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Pano 2nd November 2006 12:22 AM

The JREF cable challenge test.
 
2 Attachment(s)
As you may know from reading the “Do speaker cables make a difference?” thread, I submitted a speaker cable test to the James Randi Educational Foundation (JREF).
JREF have put up a $1,000,000 prize for proof of the paranormal and have extended the challenge to include some audio cable claims.

The title of this thread is “The JREF cable challenge test.” But I will be calling my test the “Balanced Bridge Test” to be clearer about how it functions.

Below you can read what I submitted to JREF and their reply. The application allows only “two brief paragraphs” to state your claim. You will find those paragraphs below, as well as the diagrams I submitted. After the JREF reply, I will elaborate on the test, its strengths and weaknesses. All criticisms are welcome.

My submitted claim:

Quote:

Speaker Cable Test

This test will demonstrate that a real difference, both audible and measurable, exists between different types of speaker cables. This test is based on the well established bridge circuit (see below) that is very sensitive to differences in the two branches of the bridge. The illustrations below are the same electrical circuit. The key word to this test is “difference.” Thus only the difference between cables (if any) will be audible in the test speaker.

The demonstration will be conducted with real speakers, real amplifiers and a real musical signal, between non identical speaker wires. To be considered successful the demonstration will have to show an easily audible difference produced by the test speaker. The demonstration will be said to fail if no audible difference is found, or if the difference is one of simple attenuation that can be corrected with a volume control. The demonstration will also be considered to fail if the majority of the people listening determine that the audible difference is too small to matter.
The James Randi Educational Foundation reply:

Quote:

Your application for the JREF prize has been received today.

You claim that you can demonstrate a difference between the electrical characteristics of different sorts of speaker cables. This is evidently true, since small-gauge and/or cables of inferior materials or poorly connected, will clearly show less satisfactory audio images. We find nothing paranormal in that claim.

Your application is rejected because it does not fall within the parameters of the JREF challenge.
“Nothing paranormal” Can’t argue with that! But I think they missed the point. I claim to demonstrate the audible differences, not just electrical. And any test or audio signal can be used, even Elvis or ABBA.

The point is to conduct a rigorous test between what should be identical cables, same gauge and same length, with good connections, to find if there is a difference. Cables of different lengths and/or gauges could also be tested.

The test hinges on the difference. If there is one, then a signal will appear between the 2 sides of the balanced bridge. No difference, no signal. Pure and simple. Either there is, or there is not. Using a speaker or headphones across the bridge will allow the difference to be heard, if it exists. The difference could also be measured with voltmeter, oscilloscope, spectrum analyzer, etc. This is the Wheatstone Bridge, a circuit that has been used in measurements since the 1830’s.

Remember, -- all that is measured here is the difference, nothing else. That makes the difference very obvious, if it exists, because the difference is the only thing you will hear or measure.

Cables of different DCR will produce a difference signal in this test, but that can (or should) be ruled out.

If a difference is found, it will not tell you which cable is better. But by extension the test should be able to determine which cable is best, or at least which is of the “highest fidelity.” (More on that later)

There are, of course, difficulties in setting up the test and getting the bridge balanced using real loads, but those can be addressed. If the bridge is out of balance, you’ll know right away, that’s the beauty of the test. =)

I’ll go into more detail in the next post. Thanks for reading all the way down.

SY 2nd November 2006 12:40 AM

There's the flaw- you're not dealing with the claims of audibility which often (usually) venture over the paranormal line. No-one disputes that differences may be measurable with the right test setup (after all, they're just R, L, and C), the controversy surrounds claims of audibility between two systems that are not oscillating and have the same frequency response and level within the audio band.

soongsc 2nd November 2006 01:16 AM

I quite agree with SY.

macgyver10 2nd November 2006 03:36 AM

Hey Panomaniac,

I had to return to comment on this, since I was the one who brought up the JREF prize in the first place.

Your wheatstone application could, potentially, be used to help set up a JREF challenge, but it isn't essentially what the JREF is about.

