The term "inductance" means.. The relationship between the current flowing through a system, and the energy that is stored within the magnetic field as a result.
E = 1/2 L*I*I
This relationship holds even at DC, there is energy being stored within the magnetic field.
At DC, there is a uniform current density flowing within the wire. At DC, the magnetic flux is a linear function of the radius of the conductor within the conductor, and has a 1/r relationship outside the wire.
When the current within the wire is changing, the eddy currents within the wire cause the current to shift outward. At infinite frequency, all of the current will be at the surface of the conductor, and also there will be no magnetic field inside the conductor.
Mathematically, the equation for the inductance within a cylindrical conductor carrying DC current is L = mu / (8 * pi).
Outside, the inductance is calculated by adding up all the magnetic energy that is outside the wire. This involves integrating the field to infinity, and the result is infinite energy. This of course is not what happens. The return current has an opposite field, so cancellation occurs, and one does not have to go to infinity to get an answer out to 10 digits precision.
The equations that have been presented in the links given assume the return current is somewhere, but it is not defined within the text of the links. DB mentions that their form is consistent with a large wire loop with return current "somewhere", but again, what parameters? Historically speaking, that "somewhere" was sufficient for the needs of the time (1908). But one must use those equations with the caveat that the equations may not be consistent with what was needed in this time.
To change the current within an inductor, one has to place a voltage across it's terminals. That voltage charges the inductor at a specific rate of change of the current. The reactance you mention is simply a relationship between the inductance and the current resulting from an ac voltage..
Why would DC be a strange choice for me?? It is the normal method of powering a superconducting magnet..
ps..I have attached an analysis scan showing the magnetic field intensity of a cylindrical conductor. The top is the wire, the bottom is the field magnitude plot. Note that on the far right the field magnitude is zero, this at the center of the wire. It increases linearly as you head to the wire surface. At the surface, it changes into the 1/r function. It never reaches zero, as this is a plot of a wire without a return conductor.
Cheers, John
Thanks for clearing that up.
"Why would DC be a strange choice for me?? "
Because inductance is customarily thought of for its reactive impedance which is a function of frequency. At DC there is no reactive impedance, the only limit to current flow in an LR circuit is DC resistance. Once the field is established and stable after the initial turn on transient current that's it. I assume that the reactive impedance comes about from the tendency of the field to resist change by generating a reverse emf as the field collapses.
I guess it depend on the crowd you hang out with. you know, potato, potahto..
The discussion was about inductance, not reactive impedance, so I fashioned my response with inductance.
My little world worries about the stored energy first. Then, how fast the current rises when you put voltage on the terminals. Then, how much voltage we can live with when we turn it off..
For wires and inductance, I'd really consider them as DC for audio frequencies, as the inductance drop is rather small for audio frequencies.
Cheers, Jn
Back on topic, please. OT posts deleted. Stay on topic or the thread gets closed.Ballanced connections must have the same impedance for positive and negative connections. Or else CMMR goes through the roof. Trannies are best here, but you can use bootstrapped inputs to.
The pin 1 problem has nothing to do with that. This problem arises when you want to connect a ballanced system to an unballanced system. Now signal earth and chassis earth are connected and a very loud buzzing noise is heard (groundloop). The propper solution would be to use a trannie or DI input. But because this is more expencive, manufacterers leave these out. What they do is simply disconnect the chassis earth and connect the shield to signal earth. Now you do not have a ballanced connection anymore and RFI and magnetic interference go straight into the audio path. But no loud buzzing sound anymore. High resolution audio is not possible anymore though.
You`re still the one who`s closest to the thruth so far, just don`t let them confuse you
Hmm, the usual cable thread with the usual suspects contributing their usual efforts to demonstrate how clever they are without regard to the fact that in the process they increase the scope for the unscrupulous to exploit the unwary and less well informed.
When are you guys going to learn to keep your putative expertise to yourselves and confine yourselves to simply stating the obvious truth that it will be an extremely unusual cable in an unusual system where any audible effect is perceptible and that these findings are borne out by all logic, instrumentation and the only objective tests available?
No names, no pack drill.
When are you guys going to learn to keep your putative expertise to yourselves and confine yourselves to simply stating the obvious truth that it will be an extremely unusual cable in an unusual system where any audible effect is perceptible and that these findings are borne out by all logic, instrumentation and the only objective tests available?
No names, no pack drill.
There's only one requirement for a speaker connecting lead, and that's low resistance to allow good damping of the driver. Skin effect is negligable at the upper limit of human hearing so we don't really need to consider this on reasonably sized conductors.
