks, they've certainly cut costs with the internal wire...
It's unlikely any fat, expensive speaker cable would make much of a difference with them. Perhaps ported speakers work better with high damping factors than aperiodic vented speakers, and perhaps some crossovers are "tuned" for use with certain amps.
It's unlikely any fat, expensive speaker cable would make much of a difference with them. Perhaps ported speakers work better with high damping factors than aperiodic vented speakers, and perhaps some crossovers are "tuned" for use with certain amps.
Indeed. A loudspeaker is a current sensitive transducer. The force on the cone is proportional to the magnet field strength, the length of wire in the gap, and the current. BIL
So indeed there is a successful history in using a transconductance amp, which has a current output proportional to the voltage input, to drive particularly a low frequency driver.
And then there is motional feedback. This is where the physical position of the cone is measured, and is used as feedback to the amplifier. So the amplifier works in such a way to put the cone precisely where it ought to be. It was pioneered by Philips in the 1970s and incorporated in products through the 1980's. Currently revived by this company https://www.grimmaudio.com/wordpres...al-feedback-essentials-Rob-Munnig-Schmidt.pdf
How do L-pad affect the damping factor?
Zload = looking through the L-pad to the load.
Zamp = looking through the L-pad to the amp.
Have I defined these correctly?
L-pad matches impedance in one direction, from amplifier to speaker. So Zload remains unchanged, but the speaker will see Zamp change.
Does anyone know of a reference where these equations for impedance mismatch are defined? (Yes I could work them out…)
Zload = looking through the L-pad to the load.
Zamp = looking through the L-pad to the amp.
Have I defined these correctly?
L-pad matches impedance in one direction, from amplifier to speaker. So Zload remains unchanged, but the speaker will see Zamp change.
Does anyone know of a reference where these equations for impedance mismatch are defined? (Yes I could work them out…)