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Old 12-22-2006   #26
 
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Default Re: the science of cables

Quote:
Originally Posted by MIAaron
I don't know, the other night I was hanging out with my nephew and we found shape could have an impact on the sound. We had two mic's built of similar materials but in different shapes. With a GENUINE Dupont Micro-fiber interconnect we found a Campbell mic did provide descent results, but we preferred the more authoritative tone of the larger Progresso. How do you explain that with RLC?
are you taling about microphone shapes? That's not an electrical component, it's physical, which can affect the sound... like the shape of a speaker.
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Old 12-22-2006   #27
 
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Default Re: the science of cables

don't let that stop you.... I'm a ChemE working in environmental. Doesn't keep me from pretending I know what I'm talking about.
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Old 12-22-2006   #28
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Default Re: the science of cables

I apologize Thor, I failed to get my point across. Please dont read any more into my post as it was a bad joke. I gotta say you gave a good answer though, cuz in the context of my post physical traits are the only ones that matter.
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Old 12-22-2006   #29
 
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Default Re: the science of cables

Quote:
Originally Posted by Autiophile
You're right, this is a thread about the science of cables.
Were that actually the case, it would be nothing but blank posts.
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Old 12-22-2006   #30
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Default Re: the science of cables

Quote:
Originally Posted by MIAaron
I apologize Thor, I failed to get my point across. Please dont read any more into my post as it was a bad joke. I gotta say you gave a good answer though, cuz in the context of my post physical traits are the only ones that matter.

I got it..... but it took me a second of going.... Hu, um... Oh hell, he's pulling my leg

Chad

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Old 12-22-2006   #31
 
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Default Re: the science of cables

Quote:
Originally Posted by Thoraudio
there is something to be said for perception.
There is also something to be said for efficient allocation of resources. If people who obsess about wires channeled that energy and cash into fine-tuning Speaker placement by measurement and ear, optimizing their listening rooms, etc., the bottom line is that they would have objectively more accurate (not necessarily better-sounding, of course, but probably so) systems.

It's an upside-down hobby indeed when people whine about wires whilst listening to speakers that are so poorly engineered that their designers did not even bother to maintain smooth and relatively constant directivity over the midrange and treble.
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Old 12-22-2006   #32
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Default Re: the science of cables

Quote:
Originally Posted by chad
I got it..... but it took me a second of going.... Hu, um... Oh hell, he's pulling my leg

Chad
Is Mr. Sound Engineer baggin' on my Campbell mic? We had'em networked man, from one couch cushion fort to the next.
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Old 12-22-2006   #33
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Default Re: the science of cables

Man these threads always go the same way ... the only mystery in the realm of cables may just be, why i never seem to learn

But I will respond to the comments and questions posted by Wes

Yes, it's funny to me to think that the three (3) great mysteries of modern science are :

1. A unified field theory that accurately explains gravity, electromagnetism, strong & weak nuclear forces ... thereby unifying quantum mechanics and general relativity.

2. The existence of dark matter and dark energy, which seem to cause to rate of expansion of the universe to be increasing ... beyond all expectation.

3. How the hell to get a 20kHz electrical signal down a few feet of wire.

But anyway ... let's take a moment to address the question about how the cable may impact electrical, and therefore ultimately acoustic, phase. The first, and only, rule in "cable engineering" is : how do any claimed or advertised "properties" impact RLC? Resistance, Inductance and Capacitance are ALL you need to be concerned with (putting aside, for the moment, contact metallurgy and noise immunity). These well-established electrical properties are the "filter" (if i may) through which any crazy geometry or elixir claims should be passed. Why? Very simple : if something doesn't impact RLC, it won't impact the transmission of a 20kHz signal through a cable less than about a mile long. This is, unfortunately for some, not subject to opinion or experience. If your subjective experience suggests otherwise, you have been fooled (fret not, though, it happens all the time). Ignoring this simple fact, demonstrates a fundamental ignorance about electrical engineering and the work done by brilliant minds for centuries concerning electrical theory. RLC concepts have become SO powerful in modelling, explaining and predicting the universe around us, that they are also used in mechanical and acoustical sytems as well. Don't believe me? Too bad.

Once again ... I am NOT suggesting that all cables sound the same. That's an hypothesis that would be ridiculously easy to disprove. I am, however, suggesting ... or rather, stating as factual with the same confidence that the earth will continue to rotate tomorrow ... that any sonic differences are attributable to RLC analysis (contact metallurgy and noise immunity aside).

