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speaker cable, why is it never twisted
Speedskater
post Nov 8 2012, 18:18
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Some "Good Engineering Practices" can not be ABX tested. When Mr. Brown's papers or Mr. Ott's book write about ways to reduce susceptibility to EMI/RFI no test can be performed that covers all conditions. You would first have to have a system that is being interfered with (or is your system interfering with something else?) before starting the test. But the possible causes, the possible cures and the possible system configurations is limitless, so our ABX tests will go on forever.


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pdq
post Nov 8 2012, 18:18
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QUOTE (mzil @ Nov 8 2012, 10:38) *
For the musical selection I'd try dead silence with lots of gain, or if that's "not allowed" I'd try some notably quiet passage.

Changing the gain will have no effect on speaker wires. In fact, perhaps the way to test is with the amplifier turned off. Otherwise you could be detecting noise pickup before the amplifier.
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greynol
post Nov 8 2012, 18:21
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@mzil:
Do you mean similar to cranking the volume well past normal loud listening levels just to hear fade-outs?
I think that's cheating, though running the amplifier without feeding it content is perfectly OK in my book.

@all:
Would there be anything wrong with recording the output of an amplifier at the speaker terminals with either a load box or with the speakers connected?

@pdq:
Providing two samples, one with twisted cable and one without should suffice, right?

This post has been edited by greynol: Nov 8 2012, 18:25


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greynol
post Nov 8 2012, 18:24
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QUOTE (Speedskater @ Nov 8 2012, 09:18) *
Some "Good Engineering Practices" can not be ABX tested. When Mr. Brown's papers or Mr. Ott's book write about ways to reduce susceptibility to EMI/RFI no test can be performed that covers all conditions. You would first have to have a system that is being interfered with (or is your system interfering with something else?) before starting the test. But the possible causes, the possible cures and the possible system configurations is limitless, so our ABX tests will go on forever.

That is the usual cop-out which gets rejected time and again on this forum.

If you wish to make claims you need to provide proof. The burden is not on me to prove that such claims could never be right.

This post has been edited by greynol: Nov 8 2012, 18:30


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Speedskater
post Nov 8 2012, 18:26
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QUOTE (pdq @ Nov 8 2012, 12:18) *
QUOTE (mzil @ Nov 8 2012, 10:38) *
For the musical selection I'd try dead silence with lots of gain, or if that's "not allowed" I'd try some notably quiet passage.

Changing the gain will have no effect on speaker wires. In fact, perhaps the way to test is with the amplifier turned off. Otherwise you could be detecting noise pickup before the amplifier.


It would be good to read at lest the first few pages of Mr. Brown's paper. (the middle sections of the paper are directed to HAM's and their problems)

What is happening is the interference entries the amp via the speaker wires, then sneaks back to the input stage though the negative feedback network and gets demodulated and amplified.
Mr. Brown explains it much better than that.


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pdq
post Nov 8 2012, 18:43
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QUOTE (greynol @ Nov 8 2012, 12:21) *
@all:
Would there be anything wrong with recording the output of an amplifier at the speaker terminals with either a load box or with the speakers connected?

You need to be very careful how you record this. A speaker has perfect normal mode rejection so your recording device would need to be as near perfect as you can get to be valid.

OTOH, a speaker does not respond audibly to very small voltages, so the recording device does not need to be very sensitive.
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Speedskater
post Nov 8 2012, 18:45
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QUOTE (greynol @ Nov 8 2012, 12:24) *
QUOTE (Speedskater @ Nov 8 2012, 09:18) *
Some "Good Engineering Practices" can not be ABX tested. When Mr. Brown's papers or Mr. Ott's book write about ways to reduce susceptibility to EMI/RFI no test can be performed that covers all conditions. You would first have to have a system that is being interfered with (or is your system interfering with something else?) before starting the test. But the possible causes, the possible cures and the possible system configurations is limitless, so our ABX tests will go on forever.

That is the usual cop-out which gets rejected time and again on this forum.

If you wish to make claims you need to provide proof. The burden is not on me to prove that such claims could never be right.


Well I did not make any claims! I posts short excerpts from the papers of leading experts/authorities in the EMC field. Mr. Ott's 850 page text book is used in all fields of electronics. Mr. Brown's some 50 papers cover many tests and experiments. I don't think that I could deconstruct how they arrived at those statements.


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pdq
post Nov 8 2012, 18:49
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QUOTE (Speedskater @ Nov 8 2012, 12:26) *
What is happening is the interference entries the amp via the speaker wires, then sneaks back to the input stage though the negative feedback network and gets demodulated and amplified.
Mr. Brown explains it much better than that.

