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Thread: Speaker cables and DC resistance

  1. #1
    Join Date: May 2008

    Location: U.S.A. Neo-Socialist Kalifornski

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    Default Speaker cables and DC resistance

    I have 2 meter speaker cables 7 Awg and they measure 5 mili ohms and 5/6 mili ohms (meter bounced between 5 and 6), that is 5 or 6 hundred thousands of an ohm right?

    DC resistance for each speaker is 7.5 ohms. each. So short runs of heavy speaker cable don't even matter, for the most part they are electronically invisible?
    There is more likely more deviation of ohms in the crossovers and speaker coils than account for my speaker cables combined .
    Why all the hype about heavy speaker cables?
    Jeff :UBERTHREADKILLER

  2. #2
    Join Date: Oct 2012

    Location: The Black Country

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    I'm Alan.

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    It is 5 or 6 thousandth of an ohm, or 0.005 ohms.
    As you say completely negligible.

  3. #3
    Join Date: Nov 2010

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    I'm AnDreW.

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    Cables are a weird subject, indeed! I used to run 4mm2 VdH studio blue cable, great sound, cheap and lasts a lifetime. I tried the 6mm2 version and things improved even more. How? I suppose it's just a case of trusting my ears.
    SS

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  4. #4
    Join Date: Jan 2009

    Location: Essex

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    I'm openingabottleofwine.

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    The ohmic loss in the speaker cables is negligible (< 0.1dB). Of more importance perhaps is their effect on the damping factor. The resistance of the speaker cable will appear in series with the output impedance of the amplifier so potentially reducing the damping factor.

    Let us assume the amplifier is a solid state design with an output impedance of 0.02 Ohm. With a speaker of impedance 7.5 Ohm, the damping factor is 375. With the speaker cables the output impedance as seen by the speaker is 0.025 Ohm, so reducing the damping factor to 300. This makes very little difference to an already very high damping factor.

    With a valve amplifier the output impedance can be an Ohm or more, implying a damping factor of 7.5, and with the speaker cable this is reduced to 7.46. Totally negligible.

    That is the advantage of using short speaker cables. I use monoblock power amplifiers located directly behind each speaker, so the speaker cables are less than 1 metre long (actually 30cm).
    Barry

  5. #5
    Join Date: May 2008

    Location: U.S.A. Neo-Socialist Kalifornski

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    Quote Originally Posted by Barry View Post
    The ohmic loss in the speaker cables is negligible (< 0.1dB). Of more importance perhaps is their effect on the damping factor. The resistance of the speaker cable will appear in series with the output impedance of the amplifier so potentially reducing the damping factor.

    Let us assume the amplifier is a solid state design with an output impedance of 0.02 Ohm. With a speaker of impedance 7.5 Ohm, the damping factor is 375. With the speaker cables the output impedance as seen by the speaker is 0.025 Ohm, so reducing the damping factor to 300. This makes very little difference to an already very high damping factor.

    With a valve amplifier the output impedance can be an Ohm or more, implying a damping factor of 7.5, and with the speaker cable this is reduced to 7.46. Totally negligible.

    That is the advantage of using short speaker cables. I use monoblock power amplifiers located directly behind each speaker, so the speaker cables are less than 1 metre long (actually 30cm).
    Barry,
    This is my amp, and it's specs . https://www.manley.com/legacy/mst/

    The Damping factor is 5. I think im still ok?
    Jeff :UBERTHREADKILLER

  6. #6
    Join Date: Jan 2009

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    I'm openingabottleofwine.

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    Quote Originally Posted by goraman View Post
    Barry,
    This is my amp, and it's specs . https://www.manley.com/legacy/mst/

    The Damping factor is 5. I think im still ok?
    The quoted output impedance is 2 Ohm, so implying a nominal speaker impedance of 10 Ohm. With your cables the output impedance is increased to 2.005 Ohm reducing the damping factor to 4.99. This is an utterly negligible change.

    Whether this is sufficiently high is open to debate, and one with which I'm not really qualified to comment (I use electrostatic speakers myself,which have a very low moving mass, so little damping is required).
    Barry

  7. #7
    Join Date: May 2008

    Location: U.S.A. Neo-Socialist Kalifornski

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    Been there, I had Sound Lab electrostatics and still miss them. Very little moving mass is an understatement . I still find it funny that I had to adjust the Bias from time to time.
    Jeff :UBERTHREADKILLER

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