OK ... so let's look at an exaggerated, but not outside-the-realm-of-possibility, example. Say we've got an RCA cable with a (high) capacitance of 40pF per foot. And we are driving 50 feet of that cable from a (high) source impedance of 1kohm. Let's ignore any series resistance (R) in the cable (it will be much less than the 1kohm source), and we'll also put aside any series inductance (L) for now. We'll just concern ourselves with C. We'll also assume that the amplifier on the receiving end has a very high input impedance, much higher than the 1kohm source, so we can ignore that as well.

In this case, it's very easy to show that the source resistance and cable capacitance form a simple, first-order RC low-pass filter. This does NOT mean that anytime a resistor and capcitor are in a circuit, that a simple first order low-pass is formed. It is so in this case, because the source resitance is a series resistor and the cable capacitance is a shunt capacitor, and the output is observed across the shunt capacitor.

The cutoff or -3dB frequency of this low-pass filter is :

f3db = 1/(2*pi*R*C) = 1/(2pi*1kohm*40pf/ft*50ft) = 80kHz

Next post we'll show how an 80kHz low-pass filter impacts magnitude ... and phase ... of a 20kHz signal. What other "electrical properties" of the 20kHz signal might be impacted? That's simple : NONE. Why? Because there AREN'T any ... not in a linear system. And it's a no-brainer to consider a cable to be a linear system ... by far, wire is the most linear of electrical components we have to worry about in storing, transmitting and reproducing acoustical information.

What about time-domain properties like transient response? Isn't that something to worry about? Why yes it is (or may be) ... glad you asked But we've already got you covered ... completely, in fact. ANY and ALL time domain properties are UNIQUELY linked to frequency domain MAGNITUDE and PHASE. ALL time domain properties are uniquely and completely dependent on what happens in the frequency domain (considering both magnitude and phase). This means that ALL time domain behavior is 100% accurately predictable if you know the frequency domain behvior. And it also means that you can't have two circuits which behave identically in the frequency domain, but differently in the time domain. Never gonna happen ... it's been proven, with the certainty of a theorem ... and there is no stronger PROOF in all of human experience. Yeah ... it a was french dude who did it (Fourier), but he was right nonetheless
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Old 12-22-2006   #34
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Default Re: the science of cables

Excluding the connectors, if all of the properties of cables actually do have an affect on sound, wouldn't that mean that the internal amplifier wires and circuit board material would also have an affect on sound? Do amplifier manufacturers pay the same close attention to the materials they use as the cable manufacturers?

Or does the length of the cable affect the sound and that is why the materials used matter so much?

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Old 12-22-2006   #35
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Default Re: the science of cables

quick answer ... look how long the above cable had to be (and at a rather high capacitance per foot, too), in order to get a -3dB cutoff frequency as low as 80kHz

So, no ... amplifier manufacturers don't really need to worry about what type of wire they use except, of course, heavy enough gauge for the current and Power delivery.

They have other things to worry about, however. Stability concerns certainly force one to look into the several hundred kilohertz, or even megahertz range, for interesting signal dynamics, for example. But all that is a topic for another thread
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Old 12-22-2006   #36
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Default Re: the science of cables

Quote:
Originally Posted by Autiophile
You're right, this is a thread about the science of cables. There have been several of these threads over the past few days and it seems to me that the whole argument is an issue of perception vs. scientific measurement. By simply focusing on RLC or measurable audible differences we leave out the most complex part of the system, our minds.

Over on Headfi.com we have gotten into discussions about the differences in the shapes of peoples ear canals and how they impact sound, to the point where many individuals have seperate level controls for Left and Right channels to provide compensation. Before I digress too far, my point is simply to remind everyone of the complex, multivariate, nature of perception.
But you also have to keep in mind (no pun intended) that the brain makes an attempt to compensate for the early transduction mechanisms that may give rise to odd FR/phase behaviors. So ear issues, as long as they're not rapidly dynamic (eg. ear wax, eustachian tube dysfunction, sudden hearing loss, etc), are for the most part taken care of by the brain. That is, the shape of the ear canal and the pinna and the significant variation in the bones that underlie the transduction don't play much of a role in the end, because the brain has already addressed it.

So that no confusion arises, I should qualify that statement with this -- the brain can only process that information that's available to it. So when werewolf talks about the shape of the pinnae impacting vertical cues, it's something that the brain CAN'T compensate for because those cues are not physically present otherwise. It's not information that a simple gain control mechanism (something the brain is very good at) can account for.
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Old 12-22-2006   #37
 
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Default Re: the science of cables

Just a few more questions.

