Cable directional benefit proven?

[juboy]

Just came across this whilst looking for a new SCART lead...

"NEWS #1 Oct '01

Press Release

SUPRA Cables First in World to Prove Directionality in Audio Cables

Supra Cables have taken part in pioneering measurements developed and conducted in a joint venture by Ben Duncan Research and Jenving Technology.

Directionality in audio cables has been controversial, particularly as no other cable maker in the world has previously been able to say what the mechanism is, let alone measure it.

Using regular lab equipment and test signals, the measurements show measurable, and repeatable quite large differences, when cables are reversed. The bottom line is the direction in which the wires inside were last 'drawn' at the copper factory. The tests even revealed conductors that had been reverse-spooled by the copper wire maker!

A proof of the forward thinking in Jenving's Supra Cables, the new test has been able to show that the conductors in all Supra production are not only already optimally 'directed', but that optimal directionality is also already correctly identified."

I know the news comes from a cable maker and in theory may be biased but I don't see what advantage/benefit they actually gain from saying a cable works better one way round than equally well either way round.

Also wondered what some forum members who say that cable directionality is a myth think about this.

 

[MikeK]

Chortle, chortle

The signal going down the cable is AC.
This means that current flows first one way and then the other.
If the cable is directional, then they are saying that the flow in one direction is impeded in some way - if so, then this is distorting the signal.

In essence, it's basically what a diode does - so if cable directionality exists, they are effectively saying that the signal is being rectified in one direction, but not the other, even if it's just a small amount.
It may be possible to construct such a cable (why would you want to though), even if it were by accident, but simply reversing the cable would mean that instead of the positive half of the waveform being affected, it would then be the negative.

Of course, they could have also discovered a way to prevent electricity in their cables obeying the normal laws of physics - ie the cable can be directional without distorting the waveform, and that AC in their cables doesn't actually really mean AC in the true sense of the word , ie current doesn't flow equally in one direction and then the other, as it does with every other form of AC current.

On the other hand, it could just be marketing bulls&*t!

 

[fastedd]

Originally posted by MikeK
Chortle, chortle

The signal going down the cable is AC.
This means that current flows first one way and then the other.
If the cable is directional, then they are saying that the flow in one direction is impeded in some way - if so, then this is distorting the signal.

In essence, it's basically what a diode does - so if cable directionality exists, they are effectively saying that the signal is being rectified in one direction, but not the other, even if it's just a small amount.
It may be possible to construct such a cable (why would you want to though), even if it were by accident, but simply reversing the cable would mean that instead of the positive half of the waveform being affected, it would then be the negative.

Of course, they could have also discovered a way to prevent electricity in their cables obeying the normal laws of physics - ie the cable can be directional without distorting the waveform, and that AC in their cables doesn't actually really mean AC in the true sense of the word , ie current doesn't flow equally in one direction and then the other, as it does with every other form of AC current.

On the other hand, it could just be marketing bulls&*t!

Dead right. Cables may be directional but the more they are the worse they would be. Otherwise we would end up floating the ac signal ontop of a DC level to keep the signal pure then stripping the DC off at the other end. OMG, maybe people do that sort of thing!!

Ideal transmission line theory needs balanced impedance in the source, transmission line and the load for the maximum power transfer. Ideally a cable needs to have a fixed impedance at all frequencies but thats never going to happen due to the small inherrent inductance and capacitance in the cables.

 

[buns]

If the signal is AC, directionality i imagine is a big problem. However, if the signal were dc (which i hazard to guess that many audio signals may well be) directionality is potentially useful. If you use some sort of anisotropic construction, you would be able to eliminate feedback down the cables if you had the reverse impedence very high.

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[fastedd]

Originally posted by buns
If the signal is AC, directionality i imagine is a big problem. However, if the signal were dc (which i hazard to guess that many audio signals may well be) directionality is potentially useful. If you use some sort of anisotropic construction, you would be able to eliminate feedback down the cables if you had the reverse impedence very high.

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All signals to conventional speakers are AC. Any DC component would offset the speaker outwards (or inwards depending upon the polarity) and would reduce the range the speaker could travel. Stick a large enough DC signal on long enough and you will burn out the speaker.

If you averaged a signal and it comes to zero it pure AC. If the average of the signal is either positive or negative then there is a DC component to the signal. DC does not mean a fixed constant voltage when talking about signals. This is the sort of thing that can happen when amps cook their capacitors, before you know it, burnt out speakers

 

[Dubbing Mixer]

Aaargh! Here we go again.

I don't pretend to understand the physics but speaker cables in particular let alone interconnects are not will not and never have been transmission lines in the accepted sense. As for directionality of cables, this makes about as much sense as a directional copper water pipe.

If you want the technical explanation check out John Watkinsons articles on the subject in (among others) Studio Sound and Resolution magazines.

PS I still connect my Van Damme cables following the arrows.......
superstitious I guess.