What needs to happen perhaps is for one of the worshipers of expensive cables to unwind a speaker voice coil and compare the wire it is wound from with the expensive stuff he's using to connect the amp to it.
I think that would probably put this whole issue into perspective.
What needs to happen perhaps is for one of the worshipers of expensive cables to unwind a speaker voice coil and compare the wire it is wound from with the expensive stuff he's using to connect the amp to it.
I think that would probably put this whole issue into perspective.
Hi,
First, there are enough who have performed tests with a varying degree of "blindness" who will disagree on the audibility.
By simply denying that this audibility exists and by insisting that no measurements exist that allow us to quantify the respective goodness or not of a given cable, a situation is created in which any snake oil may be sold easily as many who prefer to trust the evidence of their senses more than any dogmatic, rhetorical, categorical, unqualified and hence reliably wrong statement to the contrary.
By denying the value of investigation using method's other than subjective listening (by pre-judging that no differences are measurable) a door is closed and bricked up that may otherwise allow a way out.
This tenet of the objectivist faith that speaker cables (actually all cables) must not make a difference is the high of unscientific behaviour, equalling that of the sellers of cables marketed in obvious opposition to physical reality...
Ciao T
First, there are enough who have performed tests with a varying degree of "blindness" who will disagree on the audibility.
By simply denying that this audibility exists and by insisting that no measurements exist that allow us to quantify the respective goodness or not of a given cable, a situation is created in which any snake oil may be sold easily as many who prefer to trust the evidence of their senses more than any dogmatic, rhetorical, categorical, unqualified and hence reliably wrong statement to the contrary.
By denying the value of investigation using method's other than subjective listening (by pre-judging that no differences are measurable) a door is closed and bricked up that may otherwise allow a way out.
This tenet of the objectivist faith that speaker cables (actually all cables) must not make a difference is the high of unscientific behaviour, equalling that of the sellers of cables marketed in obvious opposition to physical reality...
Ciao T
Hi,
Clearly not, as the driver usually has a DCR of more than 70% of it's nominal impedance (usually not garanteed with better than 10% precision by the driver makers), so the impact on the damping of the driver between a pure zero ohm connection and cable with 10% of the DCR of the driver is neglible.
So clearly, this view is wrong.
Please clarify what constitutes "negligable effect" (how many dB or degrees phaseshift, with evidence based on the humans hearings sensitivity in relation to the conducutor size you call "reasonable". Without qualifying and quantifying your statement it is full of weaselwords and devoid of actual meaning.
The voice coil wire is solid core, round, copper in most cases. This is the same type of wire I use in my speaker cables.
Yes, it does. It shows that most speaker cables are stranded and fat, while the voice coil wire is thin and solid core. I know many advocate the use of solid core wires and of relatively small diameter (compared to these He-Man 10 Gauge stuff), is that what you are getting at?
If find this difficult to square with your earlier statements.
Ciao T
Clearly not, as the driver usually has a DCR of more than 70% of it's nominal impedance (usually not garanteed with better than 10% precision by the driver makers), so the impact on the damping of the driver between a pure zero ohm connection and cable with 10% of the DCR of the driver is neglible.
So clearly, this view is wrong.
Please clarify what constitutes "negligable effect" (how many dB or degrees phaseshift, with evidence based on the humans hearings sensitivity in relation to the conducutor size you call "reasonable". Without qualifying and quantifying your statement it is full of weaselwords and devoid of actual meaning.
The voice coil wire is solid core, round, copper in most cases. This is the same type of wire I use in my speaker cables.
Yes, it does. It shows that most speaker cables are stranded and fat, while the voice coil wire is thin and solid core. I know many advocate the use of solid core wires and of relatively small diameter (compared to these He-Man 10 Gauge stuff), is that what you are getting at?
If find this difficult to square with your earlier statements.
Ciao T
I wonder for the exotic cable advocates that if you had a friend come over and do this type of experiment, would you really notice the difference and pick your cable?
Example: Testing your exotic/preferred speaker cables against two cheapo cable brands of the same gauge and length. You are out of the room and nowhere near it to hear anything.. Your trusted friend either changes the cables or not, then brings you into the room blindfolded and sits you in your listening chair and cues up a favorite piece of music that you've preselected. You sit and listen for round one, and make a check or an x if it's your cables or not.. He/she takes you out of the room and out of hearing range again, then changes the cables or not and brings you back in for round two.. Repeat all this again then take a break.. Don't go over the results and do the whole experiment again 3 times, take a break.. Don't go over the results and do the whole experiment again 3 times..