In fact, it's not even what I was hoping to test either. As many have mentioned, there is no dispute that all cables have characteristic L,C,R values that define their electrical characteristics. There are even cases where these measurable characteristics can cause audible effects (ie, certain amp/load combinations or excessive capacitance cables causing oscillation in amplifiers.)

Engineers, and subjectivists both can agree on these points, and have.

What needs testing is the claims by some that electrially identical (in fact even "similar" would probably suffice) cables can cause audible differences that we can not measure using conventional L,C,R measurements.

For instance, if a OFC copper cable and a Silver cable were shown to have nearly the same values of L, C, R and were placed into a high DF amp/speaker combination, measurements would show them to essentially be identical. However, many "audiophiles" would maintain that the silver cable was far superior for a whole host of pseudoscientific reasons.

So, in a nutshell, if your JREF application where to say "I claim that, under controlled conditions, I can hear differences between speaker cables of different composition that show no measurable electrical differences." you might have a shot at the $1,000,000

So, unlike some have suggested, you haven't "won", because you haven't presented a paranormal (ie irrational) claim.

Pano 2nd November 2006 05:35 AM

Quote:

Originally posted by SY
There's the flaw- you're not dealing with the claims of audibility which often (usually) venture over the paranormal line.
Can't argue with that. But I'm not claiming paranormal properties for cables. And I don't know any cable seller who is. They may be claiming absurd things for their cables, but the claims are almost always based on science. Bad science, ridiculously bad science sometimes. But science and physics. No cables I've seen claim to be better because of witchcraft, voodoo, the Virgin Mary or space aliens. They claim to be better because of some physical properties of the cable.

So let's forget the paranormal stuff, OK?. That's why my claim was rejectedb y JREF, but it has nothing to do with the validity of balanced bridge test.


Quote:

No-one disputes that differences may be measurable with the right test setup (after all, they're just R, L, and C),
Ah, but some do dispute this. At least within "normal" boundaries. I agree that if the R, L and C are vastly different, there will be a noticeable difference in the sound. But many seem to claim that subtle differences in those values will NOT affect the sound.

Lets call them the "Zip Cord Club" (of which I my be a member). "14 gauge Zip Cord is all you need! Anything more is a waste of money! You won't hear a difference." OK, lets see if that is true. Let's test it. The balanced bridge is a good test.

On the one hand there are the cable enthusiasts who claim their cables are better because of better materials - pure copper, special insulation, long crystals, silver wire, etc. Or better because of special construction. Braids, ribbons, helium cores, cotton fibers, etc. And any mix of the above. The cable enthusiasts claim their cables sound better because of what these special qualities do - or don't do. If they are "better", then they are different.

An the other hand the Zip Cord Club claims that all that is nonsense, as long as the cable is of adequate gauge and is not causing amplifier oscillation, no one can hear the difference. Therefore NO difference in the audio domain.

But what if we test two different cables and do find a difference? Why is there a difference? Is it due to the different L, C, R values of the cables? We can test this. Simply add a few passive components to cable A, so that it matches the L C R of cable B. Test again. No difference? It must be the L C R values of the cable that give it its sound. No need to buy expensive cables if we can imitate the sound with a few passive components.

What if there is still a difference when the two cables have identical L C R values? Then we have to look further for what the difference might be.

The test is not limited to different cables. The same cables can be measured when they are deployed differently. For example, one cable run on the floor, the other on blocks. Is there a difference? You'll know for sure. Either there is or there isn't.

The strength of the balanced bridge test is that it removes the doubt as to whether a difference really exists. If you hear something in the bridge speaker, there is a difference. If you hear nothing, no difference. Simple as that.

EDIT:
Quote:

So, in a nutshell, if your JREF application where to say "I claim that, under controlled conditions, I can hear differences between speaker cables of different composition that show no measurable electrical differences." you might have a shot at the $1,000,000
Good point! And I can test for that. Don't know what the results will be, but it will be fun to find out.

macgyver10 2nd November 2006 06:00 AM

Quote:

Originally posted by panomaniac


Can't argue with that. But I'm not claiming paranormal properties for cables.

