Cable differences: a simple experiment

awsmone · Mar 3, 2016

I have been pondering audio experiments to clear some light on some controversies

although whether one cable is "better" than another is a qualitative issue

whether they are different is another matter

The "null" hypothesis is they are no different

Thus the first step is to demonstrate is there is any difference

As with the recent detection of Gravitational waves: demonstrating "loss of cancellation" of two 'waves' is a simple way of demonstrating if differences exist

In my experiment: to audio signals identical but out of phase 180 would be run down opposing cables and then combined

In the null hypothesis they should cancel each other.

As in reality the inversion process is probably imperfect, the cables could be reversed and the differences themselves matched out of phase

I have read someone doing this in the digital domain

I would appreciate if anyone has read of this being done with analog signals

Regards

Andrew

Whatmore · Mar 3, 2016

Cancellation (or loss thereof) is good enough for the top physicists in the world, but we all know that audiophiles know better.

RayDunzl · Mar 3, 2016

I thought about your test for a minute.

When I got to "I would appreciate if anyone has read of this being done with analog signals" I realized that I have done this with speakers.

The result is far from null, which, this time, made me go "Hmmm..."

awsmone · Mar 3, 2016

RayDunzl said:
I thought about your test for a minute.

When I got to "I would appreciate if anyone has read of this being done with analog signals" I realized that I have done this with speakers.

The result is far from null, which, this time, made me go "Hmmm..."

Unfortunately, speakers are far too inaccurate for such an experiment in general, due to differences between each speaker, you would be measuring the difference between the right and left speaker. HFN publish right left speaker differences and even anechoic they vary a lot, in a room even more

I am not forming a view on what such an experiment will show, just its the first step in understanding whats going on.....

GaryProtein · Mar 3, 2016

RayDunzl said:
I thought about your test for a minute.

When I got to "I would appreciate if anyone has read of this being done with analog signals" I realized that I have done this with speakers.

The result is far from null, which, this time, made me go "Hmmm..."

Do you mean you connected the speakers to the amplifiers out of phase. . . and then listened to them?

You will get lower frequency note cancellation, but in the room, the overall sound is far from cancelled out.

That will give a very different result from watching two out of phase signals combine or cancel on an oscilloscope.

RayDunzl · Mar 3, 2016

It's just that I hadn't thought about about the act of setting speakers out of phase in this way before.

It occurs to me the direct sound should disappear, and leave only the less well-behaved reflections.

I do understand the Post 1 proposal.

---

I think I'll make some out-of-phase in-room stereo speaker tests for grins.

RBFC · Mar 3, 2016

I have 6 "identical" speakers (GoldenEar Triton 1) in my theater. Besides the obvious bass differences due to room placement, there are also small, but noticeable differences in upper frequencies as well. Some of this may be due to quality control, but I suspect it's more due to position.

A tactic often employed to adjust subwoofer phase to match the speaker it supports is via use of inversion/cancellation, where a test tone at the crossover frequency is played and the speaker +/- wiring reversed. Perfect adjustment of the subwoofer phase theoretically leaves dead silence (perfect inversion/cancellation), but rarely happens in reality.

The test with wires alone certainly poses less obstacles....

Lee

amirm · Mar 3, 2016

Seems like a clever new approach to testing cables for differences

. The trick would be the phase inverter. It would need to produce zero delay. And of course provide that perfect inversion.

Laser Interferometry works on principles of the two split beams becoming different and the resulting mixing/intermodulation of the two. It doesn't use cancellation of waves. If there is no difference between the waves they combine perfectly, if not, they combine based on theory of superposition. We can then work backward to extract what happened.

At waveform level cables will cause differences. I ran simulations showing phase shifts in cables which is a function of their electrical parameters. So they don't null out at the level that laser Interferometry is used.

Thinking out loud, you can use a scope and invert one of the channels and then sum the two. It should be easy enough test to run if there is interest.

DonH50 · Mar 3, 2016

A 'scope probably doesn't have the resolution for a null test on cables. Try a VNA.

amirm · Mar 3, 2016

Yeh, dynamic range is a problem.

GaryProtein · Mar 3, 2016

RBFC said:
I have 6 "identical" speakers (GoldenEar Triton 1) in my theater. Besides the obvious bass differences due to room placement, there are also small, but noticeable differences in upper frequencies as well. Some of this may be due to quality control, but I suspect it's more due to position.

