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Cable Science breakdown

Discussion in 'Live Sound [BG]' started by fenderx55, Apr 14, 2009.

  1. fenderx55


    Jan 15, 2005
    Caught this on Gizmodo today, and even though it's mostly focused on cables for home audio, I suspect that the same principles apply. Thought it may be an informative little nugget to have floating around for the "Use the Search" set the next time there's bickering over $6 vs. $50 cables.

    Giz Explains: Why Analog Audio Cables Really Aren't All The Same

    While I've clearly stated that, despite Best Buy's 57 overpriced "choices," HDMI cables pretty much all do the same thing, this isn't the case with analog audio cables. Here's the physical explanation why:

    While there aren't a lot of parts to audio cables, there are more than you might think, especially on higher-end cables. Their goal, like most wiring, is to transmit an electrical signal from point A to point B without losing signal strength or clarity. But because this is the real world and not fantasy land, there will always be some kind of loss, and when the signal is analog—rather than digital—there's less of an all-or-nothing tradeoff. With the HDMI cables we tested, most could pass the required 1080p video and audio signal with no noticeable blips, but with analog, there are infinite gradations of signal that could actually make it through.

    What gets in the way of the signal? A cable has several key electrical properties that differ from manufacturer to manufacturer, and can be manipulated by the way a cable is constructed. Because that manipulation usually involves performance tradeoffs, cable makers themselves have to ask two questions:

    1. How much can I minimize the signal loss overall?
    2. If I have to compromise, what do I sacrifice and what to I preserve?

    I asked my friend David Kay, an editor at Audio Junkies, to help me sort out this mess, and we recently walked through all the electrical properties that have an impact on an audio signal as it passes along a cable. Here's the gist of our discussion:

    Resistance: How much opposition the cable's own length, shape and material impose on the signal passing through. Since the opposite of resistivity is conductivity, a better conductor material used to make a wire inherently means lower resistance. "Exceptionally pure and exceptionally drawn copper or silver is much more conductive than the cheap stuff," says Kay. "Some companies use rare earth materials, like palladium, which is supposedly more conductive than silver." The word impedance—often used in audio terminology—is essentially a derivative of electrical resistance.

    Measured in ohms, or rather milliohms, resistance is usually referred to by the letter R. The fewer milliohms of resistance, the better time you're gonna have.

    When wire makers are casting or drawing their metals into long strands, they take care to keep oxygen out of the process, and the more expensive cables take care to keep the metal hot while working with it, to avoid the build up of crystals. It is believed that oxygen and crystal buildup in the metals affect sound quality, because they add to the resistance. One of the most celebrated casting methods for super-pure, high-conductivity copper is called the Ohno Continuous Casting process, or OCC.

    Capacitance: "The ability of a body to hold an electrical charge," as Wikipedia puts it so concisely. A capacitor is basically two conductors separated by an insulator. If that sounds suspiciously like every speaker wire you've ever seen, then you're on to something. Modern capacitors found in consumer electronics are purpose built to hold charges, like smart, fast mini batteries, but even primitive cables can hold some kind of electrical impulse. If that happens, it's not going to get where it's going on time. And time, as it happens, is important when listening to music.

    Capacitance, indicated by a C, is measured in Farads. In the audio world, usually that's picoFarads (pF), the fewer the better.

    Inductance: Sparing you the nasty official descriptions, in this case, it's the potential for a conductor (wire) to generate an electromagnetic field based on the electricity flowing through it. Too much of an electromagnetic field can technically screw with the audio signal. (Britannica.com actually has some decent chatter on inductance, if you dare.)

    The Romulus to capacitance's Remus, these two are always at odds. Even if you can bring 'em both down, cable makers always reach a point where they have to make a tradeoff between capacitance and inductance. Says Kay, "The way you arrange wires in your cable, by twisting them, and by deciding how far to space the conductors apart—that all has an enormous effect. You want a balance—you don't want ultrahigh readings of one to get low readings of the other."

