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Speaker Cable Length?

Discussion in 'Archived Threads 2001-2004' started by Mark Butler, Oct 4, 2001.

  1. Mark Butler

    Mark Butler Stunt Coordinator

    Aug 7, 2001
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    I am replacing my cables to my speakers and I am wondering to what length I should have my cables cut to. I have heard that your cables should all be the length of your longest run ie. 25 foot run to the rear surrounds, all cables should be 25 feet, to maintain proper sound imageing.
    Any help would be appreciated.
  2. Selden Ball

    Selden Ball Second Unit

    Mar 1, 2001
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    If you have heavy guage wires (e.g. 12 or 10 guage) then my experience has been that the length really doesn't matter.
    If you have thinner wiring (e.g. 18 or 16 guage) then you probably do have to worry about the resistance of the longer runs, especially if you have low impedance speakers. In this case, matching the lengths probably does make sense.
    "boutique" cables seem to tend to be more affected by substantial differences in lengths. Too often they're actually designed to make subtle changes to the sound.
    Longer cable runs do increase inter-wire capacitance
    as well as inductance, which can lead to almost imperceptable sonic changes, slightly filtering out the highest frequencies. However, the electical changes to the signal due to differences in cable lengths are usually miniscule compared to the speaker-to-speaker variations in the internal crossover networks among speakers of the same model.
    Also, it's probably not so good an idea to simply coil up the excess cable. That makes an ideal pickup for noise induced by fluctuating magnetic fields (like from motors in refrigerators or other pumps). Rather coil it in a large figure eight that you fold over in the middle. Induced currents will tend to cancel in alternate levels of the coil.
    These signals would be very tiny, anyhow. Unless you have an extremely low noise floor in your listening room along with gigantic motors nearby, you probably wouldn't hear anything.
    To put it another way, these are 'tweaks'. If you can hear the difference or if it makes you feel better, by all means match lengths, but avoid coils.
  3. Bob McElfresh

    Bob McElfresh Producer

    May 22, 1999
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    Mark: the "all speaker wires must be the same length" is a audio myth. Probably kept alive by salesmen who get commission and sell expensive speaker wire by the foot.
    (We did the math once and figured out that it took a difference of 80 feet to get a 1% phase shift in the sound. This means one speaker with 81 feet of wire, and the other with 1.)
    As for resistance, the WORST numbers I have found for 12 ga wire is 0.018 ohms / foot. This means you need about 55 feet to give you a 1 ohm resistance. But you dont care! You are going to use a sound-meter to adjust the levels and this compensates for any resistance in the wire.
    Several speaker sites recommend the following rule of gauge for a length of run:
    0-10 feet : 16 ga
    10-20 feet : 14 ga
    20-?? feet : 12 ga
    But most of us simply use good 12 ga all over the place.
    Cut the wires to leave a foot or two of slack so you can move the speakers around a bit. I also like to have an annual "cleaning" where I disconnect everything, dust, re-connect. And I trim off about 1" of speaker wire at each end to get rid of any oxidized copper that built up.
    I also like to make the speaker wires coming out of the back of my receiver flow away from the interconnects and power wires.
    Hope this helps.

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