Wasn't there some rumblings this past year about the upper limit for supernova energy expulsion (the chandra sakkar or something)? Wasn't that fundamentally questioned and doesn't that affect the dark matter and dark energy theories?

and in a DS-21 like turn.... doesn't Dark matter/energy prove that there may be something goin on in wires and amps? we don't know what it is, but we know it's there
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Old 12-22-2006   #38
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Default Re: the science of cables

Wes = smartipants

I'll answer a question with another question : when we discovered that the orbit of the planet Mercury simply did not seem to follow that predicted by Newtonian Dynamics, were we all afraid that our bridges would start collapsing?

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Old 12-22-2006   #39
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Default Re: the science of cables

Quote:
Originally Posted by werewolf
Man these threads always go the same way ... the only mystery in the realm of cables may just be, why i never seem to learn
Difficult to resist, huh?

Quote:
2. The existence of dark matter and dark energy, which seem to cause to rate of expansion of the universe to be increasing ... beyond all expectation.
You know there's a problem when physicists have resorted to create names for ficticious "stuff" in an attempt to explain away nonlinearities that really shouldn't be all that unexpected in a nonlinear universe. That A+B don't equal C does not necessarily mean that there's a missing term on the left side of the equation. It could simply mean that the operator is wrong. Basically, I consider the whole thing to be a problem that only points out that we don't know everything there is to know about how the universe operates, rather than the notion that we're missing components. Which is why the whole notion of "dark matter" and "dark energy" are terribly misleading.

Quote:
Once again ... I am NOT suggesting that all cables sound the same. That's an hypothesis that would be ridiculously easy to disprove. I am, however, suggesting ... or rather, stating as factual with the same confidence that the earth will continue to rotate tomorrow ... that any sonic differences are attributable to RLC analysis (contact metallurgy and noise immunity aside).
I think you're giving in too much, werewolf. All but the most esoteric designs (which are probably also the most expensive) will provide virtually zero perceptible effects by virtue of the sound alone. And when you take into account the imperfections inherent in a car, any measurable effects will be completely swamped.
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Old 12-22-2006   #40
 
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Default Re: the science of cables

no, but I'd say our grasp on dark energy, dark matter, strings and such, is much less concrete than the formative grasp on newtonian physics.

But I digress.... back to Wire bashing.

On the subject of Speaker wires and weak links.... what's the purpose of silver wires when (for home speakers), the binding posts, the internal wires, coils in xovers, crossover circuit boards, and VC's are copper. And the solder is made from tin/lead....

what if *gasp* the vc is made out of aluminum.... (((shudder)))
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Old 12-22-2006   #41
 
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Default Re: the science of cables

So who is going to write up the tutorial on "How to Build Custom RCA's to maximize the RLC performance of your signal path"? Or, "How to time align your system by modifying the signal cable."

Does equipment that can measure RLC accurately enough for the purposes of tweaking RCA construction even in the realm of possibility for the average DIYer, cost wise that is?

If I knew how to properly measure RLC of the cable / source / amp system, what the heck I was looking at and how it affected the sound I'd Build some cables. It would be a neat experiment to build cable with different Wire and see if the preceived changes in sound match up with expectation from the scientific data.

I can see it now... Neutrik Connectors with Canare instrument cable from the head unit to the eq. Canare RG-6 connectors with Belden Coax from EQ to XVR, a Stinger RCA to the Tweeter amp (got lucky), Mogami twisted pair and Echimman (sp?) to the mid amp, Starquad with Parts Express special RCA to MB and Soundcraft RCAs with hand braided sliver Wire to the sub (for that magical bass extension, but all scientifically proven of course). Then you buy a new crossover and you have to start all over. AHHHGGGG...

Anyway, I really don't need another thing to have to tweak, but it would make me feel really smart to know how to measure and modifiy a cable to change the response of my system.

Thanks for bringing the technical knowhow Werewolf. You are making me want to go get out my old text book from the one EE class I took in college.

Tyler Herring
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Old 12-22-2006   #42
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Default Re: the science of cables

Quote:
Originally Posted by T-Ro
If I knew how to properly measure RLC of the cable / source / amp system, what the heck I was looking at and how it affected the sound I'd Build some cables. It would be a neat experiment to Build cable with different Wire and see if the preceived changes in sound match up with expectation from the scientific data.
That was done 25 years ago and published in the J.AES, at least for Speaker wires (whose potential sonic benefits should far outweigh RCA cables due to the much lower impedance load). Fred Davis was the author. If I recall, he even included in his test group a set of jumper cables he had lying around...
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Old 12-22-2006   #43
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Default Re: the science of cables

Mark's point is VERY well taken ... and helps to address the above post.

