Bi-wiring Part 2: The Cable Conundrum

[admin]

One of the arguments presented in the web forum thread I’ve already examined on a previous article is that there is a difference between a bi-wired speaker system and conventional wiring due to a difference in their cable power dissipation behaviours. So let’s examine the systems described in the thread and see what difference there may be between them in practice.

Discuss "Bi-wiring Part 2: The Cable Conundrum" here. View the article at:
http://www.audioholics.com/education/cables/bi-wiring-part-2-the-cable-conundrum.

 

[jneutron]

One of the arguments presented in the web forum thread I’ve already examined on a previous article is that there is a difference between a bi-wired speaker system and conventional wiring due to a difference in their cable power dissipation behaviours. So let’s examine the systems described in the thread and see what difference there may be between them in practice.

Discuss "Bi-wiring Part 2: The Cable Conundrum" here. View the article at:
http://www.audioholics.com/education/cables/bi-wiring-part-2-the-cable-conundrum.

Nice. Thanks for putting the link up. Could you fix those apostrophies?..

Ok, where to start...

In Modulation muddle, the following:
I was quoted saying(highlights mine)

The result? In a monowire setup, the current of one signal will modulate the losses that are caused by the other...

Jims verbage:

The conclusion of the above argument is that the current for one signal component “modulates” that for the others, and hence creates a form of ‘intermodulation distortion’ (as is claimed in other postings in the web forum thread).

Hmmm...apparently "modulate the losses" means "intermodulation distortion.", which was not what I said there. I said the current of one will modulate the losses of the other. That seems a simple enough sentence. Any deviation of one signal as a result of another is indeed distortion, and the fact that another signal caused it is indeed classified as an intermodulation effect. That does not mean it will show up using the classical definition of IM distortion.

And now, lo and behold...there is indeed the dissipation modulation I specified in detail, here's jim's "new" verbage: (highlights mine)

The above results do seem to present us with an anomaly or paradox, as described in the web thread. The signal power level and current injected into the system by the amplifier is identical in both arrangements. Each speaker unit has the same power, current, and voltage delivered to it with both arrangements. Yet the cable loss patterns are different! The monowired case shows a ‘cross product’ term involving both signal frequencies which is absent when the system is bi-wired.

hmmm..again, this is precisely what I said..If one recalls my "2AB" part.

interesting..Now, for the conclusions from the first page :

The claim muddles time variations in the power level with time variations in the voltage and current.

No, it presented exactly the dissipation variations caused by monowiring vs biwiring. This fact is indeed confirmed by Jims "new and improved" page.

It confuses the effect of a square-law relationship between current or voltage and power with a claimed effect of the presence of cable resistance.

No, it presents exactly the square law relationship between current and dissipation within the wire.

It directs attention onto the power dissipation in the cable, and away from considering the signal voltage, current, and power patterns at the speaker.

No, it presents the difference between wire losses in each case. Again, jim did a bang up job in presenting graphs in the new and improved page, again confirming exactly what I've said.

Focussing on the cable, it does not notice that the voltage, current, and power patterns at the speaker and amplifier output have the same shapes with or without the cable resistance.

hmm...amp applies voltage, cables have different losses, yet speakers react the same even though one wireset dissipates differently from the other..

Gee, that is indeed a conundrum...

This paragraph is the far more interesting one, this from the new and improved page.

The signal power level and current injected into the system by the amplifier is identical in both arrangements. Each speaker unit has the same power, current, and voltage delivered to it with both arrangements. Yet the cable loss patterns are different! The monowired case shows a ‘cross product’ term involving both signal frequencies which is absent when the system is bi-wired.

numbers time...

1. the amp injects the same power into each arrangements..

2. the speakers each get the same power.

3. the wires dissipate differently.

If one applies the first law of thermodynamics to these sentences, the conclusion is, all three of these together violate the first law. So, what is amiss?

My prediction is that jim will produce at leasts two more new and improved pages to debunk my analysis. Alas, the next one will conflict with his sentence:

As a result, the two behaviours cancel out, and the two arrangements behave identically so far as the amplifier and speaker units are concerned. Thus if out interest is in comparing the arrangements for the task of conveying signals from the amplifier to the speaker units, then they are indistinguishable. The ‘internal’ details differ in terms of how energy is stored or dissipated, but this has no consequence so far as using the system is concerned.

Interesting that the energy that is stored in the speaker does so differently in each case, yet the drivers which are connected in series with each energy storage device (which somehow stores different amounts of energy)....are immune to this difference..

hmm.

Key word to consider: Phase.

AH: I do enjoy this avenue of dialogue..thank you for continuing it. It is a wonderful way to invoke thinking..

Cheers, John

 

[jneutron]

And now, for a conundrum which is of far more interest...

Jim has confirmed that the losses within the wire, specifically the differences in loss between bi and mono, are exactly as I stated they are.

Now, let's look at the monowire case only..in more detail..

Let's measure the power that is travelling through the wire.