A tactic often employed to adjust subwoofer phase to match the speaker it supports is via use of inversion/cancellation, where a test tone at the crossover frequency is played and the speaker +/- wiring reversed. Perfect adjustment of the subwoofer phase theoretically leaves dead silence (perfect inversion/cancellation), but rarely happens in reality.

The test with wires alone certainly poses less obstacles....

Lee

I'm sure most of the difference is due to some of the speakers being in different locations and your earlobes capturing different sounds in front, along side and behind you.

awsmone · Mar 3, 2016

amirm said:
Seems like a clever new approach to testing cables for differences . The trick would be the phase inverter. It would need to produce zero delay. And of course provide that perfect inversion.

Laser Interferometry works on principles of the two split beams becoming different and the resulting mixing/intermodulation of the two. It doesn't use cancellation of waves. If there is no difference between the waves they combine perfectly, if not, they combine based on theory of superposition. We can then work backward to extract what happened.

At waveform level cables will cause differences. I ran simulations showing phase shifts in cables which is a function of their electrical parameters. So they don't null out at the level that laser Interferometry is used.

Thinking out loud, you can use a scope and invert one of the channels and then sum the two. It should be easy enough test to run if there is interest.

Sorry I deliberately simplified the laser interferometry, though it does in some ways involve wave cancellation

I am not in the slightest suggesting there will be no difference

I think Amir it would be interested to see your modelling from electrical characteristics of cabling, especially if these were aligned with known real cable parameters

Then real tests could be run to see how close to modelling

This could then form the basis, of how these differences may influence perception

One of the frustrating aspect of many of the cable arguments is there seems little data to base any conclusions

As to dynamic range, this may be why the tester used digital analysis, as by multiple runs, you effectively increase dynamic range

Speedskater · Mar 4, 2016

Br covered a lot of this over a decade ago.
Cable Distortion and Dielectric Biasing Debunked

by Bruno Putzeys — August 29, 2004

http://www.audioholics.com/audio-video-cables/cable-distortion-and-dielectric-biasing-debunked
[url]http://www.audioholics.com/audio-video-cables/cable-distortion-and-dielectric-biasing-debunked/cable-distortion-and-dielectric-biasing-debunked-page-2
http://www.audioholics.com/audio-vi...c-biasing-debunked/cable-thd-measurements.pdf
http://www.audioholics.com/audio-vi...ng-debunked/additional-cable-measurements.pdf
[/URL]

still-one · Mar 4, 2016

With power cords we are just moving electrons, how do you cancel out an electron?

amirm · Mar 4, 2016

still-one said:
With power cords we are just moving electrons, how do you cancel out an electron?

You could resort to a technique like this:

still-one · Mar 4, 2016

amirm said:
You could resort to a technique like this:

After seeing that I won't be able to go for a week.

amirm · Mar 4, 2016

Speedskater said:
Br covered a lot of this over a decade ago.
Cable Distortion and Dielectric Biasing Debunked

by Bruno Putzeys — August 29, 2004

http://www.audioholics.com/audio-video-cables/cable-distortion-and-dielectric-biasing-debunked
[url]http://www.audioholics.com/audio-video-cables/cable-distortion-and-dielectric-biasing-debunked/cable-distortion-and-dielectric-biasing-debunked-page-2

Thanks Kevin. Looks like he performed OP's tests already:

"In-Out difference. Actually, two different cables of equal length were fed the above distortion test signals in opposite phase. The two outputs were summed through a trimmable network to null the output. Well, the output nulled completely (better than 120dB across the audio band)."

awsmone · Mar 4, 2016

Speedskater said:
Br covered a lot of this over a decade ago.
Cable Distortion and Dielectric Biasing Debunked

by Bruno Putzeys — August 29, 2004

http://www.audioholics.com/audio-video-cables/cable-distortion-and-dielectric-biasing-debunked
[url]http://www.audioholics.com/audio-video-cables/cable-distortion-and-dielectric-biasing-debunked/cable-distortion-and-dielectric-biasing-debunked-page-2
http://www.audioholics.com/audio-vi...c-biasing-debunked/cable-thd-measurements.pdf
http://www.audioholics.com/audio-vi...ng-debunked/additional-cable-measurements.pdf
[/URL]

Thanks Kevin

Great job finding it and Bruno of course

So....where does it leave us ?

Cable differences: a simple experiment

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