So now you have heard your cables 3 times and each cheapo cable 3 times on 3 separate sessions, for a total of 9 times hearing your preselected track of music.
How many times after listening blindfolded to your preselected track of music did you notice when your cables were used against the other brands??
Now try that with different speaker drivers and you will pick out the change quite easily..
My point/two cents: if you have the money to burn or just feel better knowing you have a great wonder cable in your system then all the best, but imo the money would be better invested into other aspects of the system or room etc
Disclaimer: I use a full Cat5 cable for each left and right channel, cheap and works for me
Example: Testing your exotic/preferred speaker cables against two cheapo cable brands of the same gauge and length. You are out of the room and nowhere near it to hear anything.. Your trusted friend either changes the cables or not, then brings you into the room blindfolded and sits you in your listening chair and cues up a favorite piece of music that you've preselected. You sit and listen for round one, and make a check or an x if it's your cables or not.. He/she takes you out of the room and out of hearing range again, then changes the cables or not and brings you back in for round two.. Repeat all this again then take a break.. Don't go over the results and do the whole experiment again 3 times, take a break.. Don't go over the results and do the whole experiment again 3 times..
So now you have heard your cables 3 times and each cheapo cable 3 times on 3 separate sessions, for a total of 9 times hearing your preselected track of music.
How many times after listening blindfolded to your preselected track of music did you notice when your cables were used against the other brands??
Now try that with different speaker drivers and you will pick out the change quite easily..
My point/two cents: if you have the money to burn or just feel better knowing you have a great wonder cable in your system then all the best, but imo the money would be better invested into other aspects of the system or room etc
Disclaimer: I use a full Cat5 cable for each left and right channel, cheap and works for me
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+1
No offense to the OP, but these matters have been discussed, rehashed, and rehashed on this website and I'm sure plenty of others. I'm of the feeling that there's far better to be utilizing our storage/bandwidth on, than repeating discussions on what is clearly a matter of personal taste and income bracket.
Confusion and agendas
Folks,
There seems to be a perennial confusion in these cable debates, made worse by agendas that cause more confusion.
Let us be clear, there is no point debating if a cable is expensive or cheap, it has little to do with the effects that cause differences in cables. Those who debate in terms of cheap or expensive cables have an agenda that has nothing to do with anything technical or objective, but all with value judgements and prejudice.
Further, the term exotic applied to cables does not help. What is an exotic cable? One with lime green sleeving, one that differs in other parameters from a completely illusionary "average" or "ideal" cable? Again, those who debate "exotic cables" and "normal cables" have an agenda that has nothing to do with anything technical or objective, but all with value judgements and prejudice.
Neither agenda is relevant to or even interested in the truth about cables and can safely been ignored.
What does matter here actually is if there are parameters in the cables that may give rise to changes in the sound and/or measured performance of a system comprised of said cable, an attached load (commonly a speaker) and an Amplifier (which may be constructed freely with a range of technologies and circuit designs etc.).
Non of the parameters we need consider contain "price" or "exotic or not".
What I will say here is, that without going into audibility, blind testing etc. et al, we can observe measured problems stemming from factors other than the simple lumped LCR model of the cable and it's influence on the signal passing through the cable (e.g. it's action as aerial towards RF, which in turn can enter the amplifier through the speaker connections).
This is not to say that L/C/R have no effect, they have and they must be accounted for, but these effects are not all that must be accounted for.
Now to move on to blind testing, if implemented correctly they are valuable means of eliminating bias from observation. However they are subject to limitations and issues that make small scale listening tests largely meaningless, especially if implemented subjects that are aware of the phenomena being tested and that have a definite opinion of what the outcome should be.
I have repeatedly cited the example of the "Cable Skeptic", who when told he was hearing different mains cables in fact failed to observe any difference. He also huffing and puffing stormed out shouting fraud when told that what he actually had failed to hear was not the difference between different cables, as he had been told, but the reversal of the polarity in one channel of the system...
Those who insist their small scale blind test with prejudiced subjects are being no more scientific than those who insist their sighted tests have generalised applicability.
This is not to say that such a test is necessarily useless to an individual. We may draw our own personal conclusions from all sorts tests, including, but not limited to technical measurements, sighted listening tests, single-blind preference tests test, fully double blind AB tests etc.
It helps if place our result from any such test in the context of a confidence interval, which tells us how confident we can be our outcome reflected the true situation. If for example measurements show poor repeatability, we can not have a great deal of confidence that they reflect reality, however, equally null results in small scale blind tests, even if easily repeatable cannot give much confidence that we have not missed significant phenomena...
