Hi,
Could someone please explain what the damping factor of amps in the the specs is all about and how that relates to matching speakers?
Thanks
Lee
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Could someone please explain what the damping factor of amps in the the specs is all about and how that relates to matching speakers?
Thanks
Lee
Sent from my iPhone using Tapatalk
That article is a good start but it gets a lot more involved. A typical solid state amp will have a damping factor of 100 or more. But a SET amp may have a damping factor of 2 or 3. Most speakers now are designed to be run with an amp with a damping factor around 100 or greater and just won't preform as expected with an amp with a damping factor that's much less than 100. As you look at speaker design you will come across the term QTS. When you see a driver that says it had a QTS of .35 for example this is if it is connected to an amp with a high damping factor but hook it up to an amp with a low damping factor or a couple of ohms resistance in the crossover or speaker cables and the QTS could easily be .5 or higher sometimes a lot higher.
Woody gave a pretty good overview, but basically
Damping Factor is a pretty useless number that has very little meaning in real terms. In the real world with cables, speakers, and whatever the actual difference is very, very small. Don't bother worrying about it...McIntosh and Pass Labs certainly don't with their very low DF and I don't recall any complaints about any lack of bass!
Best Regards,
TerryO
Damping Factor is a pretty useless number that has very little meaning in real terms. In the real world with cables, speakers, and whatever the actual difference is very, very small. Don't bother worrying about it...McIntosh and Pass Labs certainly don't with their very low DF and I don't recall any complaints about any lack of bass!
Best Regards,
TerryO
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Damping Factor
Interesting where WOODY gets his facts from?
Most speakers now are designed to be run with an amp with a damping factor around 100 or greater and just won't preform as expected with an amp with a damping factor that's much less than 100.
What WOODY does not know that the damping factor of an amplifier is almost a useless specification in the real world
The amplifier can have a DF of 10,000 and one single fact I guess which eludes WOODY is that the DCR of the voice coil of the speaker is in series with the speaker circuit.
So the Zo of the amplifier is 0.0008 ohms, great. Now add in the resistances of all connections from amplifier's PCB through the speaker circuit and back to the PCB. Let's be generous and say this is 0.001 ohms.
So far Woody understands this.
Now add in the DCR of the say 4 ohm speaker, typically about 3.2 ohms
Now add the 3.2+0.001 + 0.0008 = 3.2018 ohms!
DF is defined as load impedance divided by Zo. But the effective Zo is 3.2018 ohms.
DF therefore is 4/3.2108 = 1.249.
The late Julian Hersch wrote a paper on this very subject.
I would like to know form WOODY what designs are implemented into "modern" speakers that makes them ONLY perform well with amplifiers with a DF of >100?
Interesting where WOODY gets his facts from?
Most speakers now are designed to be run with an amp with a damping factor around 100 or greater and just won't preform as expected with an amp with a damping factor that's much less than 100.
What WOODY does not know that the damping factor of an amplifier is almost a useless specification in the real world
The amplifier can have a DF of 10,000 and one single fact I guess which eludes WOODY is that the DCR of the voice coil of the speaker is in series with the speaker circuit.
So the Zo of the amplifier is 0.0008 ohms, great. Now add in the resistances of all connections from amplifier's PCB through the speaker circuit and back to the PCB. Let's be generous and say this is 0.001 ohms.
So far Woody understands this.
Now add in the DCR of the say 4 ohm speaker, typically about 3.2 ohms
Now add the 3.2+0.001 + 0.0008 = 3.2018 ohms!
DF is defined as load impedance divided by Zo. But the effective Zo is 3.2018 ohms.
DF therefore is 4/3.2108 = 1.249.
The late Julian Hersch wrote a paper on this very subject.
I would like to know form WOODY what designs are implemented into "modern" speakers that makes them ONLY perform well with amplifiers with a DF of >100?
Concentrate on amplifier output impedance and how it varies over the Audio Frequency Range.
Compare that VARIABLE Output Impedance tot he other impedances between the amp output and the speaker voice coil.
I'll guarantee that a Retailer of an amplifier that claims a DF=1000 will not have any data for what happens at any other spot frequency.