Neither is anybody else! The Paranormal ability is in the listener, not the cable.


Quote:

Originally posted by panomaniac

Good point! And I can test for that. Don't know what the results will be, but it will be fun to find out.


The only way to test for the claim that I proposed is double blind LISTENING tests. It's the only way to test the LISTENER that claims to hear what can't be measured.

One way to test the claim is to use two identical cables (use your wheatstone to make sure they are perfectly balanced if you like) but tell the claimant that one of them is cryogenically treated long crystal Silver foil, and the other is 14 guage copper lampcord.

Then tell him to make notes on the "sound" of each cable. Then test him in an ABX situation.

Guaranteed this listener will "hear" a difference when non exists, and not be able to tell the cables apart in a double blind ABX....

Cloth Ears 2nd November 2006 06:44 AM

Re: The JREF cable challenge test.
 
Quote:

Originally posted by panomaniac
The demonstration will be conducted with real speakers, real amplifiers and a real musical signal, between non identical speaker wires. To be considered successful the demonstration will have to show an easily audible difference produced by the test speaker. The demonstration will be said to fail if no audible difference is found, or if the difference is one of simple attenuation that can be corrected with a volume control. The demonstration will also be considered to fail if the majority of the people listening determine that the audible difference is too small to matter.
Hi Panomaniac,

You've only covered half of the conundrum. For the test to be valid, you also have to have comparisons between identical cables (ie the cable that the person is comparing is actually the same cable), giving the listener(s) the opportunity to "hear a difference" where there is no difference.

There are differences, Nelson Pass demonstrated this in 1980.

Pano 2nd November 2006 07:28 AM

Good points guys, but you've got to start thinking outside the ABX. Stop trying to fool the listener into hearing something that isn't there.

Part of the test setup will certainly have to be testing two identical cables in the balanced bridge to show that no difference can be heard, that the bridge is truly balanced. Only then can the test proceed to different cables.

Of course this doesn't eliminate the idiot who "thinks" he hears something when there is nothing. And I should know, I've been that idiot. We've all wanted to do well on a test, right? But if it can be shown on the O'scope, voltmeter, spectrum analyzer, etc., that there is no voltage difference, then the claim of hearing something can be debunked. If there isn't any current flow thru the bridge speaker, there won't be any sound. Simple.

And the test should be done with a number of people present. If the majority claim to hear nothing, then there is probably nothing there. And that can be confirmed with measurements.

In fact, the hearing part of the test is icing on the cake. It is only there to let you hear the difference that can be more easily measured. And there may be ultra or infrasonic differences measured, but if you can't hear them, why worry?

soongsc 2nd November 2006 10:33 AM

Quote:

Originally posted by panomaniac

...
And the test should be done with a number of people present. If the majority claim to hear nothing, then there is probably nothing there. And that can be confirmed with measurements.
...

It just means the majority claim to hear nothing. There still could be something. The same with looking for business opportunities. The majority don't see or react on it.

Quote:

Originally posted by panomaniac
In fact, the hearing part of the test is icing on the cake. It is only there to let you hear the difference that can be more easily measured. And there may be ultra or infrasonic differences measured, but if you can't hear them, why worry? [/B]
Good point.

SY 2nd November 2006 01:39 PM

Quote:

Of course this doesn't eliminate the idiot who "thinks" he hears something when there is nothing.
A point which cannot be stressed enough- hearing differences that are not there is not a result of idiocy, it's because we have human brains. Millions of years of evolution eliminated phenotypes that wouldn't react without 100% proof that there really was a sabertooth tiger outside the cave.

Our brains are wonderful at finding patterns, and will do so even when the pattern isn't there; running at the mistaken belief that there's a tiger carries very little evolutionary penalty. Not running causes one to be eaten and hence not reproduce. Perhaps this explains our fascination with abstract art and music, but that's going off topic...

Audiophiles want to hear a difference, so without proper controls, they will do so, difference or not. We're not test mikes, we're humans.


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