    Inductance is denoted with an L—apparently as a shoutout to some long-dead physicist. You track induction in Henry units (not making this up), also a shoutout to some dead dude, and yeah, they measure inductance in audio cables with microHenrys (µH or uH).

    The Dielectric, aka Insulation: One of the biggest disputes in high-end cable is how to insulate your conductors. Lay people tend to think that the plastic coating around a wire is there to keep the electricity from getting out, or other electricity from getting in, and while that's mostly true, the physics argument says that the signal itself travels between the conductor and the insulator, almost always referred to in cable science as the dielectric. The wave is technically jumping along the wire, bouncing off of each insulated wall as it goes. Because of this, some warrant that an insulator shouldn't be too absorptive. Cable makers tend to frown upon PVC, and smile at Teflon. In the middle, says Kay, are things like polyethylene foam. Teflon is expensive and harder to extrude over copper or silver wire, hence its price.

    There's more to insulation than a mere coating. In fact, some cable makers coat each individual strand of copper in what's called a Litz coating, in order to ensure the longevity of the cables, according to one of the makers. The strands themselves aren't microscopic—they're usually thick by typical standards—but inside each "wire" you find a bundle of smaller individually wrapped wires. You can imagine this is a bit of a pain to work with if you're stripping wire yourself, but some people do like it.


    Skin depth: As Stereophile's John Atkinson put it back in 1995: "There is an optimum conductor diameter for audio-signal transmission." This has to do with research conducted by a University of Oxford professor named Malcolm Omar Hawksford (bonus points for cool multicultural name), who said that lower frequency signals take longer to travel through thicker wire, creating an effect known as "time smearing." The solution was to bring the diameter down to somewhere between 0.5mm and 1mm per strand, in order to ensure that "a uniform current flow across the conductor is to be maintained over the audioband."

    In order for cable makers to avoid problems resulting from skin depth, some have resorted to making hollowed-out or irregularly shaped cables—like the hollow oval cable at left from Analysis Plus—or arranging skinny cables around a hollow center.

    Prof. Hawksford also corroborated a few other points that had been made (and that I mentioned above):
    • "The dielectric supports the majority of the signal during its transportation along the cable"
    • "Stranded conductors without individual [Litz] strand insulation appear to be a poor construction"

    Shielding: You may note that I haven't yet bring up shielding, even though it's a popular topic in audio cables. It's because you generally only shield interconnects, which are constantly carrying low-energy signals between heavy electrical components. Those weak signals are easy prey to external electromagnetic interference, while the higher-voltage stuff running through speaker cables tends to be impervious to that outside noise.

    Shielding comes in different formats, usually all at the same time, in order to cover different electromagnetic frequency ranges, from the low end, protected by a braided mesh of aluminum, copper or even silver-plated copper, to the high end, kept out by solid sheets of aluminum or mylar. An additional layer of carbon-filled (conductive) PVC is also used to block certain electromagnetic frequencies and to cut down on the tendency of some interconnects to be "microphonic," picking up vibrations that turn to sound. (At left, Cardas' interconnect with three layers of shielding, Litz-coated individual strands of cable, and even a hollow center—lots of principles at work here.)

    Kay says that, because of this vibration issue, there are even more unusual shields coming to market, including wires surrounded by beads and sometimes even fluids.

    The question is, how does this actually lead to differences in sound quality? Can people actually hear differences in cables when they are optimized in accordance with the physical properties I talked about up above?

    When proving his theory of skin depth, Professor Hawksford wrote, "I am not trying to say that this effect is necessarily significant, only that an error component is predicted by our theory and is shown by the measurements to exist." I think that sums up where the real division lies in the audio cable debate. Some people say they can hear it, others refuse to buy that these proven tweaks of electricity and electromagnetism are audible.

    You're not going to hear it on a $350 home-theater-in-a-box system that came with speakers thrown in. But if you spend a few grand per speaker, and a fair amount on a receiver, you just might stand a chance of hearing some differences. If you spend $100,000 on a home-theater setup, well, you've probably got the cash to buy any audio cables you want, so I'm not sure I give a damn what you buy.