The first point is, the current along the wire from the amp to the speaker is the same through the entire wire. I'm sure we can all agree on that..(for this discussion, we ignore any energy storage in the wire, L and C..)

Now, at the amp, there is a voltage at the terminals. This voltage, when multiplied by the current at the terminals, produces the exact power that is flowing through that spot.

Now, lets go halfway towards the speaker. We know the current at that point, as it is the same throughout the wire.. Now, what is the power at that point? It is the power at the amp minus the power that was lost between the amp and the midpoint. So, if you subtract the power lost in the wire from the amp power from the first measurement, you end up with a different power that is continuing on towards the load..note that we include "negative power", which both Jim and I concur.

So, take that "different" power, and divide it by the current common to the entire wire, and what is the voltage going to look like?

Repeat this at the speaker terminals..consider the speaker as a black box, a plane in space where power is delivered to..

The power at the terminals will be the amp power minus the wire loss. And as Jim pointed out, that wire loss is different for the monowire case..

With the power envelope at the speaker terminals being different from that at the amp, but yet with the exact same current, what will the voltage at the speaker terminal be, V = P/I...for all instants in time?

If you believe Jim's confirmation of my dissipation modulation analysis, that voltage cannot be the same as that which is at the amp...specifically, it cannot be exactly proportional to that of the amp, because the difference is not exactly proportional to the amp's delivered power, but contains a product term of the two frequencies.

Now....


Why is it that difference has not been measured? Either it is there, as the dissipation difference requires it be...and not measureable using standard techniques, or it is not there and there is no difference in wire powerloss..(which Jim now agrees with me there is).

The real conundrum...

Note that this aspect does not require anything said about the filters within the speaker...it does not care..I do not have to prove his assertion of "filter compensating for resistive loss" incorrect, this is just the wires outside.

Cheers, John

 

[PENG]

Mr. Neutron, I quickly glanced through that long thread about why bi-wiring makes no sense (something like that) as well as Jim's article and I don't recall seeing any comments about some speaker manufacturers claim of the effect of the back emf created by the woofer in the case of mono wire. I don't know how significant such effect can be and whether it is audible. To me, it seems like a technically sound argument that such effects exist, according to physics/electrical theories. Please offer your comments on this if you don't mind. Thank you in advance

 

[PENG]

I quote part of a response from someone (admin: please delete it if I am not supposed to do this, thanks)

"People tend to measure the voltage at both ends of the cable. Because the cable has a finite impedance and the voltage is held linear at the amplifier end, you must see a non-linear voltage at the speaker end. People then interpret this as distortion induced by the cable, when in fact it is induced by the driver. But it also alters the voltage seen by the other drivers in a multi-driver system if only one cable is used. Is it important. Probably not that much. "

Neither Part1 nor Part2 addressed such a claim. I think most people, myself included, feel that any audible difference resulting from bi-wiring is either undetectable by human or simply not real, but I have not seen any analysis so far that proves it one way or another. Most attempt to do so seem (to me anyway) to have a preconceived notion that there is no difference to the amp and the speakers regardless of audible or not; and then proceed with their analysis making assumptions that do not cover all the contributing factors in order to simply the mathematical part of the analysis.

IMHO, failing to include the effect of the claimed back e.m.f. generated by the woofer is just one example. Not considering the inductive behaviour of the cable is another. Ignoring the inductive/capacitive effects eliminate the need to perform complex calculations involving complex numbers, Laplace transforms, Fourier transforms etc., but then how can you use a much simplified model to draw a conclusion, without first proving the complex part of the analysis is not relevant in the first place.

That being said, I do appreciate, and have great respect for the writer, who took the time to show us his calculations after stating his assumptions clearly in the beginning. This is a much more credible analysis, compared to (really no comparison) people who simply made general statements and tried to back them up with nothing more than Ohm's law and a few power formula, while not applying those formula correctly in their perceived circuit configurations.

 

[jneutron]

Neither Part1 nor Part2 addressed such a claim.

Part 1 was written solely to debunk any assertion of dissipation modulation, the 2AB product. He used an incorrect model, one without any branches, so showed zero 2AB product. He neglected the fact that I stated a no branch system does not contain the 2AB product. His part 1, therefore, serves no useful purpose, as his part 2 indeed confirms what I stated all along, that the reactive branches do indeed force a 2AB product of dissipation which is non-existant in biwiring...this is indeed a difference.

IMHO, failing to include the effect of the claimed back e.m.f. generated by the woofer is just one example. Not considering the inductive behaviour of the cable is another.

I limited discussion to pure resistive loads with the simplest crossover possible to keep the analysis simple. This also includes ignoring for now, the cable energy storage. Back EMF also makes it difficult to analyze, so is also not included. Look at his discussion when only resistive losses are in the mix.. First, it's not there, then it's there but the amp and filter compensate exactly for the wire dissipation loss ..

He also did exactly what I did, used two frequencies that are far too close for reactive branching, for the purpose of clear explanations and graphs.