I have stated that the signal transmission can't be impacted unless RLC is impacted. Very true. However, this does not mean that any difference in RLC is audible. And it does not mean we should be on an eternal quest to minimize RLC.

A few cases-in-point :

1. Imagine an RCA cable connecting a preamp, with source impedance of say 200ohms, to an amplifier, with input impedance of say 10kohm. How much should I worry about reducing cable resistance from 2ohms to 1ohm?

2. In my above example (which I still need to finish), we saw a VERY long RCA cable introduce a low-pass at 80kHz. How much should I worry about improving that to 160kHz? Or 320kHz?
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Old 12-22-2006   #44
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Default Re: the science of cables

OK ... how does an 80kHz first-order lowpass impact phase in the audio band?

Here's the Transfer Function (derived by simple voltage division):

Vout/Vin = [1/jwC]/[R + 1/jwC] = 1/(1 + jwRC)

where w=radian frequency=2*pi*f, R=1k, C=50ft*40pF/ft=2000pF

In general, a Transfer Function is a complex function of frequency, which really just means that the frequency response has two parts : a magnitude function vs. frequency (often erroneously equated with frequency response in audio), and a phase function vs. frequency. All we need to do is find the magnitude and phase of a complex "number" ... or function of frequency, in this case

The Magnitude Response is :

|Vout/Vin| (in dB) = 10*log{1/[1 + (wRC)^2]}

somebody can tell me the magnitude response at f=10kHz, 20kHz, 40kHz, 80kHz, 160kHz, 320kHz

The Phase Response is :

Angle[Vout/Vin] = -arctan{wRC}

somebody can tell me the phase response at f=10kHz, 20kHz, 40kHz, 80kHz, 160kHz, 320kHz ... and in so doing, answer the question : what does the phase response of a first-order low-pass filter look like?

Last edited by werewolf; 12-22-2006 at 04:24 PM..
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Old 12-22-2006   #45
 
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Default Re: the science of cables

We could simply ask what affect phase has in the audio band as well - and bypass your little homework assignment.

Which is audible, but not disagreeable.
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Old 12-22-2006   #46
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Default Re: the science of cables

Absolute Phase : audibility is debatable ... but at some point it certainly is audible, as easily demonstrated by looking at extreme values of group delay.

Relative Phase : quite audible, as it impacts how one driver interacts with another acoustically (be it the corresponding driver on the other channel, or another driver on the same channel at crossover)

Once again, I'm not arguing in favor of cable sonics Just answering a question posted. No need to consider the homework if disinterested
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Old 12-22-2006   #47
 
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Default Re: the science of cables

-221? Imma double check my numbers.
-90
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Old 12-23-2006   #48
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Default Re: the science of cables

This is the Magnitude and Phase Response of the first-order low-pass filter formed by the cable capacitance & source resistance described above :


FREQUENCY.....MAGNITUDE........PHASE

10kHz.................-0.068dB........-7.2 degrees

20kHz.................-0.27dB..........-14 degrees

40kHz.................-0.98dB..........-27 degrees

80kHz.................-3.0dB............-45 degrees

160kHz................-7.0dB...........-64 degees

320kHz................-12dB............-76 degrees

640kHz................-18dB............-83 degrees

Conclusions :

- The magnitude response should look familiar : -3dB at 80kHz, asymptotically approaching a 6dB/octave rolloff as frequency increases.

- The phase response always seems to be a point of confusion ... there is no single number for the phase of a filter : -45 degrees at 80kHz, asymptotically approaching -90 degrees as frequency increases.

- Even in this artificially exaggerated case, the audio band impact ... including both magnitude and phase ... is minimal.

- Is this the response for any RCA cable? Of course not! Will it be different for a different source resistance? Yes. Will it be different for a different cable, of different length and capacitance? Yes. Can the techniques presented here be used to calculate the possible (but unlikely) audio band impact of any RCA cable? YES
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Old 12-23-2006   #49
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Default Re: the science of cables

Werewolf ...... You've blinded me with science !

I mean , doesn't your head like ...hurt ? LOL
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Old 12-23-2006   #50
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Default Re: the science of cables

Science (and logic, to Mark's point) will not blind you ... in fact, quite the opposite

It's the light of a best friend, for navigating your way through the dark world of audio bullshit
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