    And as I mentioned up top, we're talking about analog cable here. It's true that anything passing electrical signals—be they analog or digital—will encounter these same issues, but as we've seen, the heavy demands of 1080p video mean you either see the picture or you see something revolting—there's less of an opportunity for nuance, which makes cheaper digital cables—especially ones with a guarantee—a more sensible purchase.

    This isn't necessarily a validation of extravagant spending when it comes to speaker cables and interconnects, but it does acknowledge that even skeptics can hear the difference between a $200 speaker cable and a $1000 speaker cable, given the right (generally very expensive) sound system. In fact, many say that higher-end systems reveal the qualitative difference between cheap and high-end cables better than they reveal any variation among various expensive ones. That is, the jump from $20 to $1000 is much more clearly audible than the jump from, say, $2500 to $5000.

    I get this, because when tasting wine, my ignorant ass can correctly identify the differences between a $9 white Burgundy and a $25 one, but I may have a lot of trouble sussing out what makes a $100 white Burgundy any better than that same $25 bottle. If you put a $100 bottle and a $1000 bottle in front of me and ask me to tell the difference, I'd probably just walk away. (Actually, I'd grab them and run, but only to sell 'em on eBay.)

    I'm not going to leave you with some direct answer. In fact, we've reached a nice pausing point where you can yell at each other (or me) about all the reasons you think all this stuff is real or total nonsense. The good news is, we're cooking up a version of the age-old analog cable test, to see what we can learn for ourselves, both with analytical gear and our very own ears. Meantime, please discuss this in comments, and if you have any suggestions for your own tests, I'd love to hear them below or via email.

    Also, there's a damn good chance you know more about electrical engineering than I do, and that you'd like to elaborate on or maybe even correct something I discussed above. Just don't be a dick about it—it's tricky to put this stuff into terms every interested party can understand, and in doing so, stuff gets left out. By all means share your knowledge, but know that this is just the beginning—not the final word.

    Further reading:
    • AVS Forum's hallowed "Expensive speaker wire vs. lamp cord?" thread
    • John Atkinson's useful though defensive argument for high-end cables (Stereophile, 1995)
    • Malcolm Omar Hawksford's mathematically dense proof of skin depth
    • WSJ article on audiophiles listening to expensive cables
    • The Cable Co., probably the biggest selection of different high-end audio cables
    • Audioholics Speaker Cable Face-Off
  2. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    I buy whatever cables are on sale or cheap. I have yet to have anyone convince me that the cable makes any difference at all, other than the length of the cable causing capicitance and loss of high end.

    Here's what happened to me once...I was at Best Buy, and the salesman tried to convince me to buy Monster cables for a stereo I was buying there. He took me to a display where they had two identical pairs of speakers, one with Monsters, one with the generic brand. He plays them both for me, and says, "Hear the difference?" Sure enough I did. The Monster setup was noticeably brighter.

    So I asked the guy if I could see the receivers they're plugged into. He seemed very reluctant to do it, but I insisted. So I look at the receivers, and the one with the generic cable has the treble rolled off! I set it back to where the other one was, and there was no difference at all.

    And yet this idiot still tried to convince me that Monster cables sounded better. I told him to pipe down with the Monster nonsense and give me the generic speaker cable. He says, "OK, but I think you're making a mistake."

    I said, "Dude, I've been playing music professionally for 25 years. Cable is cable. You obviously get a higher commission or some kind of bonus for selling Monster cable, but I'm not buying it, and if you pursue it any further, I'm not going to buy anything."

    So he backed off...until we got to the extended warranty and I had to tell 3 people, including the manager of the whole store, that I will never buy an extended warranty so either give it up or lose the sale. But that's another thread for another time.

    So I will leave the audiophile cable nonsense to the audiophools, and I will buy inexpensive but well-made cables and be much happier that I didn't get ripped off.
  3. fenderx55


    Jan 15, 2005
    Best buy is pretty sketch. Just thought I'd throw this out there.
  4. greenboy


    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    A few good things in there, but as soon as you bring up something from a Stereo audiophile magazine and place it in the same paragraph as "science" you've pretty much lost me. Unless I see actual tests conducted replete with referenced graphs and a list of tools and procedures used, it's just hearsay and usually with a dollop of junk science thrown in for good measure.