So we come to the point that there are many casual, small scale listening tests, some of which are blind, others of which are not and all of which in terms of statistical significance amount not even to hill of beans, but a big fat nothing, no matter what importance individuals apply to them.
We have much anecdotal evidence that cables make a difference and some published blind tests whose statistics render powerless in a statistical sense that claim the opposite. On balance we can only conclude "more data needed".
Where does all that leave us then?
Use whatever satisfies your value system, your concepts of reality and your desires as speaker (and other) cables. As Peter Walker once very deadpan remarked when questioned on the most important parameter in speaker cables, it is the length.
The cable must be long enough to make a connection, a truly night and day difference is observable between a cable that is too short and one of the right length.
All else is secondary and can be fun to experiment with, if one has the time, fun to debate, if one has the time but any hope for definite conclusions, any absolutes or a "final solution" is as futile as to go hunting the Snark... So be kind and tolerant to those who happen to be hunting a different colour snark from that you are hunting...
Ciao T
They sought it with thimbles, they sought it with care;
They pursued it with forks and hope;
They threatened its life with a railway-share;
They charmed it with smiles and soap.
Lewis Carroll - The Hunting of the Snark
Folks,
There seems to be a perennial confusion in these cable debates, made worse by agendas that cause more confusion.
Let us be clear, there is no point debating if a cable is expensive or cheap, it has little to do with the effects that cause differences in cables. Those who debate in terms of cheap or expensive cables have an agenda that has nothing to do with anything technical or objective, but all with value judgements and prejudice.
Further, the term exotic applied to cables does not help. What is an exotic cable? One with lime green sleeving, one that differs in other parameters from a completely illusionary "average" or "ideal" cable? Again, those who debate "exotic cables" and "normal cables" have an agenda that has nothing to do with anything technical or objective, but all with value judgements and prejudice.
Neither agenda is relevant to or even interested in the truth about cables and can safely been ignored.
What does matter here actually is if there are parameters in the cables that may give rise to changes in the sound and/or measured performance of a system comprised of said cable, an attached load (commonly a speaker) and an Amplifier (which may be constructed freely with a range of technologies and circuit designs etc.).
Non of the parameters we need consider contain "price" or "exotic or not".
What I will say here is, that without going into audibility, blind testing etc. et al, we can observe measured problems stemming from factors other than the simple lumped LCR model of the cable and it's influence on the signal passing through the cable (e.g. it's action as aerial towards RF, which in turn can enter the amplifier through the speaker connections).
This is not to say that L/C/R have no effect, they have and they must be accounted for, but these effects are not all that must be accounted for.
Now to move on to blind testing, if implemented correctly they are valuable means of eliminating bias from observation. However they are subject to limitations and issues that make small scale listening tests largely meaningless, especially if implemented subjects that are aware of the phenomena being tested and that have a definite opinion of what the outcome should be.
I have repeatedly cited the example of the "Cable Skeptic", who when told he was hearing different mains cables in fact failed to observe any difference. He also huffing and puffing stormed out shouting fraud when told that what he actually had failed to hear was not the difference between different cables, as he had been told, but the reversal of the polarity in one channel of the system...
Those who insist their small scale blind test with prejudiced subjects are being no more scientific than those who insist their sighted tests have generalised applicability.
This is not to say that such a test is necessarily useless to an individual. We may draw our own personal conclusions from all sorts tests, including, but not limited to technical measurements, sighted listening tests, single-blind preference tests test, fully double blind AB tests etc.
It helps if place our result from any such test in the context of a confidence interval, which tells us how confident we can be our outcome reflected the true situation. If for example measurements show poor repeatability, we can not have a great deal of confidence that they reflect reality, however, equally null results in small scale blind tests, even if easily repeatable cannot give much confidence that we have not missed significant phenomena...
So we come to the point that there are many casual, small scale listening tests, some of which are blind, others of which are not and all of which in terms of statistical significance amount not even to hill of beans, but a big fat nothing, no matter what importance individuals apply to them.
We have much anecdotal evidence that cables make a difference and some published blind tests whose statistics render powerless in a statistical sense that claim the opposite. On balance we can only conclude "more data needed".
Where does all that leave us then?
Use whatever satisfies your value system, your concepts of reality and your desires as speaker (and other) cables. As Peter Walker once very deadpan remarked when questioned on the most important parameter in speaker cables, it is the length.
The cable must be long enough to make a connection, a truly night and day difference is observable between a cable that is too short and one of the right length.