Ignore DF, it is irrelevant.
Compare that VARIABLE Output Impedance tot he other impedances between the amp output and the speaker voice coil.
I'll guarantee that a Retailer of an amplifier that claims a DF=1000 will not have any data for what happens at any other spot frequency.
Ignore DF, it is irrelevant.
Damping factor of an amplifier results from a calculation of the ratio of an arbitrary impedance (usually 8 Ohm resistive) to the output impedance of this amp (at what frequency ?).
It is a nebulous and naughty concept.
Suppose that the amp output voltage increases with increasing output current.
It sometimes happens when the amp has what is called a negative output impedance.
Well mastered, it is a technique which can be useful.
What is the meaning of damping factor, then ?
Think of output impedance and include it in series with Re and Le in the usual modelisation of a driver, and you'll definitely master how the main resonance of a driver is damped and will forget damping factor for ever.
It is a nebulous and naughty concept.
Suppose that the amp output voltage increases with increasing output current.
It sometimes happens when the amp has what is called a negative output impedance.
Well mastered, it is a technique which can be useful.
What is the meaning of damping factor, then ?
Think of output impedance and include it in series with Re and Le in the usual modelisation of a driver, and you'll definitely master how the main resonance of a driver is damped and will forget damping factor for ever.
Here is a sample of an available chart. Apparently the DF is not useful at higher frequencies. I don't know if this is an amplifier limitation or if it relates to the usefulness of a speaker in it's behaviour.
I recall that NP has described using a resistor in series with speaker out, close to the amplifier, to decrease DF in order to provide more bass, if needed. Are you saying that this is never required for high-fidelity solid state amps (not guitar amps)? Or, perhaps, that a tone control can simply take care of the issue in most instances?
Thanks.
Thanks.
I can easily hear the difference between a DF of 20 or 100 with my 15 inch Tannoys DC at low frequencies . It's not a matter of less or more bass , but more precise bass !( Using adequate proportioned speaker cables and XO components )
I see the DF as an electric brake on the big heavy cone . If the bass tone stops , the cone stops due to the low output resistance of the amp . without the "brake" the cone keeps resonating a bit
I don't hear any difference above a DF of 100 ( have an amp with a DF of 3000 at 20Hz ) Don't think it has any effect on higher frequencies , can't hear any difference .
Cheers ,
Rens
I see the DF as an electric brake on the big heavy cone . If the bass tone stops , the cone stops due to the low output resistance of the amp . without the "brake" the cone keeps resonating a bit
I don't hear any difference above a DF of 100 ( have an amp with a DF of 3000 at 20Hz ) Don't think it has any effect on higher frequencies , can't hear any difference .
Cheers ,
Rens
The DF only actually achieves anything at low woofer frequencies. Get a typical woofer, unconnected to an amp, put your ear close to it and tap the pad of your finger on the cone - you'll hear its fundamental resonant frequency sound out. Now short the woofer terminals and repeat - it will be much quieter and fade away much quicker.
When an amp is connected it will do much the same, making for a tighter bass with music signal, but even a couple of ohms output impedance will do much the same for reasons already given, so DF isn't too important as long as it's more than a few.
When an amp is connected it will do much the same, making for a tighter bass with music signal, but even a couple of ohms output impedance will do much the same for reasons already given, so DF isn't too important as long as it's more than a few.
Hmmm..
I found that the instantaneous Current delivery Capacity of an Amp was THE critical factor in getting My DC's to have sparkling Dynamics.
Decades of dicking around to realize that tho 😱
Those big heavy LF cones seem to thrive with currents adequate to control them against their Large alnicos.
Damping factors, I perhaps mistakenly 🙂 understood to be simply Brochure babble.
I found that the instantaneous Current delivery Capacity of an Amp was THE critical factor in getting My DC's to have sparkling Dynamics.
Decades of dicking around to realize that tho 😱
Those big heavy LF cones seem to thrive with currents adequate to control them against their Large alnicos.
