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Discussion in 'AV Receivers & Amplifiers' started by dts_boy, Dec 3, 2001.

  1. dts_boy

    dts_boy
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    look at rhx certified cable...it specifys the max length, why would that be then? i think iwlson is wrong, sorry mate, but maths and real life are very different!
     
  2. DodgeTheViper

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    dts_boy ,

    Once again we are in agreement. I also think that iwilson is wrong.
    Why do so many manufacturers recomend max lengths for their cables, wether it be video or audio cables. Could it be due to a loss or degradation of signal en route ? Reviewers in magazines also recomend it.

    Iwilson, i think you are in a minority.
     
  3. iwilson

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    1. dts-boy, mozzer if I´m wrong I´d like to hear your reasoning, other than I just know its different.
    2. I never said there wasn´t a limit on cable length. Belden has a useful table on calculating the max length of speaker cable
      here.
      [/list=1]

      The chart in the above link basically says that the smaller the diameter the greater the power loss and the shorter the length.

      If you had read the other thread carefully you would have seen the discussion was about the length of the cable affecting the timing and also about the resistance of speaker cable causing damage to an amplifier. Your question was separate and I hope I´ve answered it to your satisfaction now.

      For those wondering this belongs in this thread

      Ian
     
  4. Guest

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    Thanks

    We may still be discusing cable lenths but the Thickness/loss table will be of great use
     
  5. chips

    chips
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    iwilson,
    my post in the other thread was to point out the error of your statement:-
    "There is no difference in the resistance of a copper cable 1m long vs. a cable 10m long or even 100m long. If resistance in copper increased at the rate you're describing electricity would have a very hard time going from your switch box to your equipment - never mind getting from the power station to your home."
    I would be interested to know if there are any valid reasons for matching cable lengths.
     
  6. iwilson

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    I understand and apologise if my reply was a little sharp. There is of course a difference but it's so slight that it's irrelevant in the context of the discussion.

    Ian
     
  7. Lowrider

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    Any difference, even the smallest, is still a difference...

    Confucio ;)
     
  8. Guest

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    This cannot be true!

    I grant you that speaker cable resistances MAY be so small as to be Insignificant but if the resistance is X/Meter then 10X and 100X is much larger that X. But if the resistances are as low as you say then it would be unlikely to affect the sound.

    So we're back to why are we told that speaker cables should be the same length per pair?
     
  9. iwilson

    iwilson
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    Here´s a link to an interesting read from a proaudio company.
    Nothing about unequal lengths, but in one of the graphs you can see that the power loss for a fifty foot run of 10AWG @ 8 ohm´s is .01% so if the other cable was 25 feet it would have a loss of .005%. So clearly a difference of .005% is not going to be detectable to the human ear. There is a good explanation of other effects as well.

    Ian
     
  10. Guest

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    Again Thanks

    This is the sort of stuff we sould be reading in HCC. Yes I like the reveiws but the odd artical on speaker cables and how they work would be good.
     
  11. T1000

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    I agree, it would be great if HCC did something about 'Home Cinema myths'. I know Ian is right with what he has said but I still cut my cables to equal length!!

    Jonno
     
  12. philmate

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    Sorry chaps,
    But I think the the whole thing is pants, in a smallish inviroment I've tried various cables including two by two and I ( sad oldish git) who may be banished from this country) have'nt been bowled over by/noticed any difference between stuff cheapley available/cost effective cables or cables costing considerable more . Remember the cables do not make something sound better but maybe different, yawn... ..I've listened to stuff from Rayleigh HI-fi, No disrespect and really cheap stuff and if you really listen, it may be just me.... but I doubt it's what you really get for your your money if anything(there's probably cheaper upgrades) I beleive they are taking your money and boy are they laughing. Anyway I have to go to attend the abandoned starling chicks now.
    Philmate.
     
  13. Reiner

    Reiner
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    Logically the longer the cable the higher the resistance and hence higher loss.
    Installed once for a friend a 4mm² cable and the difference was immediately noticable, more bass than compared to what he used before (which I think was 1.5mm²).
    However, this does not mean it did sound better but the above is basic phyiscs and not subjective in any way.

    As for comment from chips about the power station: the loss (due to the high resistance) is indeed very high, that's why you have high voltage lines which carry a couple of hundred thousands volts and not the 230V which comes out from your wall plug. A transformer station near your housing area will make sure that the remaining voltage (which still is ten- or hundreds of thousand volts) is converted to the required level.

    However, the difference in our environment (homecinema), where we are talking about a couple of meters might indeed be neglectable, though if someone thinks it does make a difference please do as you think it's right or feel safe about it - in fact I also cut my front speaker cables to equal length without that I could actually argue why ....
     
  14. iwilson

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    Hi Reiner, I don't want to be anal about the subject. But I think it's interesting and important sometimes to understand the physics behind the sound and pictures coming from our gear - if only to be able to cut though a lot of the pseudo science thrown at us.

    Just to clarify your explanation of why powerlines carry such high voltages. Powerlines carry high voltages not because the losses due to the resistance of the wire are so high, rather because it's more efficient to do so.

    When electricity flows across long wires some of the power is lost in transporting it. The amount of power efficiency is R/I2 (R is resistance, I is current). So clearly for most energy efficiency it is best to keep the current as low as possible. Power is equal to the voltage multiplied by the current. So if the voltage is very high, the current can be very low, and the system remains efficient.

    I'd like to see an Audio magazine run a series of articles on inductance, capacitance, resistance etc, explaining in the kind of language everyone can understand how these terms affect cables and equipment.

    If everyone here is cutting speaker cables to the same length what are you doing with the excess? If you're coiling it up into a neat roll you're introducing inductance....

    Ian
     
  15. chips

    chips
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    Reiner,

    Not my comment about the power station, if you re-read my post you will see.
     
  16. Reiner

    Reiner
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    Was a quote, wasn't it? Sorry ...
     
  17. Guest

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    This is a very interesting subject and all that.......but all in all the losses being talked about are only of interest to those who really listen closely......ok, if you have dramatic variations from the accepted method......its likely something will sound wrong. But for the most of us we should just connect it as is advised and enjoy the stuff! There are a million and one places that the signals are degraded more than speaker cables will ever do........in fact we quaintly call it an integrated amp.

    i'd love to argue the intricicies of electrodynamics, but thats just boring!

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