Bi-Wiring Cable Differences

Discussion in 'Archived Threads 2001-2004' started by ron_kolarovic, Feb 12, 2002.

  1. ron_kolarovic

    ron_kolarovic Auditioning

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    My front L/R are boston acoustics which are bi-wire capable but presently they are not wired as such - I have 12 gauge cable to each.

    The question is: should the same type of cable be used ( 12 gauge ) if I was to convert to bi-wiring, or could the high frequency wire be a lighter gauge ?
     
  2. Bob McElfresh

    Bob McElfresh Producer

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    Hi Ron. Welcome to HTF.[​IMG]
    Short Answer: it probably does not matter, but following the theory, the high-frequency wire should be thicker, and the low-frequency wire thinner.
    Long Answer: A long run of speaker wire will "slant" the sound. It will reduce the higher frequency sounds, but leave the lower-frequency sounds alone.
    This is why some speaker sites recommend:
    1-10 ft: 16 ga
    10-20 ft: 14 ga
    20+ ft: 12 ga
    The thicker wire reduces, but does not eliminate this effect.
    With your short runs, it likely does not matter. But the higher-frequency sounds are affected by the wire thickness so it should have the 12 ga.
     
  3. ron_kolarovic

    ron_kolarovic Auditioning

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    Ok, the next question is - why ?

    Assuming the high & low frequency loads are in the same range of impedance ( 8 ohms nominal ) why would the thicker ( 12 guage ) be better for the higher frequencies ? If anything, I would have though the reverse. The thicker, lower resistance cable to the low frequency ( woofer ) load to reduce the distortion from damping factor considerations, which would be less pronounced than with the high frequency load.
     
  4. brucek

    brucek Second Unit

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    ron,

    The frequency dependant resistance (reactance), is as a result of the capacitance and inductance of speaker wire.

    The capacitance creates such a small effect it can essentially be ignored, but the inductive reactance can be significant in longer speaker runs and is indeed a factor in "rolling" off of upper frequencies. This is as a result of the series reactance increasing as the frequency increases. Interestingly, inductance changes very little with gauge, so changing to a thicker or thinner wire would have little effect in this respect. Generally, inductance is altered by geometry. You'll see a few companies getting creative with interweaving their wires and altering the inductance as a result.

    Considering the cable by itself, the simple DC resistance (DCR) of a cable has an equal effect on all frequencies and results in a "power loss", in the form of heat. This loss increases with length and also wire thickness, with greater loss in a thinner wire. But this is considering the cable with a purely resistive load, which a speaker isn't. The impedance curve of a speaker is far from linear. If we use a sufficiently small speaker wire such that it becomes an appreciable portion of the speakers impedance you can create a significant non-linear response. Don't go this route. Generally though, the gauge of speaker cable will affect system damping and power loss in the wire.

    Either way, I would recommend that the 12 gauge wire you are using is sufficient. If you're looking for a positive thing to do, you could change to 10 gauge or make your speaker wires shorter. This will increase your system damping factor. There's really no scientific support for bi-wiring, only anecdotal evidence. Don't waste your money.

    brucek
     

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