I did, in fact, have an experience many years ago in which a neighbor's HAM radio transmitter interfered with my tape recorder (just for a day or two). My understanding at that time (and I had many friends who were HAM radio operators) was that this was probably less of an issue with the tape recorder than that the transmitter was not operating properly. In any case I only experienced it that one time.
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greynol
post Nov 8 2012, 18:58
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How about mic-ing the speaker then?

This really need not be complex.

AFAIC defending twisting conductor pairs is no different than defending brands of speaker wire.


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mzil
post Nov 8 2012, 21:06
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QUOTE (greynol @ Nov 8 2012, 13:21) *
@mzil:
Do you mean similar to cranking the volume well past normal loud listening levels just to hear fade-outs?
I think that's cheating, though running the amplifier without feeding it content is perfectly OK in my book.

What I meant is the noise may be very faint. It could easily be masked by compressed rock music or any music without quiet sections.

Unfortunately it may also be easily masked by background, ambient living room noises such as AC, refrigerator, hard drives, cooling fans, furnace, lamp ballast noise, wind, distant traffic/aircraft, birds/crickets, etc.

Better than "turning up the volume knob" would be to sit right next to the speaker with your ear next to it during a quiet passage (or silence if that's allowed). This would allow you to more easily hear a faint added noise either because:

A. "the interference entries the amp via the speaker wires, then sneaks back to the input stage though the negative feedback network and gets demodulated and amplified" as Speedskater mentioned Mr Brown put it.

or

B. It has nothing to do with the amp. [If indeed the faint noise enters the speaker wire and goes straight to the speaker, you will hear it most easily by this method. Very efficient speakers would be best to use for this.]

I'd also like to point out that it should be done with a full range speaker and not a compact monitor. The noise I suspect would be an issue, AC hum, will be at 50 or 60 Hz, which is below the capability of many small speakers. [And obviously if using a modern day AVR it would be important to disengage "bass management" so the main speakers get the full range. No subwoofer should be used.]

I don't own an ABX comparator box nor do I have an environment with a low NR (noise rating), so count me out.
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greynol
post Nov 8 2012, 21:11
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If it is so faint as to be undetectable other than through extraordinary means, it begs the question as to whether it is really necessary.


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Arnold B. Kruege...
post Nov 8 2012, 21:22
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QUOTE (john11 @ Nov 7 2012, 02:31) *
I have owned quite a few different speaker cables in my time and have always noticed the copper strands of wire within the cable run straight and parallel to each other I.e. they are not twisted. In fact the same is true of mains cable.


You need to get out more. ;-)

Most consumer grade speaker wire I see is indeed composed of parallel conductors as you say. However most speaker wire that is intended for professional use including permanent installation in homes is twisted.

The reasons for this have nothing to do with sound quality.

Twisting and jacketing cables makes it round and easier to install permanently or temporarily.

Twisting cable also decreases its length - the harder you twist it the shorter it gets. So twisting speaker cable increases its resistance per foot slightly, and also makes it a little more expensive to produce.


QUOTE
Can anyone tell me why this is I was told the electricity has trouble flowing through twisted strands, if each strand was enameled you might get an inductance effect but obviously it is not so the electricity should take the straightest path, so if the strands are twisted or not should have no overall effect.


Whoever told you this is poorly informed.

Twisting speaker cable significantly reduces its self-inductance which can actually build up over long lengths to cause a slight dulling of the highs when the speaker has very low a impedance at high frequencies. So twisting wire can have the opposite effect that was claimed by the person you consulted with.

Neither of the above situations apply to most speaker cables in home audio systems so twisting generally has no effect on reliably audible sound quality.

If speaker cables had high impedance source and load and carried small signals we could get worried about noise pickup which is also reduced by twisting. But speaker cables have low impedance sources and loads and carry relatively large signals, so again twisting has no significant audible effect in almost all situations.

For the record a passive loudspeaker responds only to the difference of the voltage on its input leads and thus has inherent resistance to common-mode interference. So if it wasn't for the conditions stated in the previous paragraph, twisting could be a good idea for SQ reasons.

QUOTE
Can anyone tell me why the copper strands are never twisted.


Hard to do because it is simply not true. ;-)

Here are some examples of twisted and untwisted speaker cable:

http://www.markertek.com/Cables/Bulk-Wire-...able-Bulk.xhtml

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Arnold B. Kruege...
post Nov 8 2012, 21:26
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QUOTE (Speedskater @ Nov 7 2012, 09:46) *
Really all cables be they power, signal interconnects or speaker should be twisted! (save for co-ax)

Jim Brown writes:

