Damping factor of 100 at 10KHz? - diyAudio
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Old 30th September 2014, 03:06 PM   #1
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Default Damping factor of 100 at 10KHz?

Agreed that the DF is immaterial if the cable has enough resistance but i have listened couple of amps having such high figures it even means DF at 100Hz is 10000 hence super grip even with cable resistance this will endup having a DF of in the order of 500 which is more than sufficient.

What are the ways to reduce output impedance adding more output pairs? How many required to get the DF at 10K to be 100. Is there any connection between the DF and Freq response of the amplifier? like extended upper freq like more than 100KHz has better grip at lower frequencies?
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Old 30th September 2014, 03:14 PM   #2
rayma is online now rayma  United States
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Originally Posted by rhythmsandy View Post
Agreed that the DF is immaterial if the cable has enough resistance but i have listened couple of amps having such high figures it even means DF at 100Hz is 10000 hence super grip even with cable resistance this will endup having a DF of in the order of 500 which is more than sufficient.

What are the ways to reduce output impedance adding more output pairs? How many required to get the DF at 10K to be 100. Is there any connection between the DF and Freq response of the amplifier? like extended upper freq like more than 100KHz has better grip at lower frequencies?
There's no way to do this without placing the amp right at the driver.
With #6 wire, using three feet long conductors, the loop resistance is 0.025 Ohms. (There is also inductance to consider at HF.)
With an 8 Ohm driver, this gives DF = 320. Even using remote sensing is unlikely to improve things much.

Last edited by rayma; 30th September 2014 at 03:17 PM.
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Old 30th September 2014, 03:34 PM   #3
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Originally Posted by rayma View Post
There's no way to do this without placing the amp right at the driver.
With #6 wire, using three feet long conductors, the loop resistance is 0.025 Ohms. (There is also inductance to consider at HF.)
With an 8 Ohm driver, this gives DF = 320. Even using remote sensing is unlikely to improve things much.
Agreed im talking only on the specification point of view not on resultant DF when wire used..

Just on the amp specwise...
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Old 30th September 2014, 03:55 PM   #4
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But why? This is one of those specs where the engineering rule of ten applies, Once you get lower than 0.5 Ohm, nothing significant can be achieved and you are creating all manner of stability problems trying
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Old 30th September 2014, 03:59 PM   #5
Bare is offline Bare  Canada
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Why? are you finding this a problem?? Speakers not of decent enough quality to manage Non farty bass or decent dynamics.
Some ARE better than others :-)

Last edited by Bare; 30th September 2014 at 04:01 PM.
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Old 30th September 2014, 04:01 PM   #6
rayma is online now rayma  United States
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Originally Posted by davidsrsb View Post
But why? This is one of those specs where the engineering rule of ten applies, Once you get lower than 0.5 Ohm, nothing significant can be achieved and you are creating all manner of stability problems trying
Some of the improvements heard with a lower source resistance to the speaker are due to the crossover's impedance acting as a voltage divider.
See one of the Stereophile amplifier reviews for how this can add significant frequency response aberrations.
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Old 30th September 2014, 04:09 PM   #7
jcx is offline jcx  United States
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not a problem for a high feedback amp at its output terminals

Kelvin sensing to high audio frequency at home audio speaker cable lengths is also not really hard, cable construction isn't trivial though, "quadaxial" 4 signal conductor layer coax cables?
feedback may need some modification for the cable Z (Cload)

a 3rd way is synthesizing negative audio frequency impedance amplifier output with mixed feedback - such that it cancels most of the audio frequency cable R
again fun feedback problem - minor issue of amp output sticking to tails when not loaded...


but as others mention it seems a unlikely "solution" with real Loudspeaker loads, their XO components R

Last edited by jcx; 30th September 2014 at 04:12 PM.
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Old 30th September 2014, 06:33 PM   #8
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Yes lpf inductor at woofer generally swomps out the DF so definitely need an amp with very high df.
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Old 30th September 2014, 06:48 PM   #9
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A couple of things:

Firstly, there is no difficulty in getting the output impedance down to something like 0.02 Ohm without any special measures or any problems with stability.

Secondly, the biggest resistance in the circuit is not the cabling but the resistance of the voice-coil. That will be around 7 Ohm for a unit with a nominal 8 Ohm impedance. This swamps all other resistances.
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Last edited by DouglasSelf; 30th September 2014 at 06:50 PM.
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Old 30th September 2014, 06:50 PM   #10
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Quote:
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a 3rd way is synthesizing negative audio frequency impedance amplifier output with mixed feedback - such that it cancels most of the audio frequency cable R
again fun feedback problem - minor issue of amp output sticking to tails when not loaded...
Do you know of a solid-state example of this? I'd be interested to see it.
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