All else is secondary and can be fun to experiment with, if one has the time, fun to debate, if one has the time but any hope for definite conclusions, any absolutes or a "final solution" is as futile as to go hunting the Snark... So be kind and tolerant to those who happen to be hunting a different colour snark from that you are hunting...
Ciao T
They sought it with thimbles, they sought it with care;
They pursued it with forks and hope;
They threatened its life with a railway-share;
They charmed it with smiles and soap.
Lewis Carroll - The Hunting of the Snark
Interesting. A person who makes claim X (presumably on the basis of the physics he believes) failed to hear change Y (unrelated to X). And this demonstrates what? Everybody who makes physics-based claims has poor hearing?ThorstenL said:
I am sure Thorsten is not claiming this, because he knows you can't prove something from one example. So what does it show? One person, who believes in physics, was unable to hear a change which one might reasonably expect most audio fans to notice, and he got upset when he realised this. Bear in mind that he might have been listening for noise and distortion, not stereo imaging, or maybe he wasn't really listening at all.
I've cited the Greiner and Davis papers. A little googling will find lots of other people who have done blind listening tests of cables and found exactly what I described as "incontrovertible" several pages ago in Post 21.
If there are reliable controlled listening tests showing effects from other causes audible to others, I'd be interested in cites.
If there are reliable controlled listening tests showing effects from other causes audible to others, I'd be interested in cites.
Should have left out the words "expensive" and "exotic".. Try that experiment with "any" suitable speaker cable of the same length and gauge, and imo you will not guess your cable played those three times out of nine accurately..
But yes this is unproved until people try it, so on to better things for me
Cheers
But yes this is unproved until people try it, so on to better things for me
Cheers
Transmission Line effects in speaker cables
Speaker cables are transmission lines, and we must be careful not to rely too much on the lumped LCR model. As a result, speaker cables can sometimes affect the sound in ways that are not intuitive or are dependent on the amplifier or loudspeaker.
We have all heard stories about how cables with very high capacitance can cause trouble with certain amplifiers, but there can be more to the story.
It is certainly true that the quarter-wave length of a typical louspeaker cable at even 20 kHz is very long, there are effects well above the audio range that can affect the stability of an amplifier.
In my book "Designing Audio Power Amplifiers" I have in Chapter 18 results of impedance measurements of a typical 10-foot loudspeaker cable when the far end is unterminated, terminated in its characteristic impedance, and terminated in a short. The transmission line effects are strongly visible in the 1 - 100 MHz frequency range. Different loudspeakers often act as vastly different terminating impedances at these frequencies. Note that the characteristic impedance of a length of audio-grade cable of ZIP-like construction is typically in the neighborhood of 100-120 ohms.
Wild impedance variations at out-of-band high frequencies can destabilize some amplifiers, sometimes conditionally. Highly mis-terminated speaker cables can sometimes also act more efficiently as an antenna for RFI at certain frequencies (or amplifiy the effects of the loudspeaker acting as an antenna).
Some people have claimed improvements by including a series R-C Zobel network across the loudspeaker terminals to more properly terminate the loudspeaker cable a high frequencies.
Cheers,
Bob
Speaker cables are transmission lines, and we must be careful not to rely too much on the lumped LCR model. As a result, speaker cables can sometimes affect the sound in ways that are not intuitive or are dependent on the amplifier or loudspeaker.
We have all heard stories about how cables with very high capacitance can cause trouble with certain amplifiers, but there can be more to the story.
It is certainly true that the quarter-wave length of a typical louspeaker cable at even 20 kHz is very long, there are effects well above the audio range that can affect the stability of an amplifier.
In my book "Designing Audio Power Amplifiers" I have in Chapter 18 results of impedance measurements of a typical 10-foot loudspeaker cable when the far end is unterminated, terminated in its characteristic impedance, and terminated in a short. The transmission line effects are strongly visible in the 1 - 100 MHz frequency range. Different loudspeakers often act as vastly different terminating impedances at these frequencies. Note that the characteristic impedance of a length of audio-grade cable of ZIP-like construction is typically in the neighborhood of 100-120 ohms.
Wild impedance variations at out-of-band high frequencies can destabilize some amplifiers, sometimes conditionally. Highly mis-terminated speaker cables can sometimes also act more efficiently as an antenna for RFI at certain frequencies (or amplifiy the effects of the loudspeaker acting as an antenna).
Some people have claimed improvements by including a series R-C Zobel network across the loudspeaker terminals to more properly terminate the loudspeaker cable a high frequencies.
Cheers,
Bob
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