Twisting Cable pairs are twisted together for two very important reasons. First, bringing them
more tightly together reduces the coupling of external magnetic fields (while increasing the
coupling between the conductors) by reducing the loop area between them. Second, twisting
them together in a very symmetrical fashion causes any noise coupled onto one conductor to
be more perfectly cancelled (in the receiver) by noise coupled onto the other conductor.
Twisting reduces both magnetic (inductive) and electric (capacitive) coupling.
To understand how twisting does this, consider a magnetic field from a source that is closer to
one side of the cable than the other. At any point along the cable, one conductor will be
closer to the source than the other, so the induced voltage will be greater in that conductor
than in the other. But one half twist along the cable in each direction, the other conductor
will be closer to the source, and so will have the greater induced voltage, but the polarity will
be opposite. The more symmetrical the twisting, and the "tighter" the twisting, the more perfectly
the two induced voltages will match each other over the length of the cable, and thus
be better cancelled by the receiver. The number of twists per unit length is called the "lay" of
the cable.
Twisting also reduces capacitive coupling onto the cable, and for the same reasons. The ability
of twisting to reduce coupling extends to very high frequencies. Ethernet networks run on
high quality, unshielded, twisted pairs at frequencies in the hundreds of MHz, and require
good crosstalk rejection to function well.


Cables, Transmission Lines, and Shielding for Audio and Video Systems
by Jim Brown - Audio Systems Group, Inc.
http://audiosystemsgroup.com

http://audiosystemsgroup.com/TransLines.pdf



The above issues can be relevant when the signals are small and the impedances are high.

Speakers always have low impedances and always handle among the highest voltages anyplace in an audio system.

So, twisting speaker wires generally has no audible effect.

This post has been edited by Arnold B. Krueger: Nov 8 2012, 21:34
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Arnold B. Kruege...
post Nov 8 2012, 21:33
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QUOTE (Speedskater @ Nov 7 2012, 21:51) *
From page 2 of the above paper:

Output Wiring is Important Too! It is well known, for example, that RF interference is often coupled
into the output stage of audio equipment for example, the power amplifiers that feed loudspeakers
or headphones. There is always feedback around that output stage, so RF present at the
output will follow the feedback network to the input of a gain stage, where it will be detected and
amplified.


The above could possibly be true in a situation like near a high-powered radio transmitter. I've seen some crazy stuff happen in radio stations that had their transmitters in the same room that their announcers worked in. It was probable that a radio station in this dire of a circumstance had some errr, expedient engineering.

Back in a typical residential situation, it doesn't happen.
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mzil
post Nov 8 2012, 21:50
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Mr. Krueger, out of curiosity, do you own an ABX comparator box as I suspected earlier?
---

In-wall NEC CL2/3 rated speaker wire is always twisted pairs, at least that I've come across, so I tried to find if that's a stipulation in NEC Article 640, 400, or 725, but my Google powers faded on me so I gave up. [I provide that link in case anyone else wants to run with it.]

Another reason an in-wall wire might be twisted is it then can be encapsulated with another plastic sheath and the circular cross section then becomes easier to fish through holes without getting snagged.

@greynol, I take it you are considering the possibility of recording two segments by tapping the signal at the speaker terminals to then use fb2k ABX, right? [Yes, do that. Don't use a mic.] But my question is how do you time align the two recordings during the playback test? Manually? Restarting from the beginning still may have a "tell", a giveaway, in that the listener would be subconsciously picking up on the different delays before the music starts.

This post has been edited by mzil: Nov 8 2012, 22:08
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greynol
post Nov 8 2012, 22:11
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Again, it it is that faint or subtle it begs the question as to whether it is necessary.


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pdq
post Nov 8 2012, 22:20
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QUOTE (mzil @ Nov 8 2012, 15:50) *
But my question is how do you time align the two recordings during the playback test? Manually? Restarting from the beginning still may have a "tell", a giveaway, in that the listener would be subconsciously picking up on the different delays before the music starts.

I don't think that anyone is suggesting an effect for which music needs to be playing. To ABX silence vs. silence does not require time aligning.
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mzil
post Nov 8 2012, 22:35
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^ Some consider silence as a test signal "cheating". For instance, using silence alone will almost always find at least a small difference between the noise floors of things like CD players, preamps, power amps, etc., at least if one is allowed to listen to the residual noise floors and they differ by 1 dB or more.
---

A noise problem which is , oh let's say as a random example, -80 dBFS may not be an issue for some people, in some environments, with some music , but very much of a problem for other people with other music in other environments. I for one would like to know more about what kind of levels we are talking about, if it even is a problem at all, which I never claimed it was.

The problem is also 100% dependent on some noise generator being present, which may only be the case in some of our rooms. Having "no problem at all" now doesn't mean adding, say, a light dimmer in one's wall won't be a big problem a year from now, all because one concluded, "UTP in-wall speaker wire is for the voodoo believing nuts and costs more. I'm going to save money and buy the parallel runs instead".