I cannot fault him for not including the other aspects of the problem. We both seem to agree it is best to work on the simple stuff first.. It is how I partitioned the problem that he does not understand, so he tries to fit it to the classical analysis. I believe his choice of tool to be inadequate to address what I speak of, as his tools simply do not address conservation of energy.

I do not live or die on the end result of this analysis...I have no financial stake. It is up for all to see and understand, and if it ends up as incorrect, so be it. However, non peer reviewed debunking, with erroneous assumptions do not float my boat. If my analysis is to be proven incorrect, it will require accurate assumptions and concepts to do so.

Cheers, John

 

[gene]

Mr. Neutron, I quickly glanced through that long thread about why bi-wiring makes no sense (something like that) as well as Jim's article and I don't recall seeing any comments about some speaker manufacturers claim of the effect of the back emf created by the woofer in the case of mono wire. I don't know how significant such effect can be and whether it is audible. To me, it seems like a technically sound argument that such effects exist, according to physics/electrical theories. Please offer your comments on this if you don't mind. Thank you in advance

It's a bogus argument since the amplifier itself has to deal with the back EMF of the drivers anyways. Thus one of many reasons why amplifiers employ feedback. Jim's analysis is right on and aside from a slight change of cable impedance, biwiring makes little to no difference. Star Trek physics need NOT be used here and so FAR nobody has made a convincing argument FOR bi-wiring.

 

[jneutron]

It's a bogus argument since the amplifier itself has to deal with the back EMF of the drivers anyways. Thus one of many reasons why amplifiers employ feedback.

The intial assumption is that the amplifier is a voltage source, therefore the amp node voltage is unconcerned with the current draw from it's terminals. Mention of feedback in this context is irrelevant.

Jim's analysis is right on and aside from a slight change of cable impedance, biwiring makes little to no difference. Star Trek physics need NOT be used here and so FAR nobody has made a convincing argument FOR bi-wiring.

Star trek physics has not been invoked. I have used nothing beyond either high school physics nor high school algebra.

Jims analysis: hmm..

.....dissipation patterns differ – can now be seen in terms of the way the filter networks temporarily store and release energy as a consequence of their defined properties. No energy is mysteriously ‘lost’ or created out of nothing. All that is happening is that, as is usual with circuit elements with frequency dependent behaviour, some energy storage and release is involved.

So, the filter networks "temporarily store and release energy".. this is nature of the beast.. What he says is that they somehow compensate for the different wire dissipations which occur in bi vs monowire.. they do indeed compensate in an RMS average fashion, but they are rate of change beasts, not as the negative resistance implied by his statement.

The filter compensates? How? The "filters" are actually an inductor or capacitor in series with it's driver. Any change to how the filter stores and releases energy has to come through the driver..

And I am not arguing, nor trying to convince anybody to biwire. I am showing how it differs from monowiring in it's treatment of time dependent energy loss within the wire.

Simple math, simple concept.

Oh, and this gem:

No energy is mysteriously ‘lost’ or created out of nothing.

I've not stated such. Why does he feel the need to fabricate silly statements of this nature??

Cheers, John

 

[Resident Loser]

Geez...

...And I am not arguing, nor trying to convince anybody to biwire. I am showing how it differs from monowiring in it's treatment of time dependent energy loss within the wire...

...wasn't that misconception settled a while back?

I'm a nitwit dummy and I got it...

jimHJJ(...less math and more reading comprehension seems required...)

 

[jneutron]

...wasn't that misconception settled a while back?

I'm a nitwit dummy and I got it...

jimHJJ(...less math and more reading comprehension seems required...)

One would think so. I mean, even Jim posted the dissipation modulation losses of the wire in his debunk rev 2.0, contrary to his rev 1.0 stance...But alas, now the crossover compensates for the wires..

Sigh.

Just got back from a hospital in Prov RI...man that place is a changin so much over the years..

Cheers, John

ps..arrrrrgh, I hate this 60 minute edit feature..

It's a bogus argument since the amplifier itself has to deal with the back EMF of the drivers anyways. Thus one of many reasons why amplifiers employ feedback.

Upon re-read, I concur with Gene..this is bogus in that it is a confounder, primarily used by "white paper writers" to further muddy the waters, and make them sound like they know what they're talking about.

My comment was in the context of my biwiring analysis, so was completely off the mark w/r to Gene's statement..sorry bout that gene..

Cheers, John

 

[Roger K]

Bi Wiring Comparison

The bi-wiring scheme that is wired discreetly to HF and LF sections potentially has more insertion loss to the woofer because the LF section contains more of the typical music spectrum (power-wise) but must recieve it through double the impedance vs if the cables are connected at both ends.

 

[caper26]

I didn't read through all the nause, and was unable to open and look at the circuit diagram, but I am assuming that the diagram doesn't go back far enough inside the receiver to account for the distance from the actual AMP circuit to where the cable is EVENTUALLY split into 2, whether that be near the amp terminals or the speaker terminals.... if you have sufficient gauge wire (mono) then bi wiring makes no sense. If you want experiment with the minimum gauge wire possible for mono/bi-wire, then I think it might...if the run was sufficiently long. my 2 cents.