    One of the favorite tricks that at the surface might appear to have validity is often trotted out when discussing skin effects. Sure, they might exist, but they operate so far above the domain above audio frequencies that to discuss them in audio use is not germane. To talk of speed when you are at around .7 the speed of light and traveling down maybe a few meters of cable is ridiculous.

    Pardon me now, I need to go polish my audiophile fuses - the AC disdains passing through them in their present state.
  5. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Make sure you wear your special anti-static latex gloves when handling them!
  6. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Obviously, but the point still remains.
  7. TL5


    Jun 27, 2005
    In some cables I can hear a difference. The trick is; WHich is better?
    That is very subjective I think.

    Here's a practical example:
    When I originally wired my pedal board I used Belkin cable with switchcraft connectors.
    I set everything up and EQ'd my amp and was happy.

    Later, I allowed someone to convince me that George L cables worked better on a pedal board, so I re-worked it. Sure enough, it sounded different. So I EQ'd my amp to sound just like it did before, and I'm still happy.

    The point being, even though I heard a difference, I was capable of achieving my tone with either. So in my case - maintenance and longevity will be the determining factor on which is better.
  8. greenboy


    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Or thought you did. I'm not seeing any side-by-side during-the-same-time-period A/B testing there. The ear is subjective enough without introducing the memory as another variable.
  9. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    I read the OP. What I noticed was that as the concepts got more difficult, the explanations got more incoherent. This is the mark of someone who doesn't understand the subject matter, and is basically bluffing. He gets Resistance more or less OK, makes a buffoon of himself on Inductance, and is in outer space by the time he gets to Dielectrics.

    He also plays the typical audiophile trick of talking in qualitative terms, while rigorously avoiding any attempt to quantify the magnitude of effects, even though the resistance, inductance, and capacitance, of cables are known quantities. Knowing the magnitude is crucial because it determines audibility.
  10. hbarcat

    hbarcat Supporting Member

    Aug 24, 2006
    Rochelle, Illinois

    Excellent post, fdeck.
  11. hbarcat

    hbarcat Supporting Member

    Aug 24, 2006
    Rochelle, Illinois
    Since the opposite of wet is dry, a better drying material used to make a towel inherently means less wetness.

    Unless it's one of those times when you want higher capacitance, then the more the better. Or one of those times that it doesn't matter. In which case it doesn't matter.

    Whoa, slow down with the technical jargon there, Poindexter. I haven't gotten to the chapter in the electrical engineering textbook where they describe "audio signal screwing".

    Is that how an electromagnetic wave propagates??? :confused: My college textbooks sure got it wrong. :meh:

    Geez, I didn't realize I needed to be Richard ******* Feynmann to know which audio cables to buy. :rollno:

  12. Yes. Most of the "science" in that is indeed broken down.

    In the sense that a car with a blown head gasket is broken down.

  13. fokof

    fokof One day ,I'll be in the future

    Mar 16, 2007
  14. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    I've come to a conclusion...I hate audiophiles. They're as dumb as witch burners in Salem in the 1700's, and they're as arrogant as Rush Limbaugh, Bill O'Reilly, and Bill Maher combined.

    These audiophool threads remind me of the time on Penn and Teller's BS that a water bottling company wanted people to try out different "flavors" of water. The waiter would suggest to the people certain aspects about the "flavor," and these pretentious yuppie a-holes would discuss how different each water is. Meanwhile Teller was out back with a water hose filling each bottle with tap water.
  15. jmattbassplaya

    jmattbassplaya Looking for a gig around East Islip, NY!

    Jan 13, 2008
    Long Island, NY.
  16. seanm

    seanm I'd kill for a Nobel Peace Prize! Supporting Member

    Feb 19, 2004
    Ottawa, Canada
    There is a huge difference in quality between an $8 cable and a $20 cable. After that it is all snake oil.

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