This post has been edited by mzil: Nov 8 2012, 23:14
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pdq
post Nov 8 2012, 22:45
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There are lots of places in the home audio system where it is conceivable that an external source of noise can become audible. Places where the signal consists of microvolts to millivolts at high impedance levels will always present a potential problem.

However, if you install a dimmer and suddenly you hear a buzzing in your speakers, the speaker wires are the last place to look for a solution. Even expensive line cords are more likely to have a positive effect (and I for one do not advocate expensive line cords).
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greynol
post Nov 8 2012, 22:57
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QUOTE (mzil @ Nov 8 2012, 13:35) *
^ Some consider silence as a test signal "cheating".

In the event that you used a caret to refer to a previous post, no one claimed using silence as a test signal was cheating.

Rather, it was cranking the volume beyond what you would ever use for listening to real content that was suggested (by me) as cheating.

QUOTE
Having "no problem at all" now doesn't mean adding a light dimmer in one's wall won't be a big problem a year from now, all because one concluded, "UTP in-wall speaker wire is for the voodoo believing nuts and costs more. I'm going to save money and buy the parallel runs instead".

True, but I find tangible evidence for doing something far more compelling than basing decisions on what I can only describe as fear and paranoia, personally.

EDIT:
In retrospect, I suppose there's nothing wrong with "playing it safe". Clearly how far one ought to go is a subjective call.

This post has been edited by greynol: Nov 8 2012, 23:11


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splice
post Nov 8 2012, 23:31
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QUOTE (Arnold B. Krueger @ Nov 8 2012, 13:33) *
The above could possibly be true in a situation like near a high-powered radio transmitter. I've seen some crazy stuff happen in radio stations that had their transmitters in the same room that their announcers worked in. It was probable that a radio station in this dire of a circumstance had some errr, expedient engineering.

Back in a typical residential situation, it doesn't happen.


It can happen in a non-typical situation. At one time I lived in a house that was almost under the antenna of a 2 KW AM broadcast transmitter. It was an inverted L run between 2 towers. It was so close that the wire fell across the house roof one day when it broke at the far end. One set of speaker wires ran under the house to the next room. The leads were twisted, but still injected enough RF to be audible when the phono inputs of the amp were in use. I had to wind about 20 turns of the speaker leads through a large toroid to eliminate it. (The RF field was quite strong, if I hovered the palms of my hands just above the keyboard of my PC it would type random characters..)


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mzil
post Nov 8 2012, 23:35
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QUOTE (greynol @ Nov 8 2012, 17:57) *
QUOTE (mzil @ Nov 8 2012, 13:35) *
^ Some consider silence as a test signal "cheating".

In the event that you used a caret to refer to a previous post, no one claimed using silence as a test signal was cheating.

Rather, it was cranking the volume beyond what you would ever use for listening to real content that was suggested (by me) as cheating.

I used the caret to mean the post immediately above mine. I'm not very up on forum communication protocols so please feel free to correct my use of that. Did I use it incorrectly?

I didn't mean it had been implied earlier in the thread as being "cheating", I was trying to convey that my experience has been that some people I meet consider the use of silence to be unacceptable and verboten, and I didn't know the policy here. I will try to remember that here it is acceptable with the provision you stated of no artificially loud cranking of the volume knob. Got it.

This post has been edited by mzil: Nov 8 2012, 23:48
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greynol
post Nov 8 2012, 23:55
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It's all good. I only wanted to make sure I wasn't misunderstood.

My opinion on what is fair and what is not is in no way "official". I'm really just interested in getting to the bottom to whether we're talking audibility or just an opinion on best-practice.

This post has been edited by greynol: Nov 9 2012, 00:28


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aidenn0
post Nov 9 2012, 00:30
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I have personally been able to pickup an AM radio station on the speaker cables. At the time, I was living very close to an AM broadcast tower. It was only for very quiet sources that I had the problem (since I had the volume turned way up). I thought for sure that it had to be coming from before the power stage, but the reception varied when moving the speaker cables, and twisting the cables eliminated it.

This was with an RCA amplifier from the late 80s, there may have been something defective in its design; it seem does seem at least theoretically possible that any negative feedback amplifier could do something like this.
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DVDdoug
post Nov 9 2012, 02:05
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QUOTE (splice @ Nov 8 2012, 14:31) *
It can happen in a non-typical situation. At one time I lived in a house that was almost under the antenna of a 2 KW AM broadcast transmitter...

...I had to wind about 20 turns of the speaker leads through a large toroid to eliminate it. (The RF field was quite strong, if I hovered the palms of my hands just above the keyboard of my PC it would type random characters..)
That makes a good point... In extraordinary circumstances, you might need to take extraordinary measures. But, there is no reason for 99.99% of us to wrap our speaker wires around a toroid (or to twist our speaker wires). wink.gif In fact, somone with a similar problem/symptom might require an entierly different solution.

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