Damping factors, I perhaps mistakenly 🙂 understood to be simply Brochure babble.
eldarvanyar. i'm going with TerryO on this one. damping factor is a holdover from tube amplifier design. because of the sloppiness of the output transformer if you had a damping factor of 5 you were doing pretty good. my calculations say that a damping factor of 20 or higher is all you need.
lets say you are driving an 4 ohm speaker with an amp with a damping factor of 200. take 4 ohms, divide it by 200 = .02 ohms. thats the output impedance of the amplifier. when you ad in the speaker wire resistance it goes way down. a 10 foot pair of 14 ga wire has a restance of .05 ohms. .02 + .05 = .07. 4 ohms divided by .07 equals a damping factor of 57, thats only 10 feet of wire and that doesn't even include the dc resistance of the speaker which lowers it even more. this is all based on the idea that speaker design is an exact science, lets face it's not. go look at the efficiency of a speaker sometime.
wadest
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As Moer (post #6) and others said.
It is not that the DF is useless, its only that the definition of (loudspeaker impedance)/(amplifier output impedance plus cable) shows ignorance of how electricity works. Perhaps in different words: The braking of a loudspeaker is achieved by the maximum 'counter' or braking current it can generate when signal stops. That is limited by the total circuit resistance - the voice coil dc resistance does not suddenly disappear from the complete circuit! As said for a 4 ohm loudspeaker; for an 8 ohm driver the voice coil resistance is at least 5,5 ohm in practice, giving a maximum possible real df of 1,6 except at bass resonance. There, greatly depending on the enclosure design, the figure might become some 4.
Amplifier-wise the output resistance does (or should!) remain pretty constant over the audio region, but again it does not count as explained. Also at high frequencies the loudspeaker cone becomes velocity-controlled and electromagnetic braking is less important. There are also reactive components from the loudspeaker etc.; as said it becomes complex, but the main limitation remains the loudspeaker. (This of course excluding active circuitry where the amplifier output impedance can be made negative. Then there is a real possibility of doing some serious loudspeaker control ... and also of instability if the designer is not careful.)
Sorry for repetition but this understanding is generally overlooked. (With all respect to members hearing the effect of dfs over a spec.-ed say 20 - you will have to look elsewhere for what you perceive; certainly not at the published amplifier df. If you have experienced this with different dfs from different amplifiers and not the otherwise same one, that is a whole different story.)
It is not that the DF is useless, its only that the definition of (loudspeaker impedance)/(amplifier output impedance plus cable) shows ignorance of how electricity works. Perhaps in different words: The braking of a loudspeaker is achieved by the maximum 'counter' or braking current it can generate when signal stops. That is limited by the total circuit resistance - the voice coil dc resistance does not suddenly disappear from the complete circuit! As said for a 4 ohm loudspeaker; for an 8 ohm driver the voice coil resistance is at least 5,5 ohm in practice, giving a maximum possible real df of 1,6 except at bass resonance. There, greatly depending on the enclosure design, the figure might become some 4.
Amplifier-wise the output resistance does (or should!) remain pretty constant over the audio region, but again it does not count as explained. Also at high frequencies the loudspeaker cone becomes velocity-controlled and electromagnetic braking is less important. There are also reactive components from the loudspeaker etc.; as said it becomes complex, but the main limitation remains the loudspeaker. (This of course excluding active circuitry where the amplifier output impedance can be made negative. Then there is a real possibility of doing some serious loudspeaker control ... and also of instability if the designer is not careful.)
Sorry for repetition but this understanding is generally overlooked. (With all respect to members hearing the effect of dfs over a spec.-ed say 20 - you will have to look elsewhere for what you perceive; certainly not at the published amplifier df. If you have experienced this with different dfs from different amplifiers and not the otherwise same one, that is a whole different story.)
bonsai, i agree with you completely. I just wasn't sure weater they wouldn't understand exactly how adding the dc resistance effects everything.
For every loudspeaker there is an optimum amplifier output impedance... sometimes that means adamping factorof less than 1 (rarely today given that we live in a world dominated by speakers that assume a voltage amplifier)
It is important to remember that the amplifier/cable/speaker are a system and should nott really be considered as 3 separate pieces.
dave
It is important to remember that the amplifier/cable/speaker are a system and should nott really be considered as 3 separate pieces.
dave
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