Can I use speaker wire for a powered subwoofer?

Discussion in 'Archived Threads 2001-2004' started by Francis_Y, Dec 11, 2002.

  1. Francis_Y

    Francis_Y Auditioning

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    I searched through previous posts, but didn't get a complete answer to this question.

    I know that usually you need coax for line-level output to a subwoofer, but my new house came prewired with speaker wire going to the back of my family room, two pairs for each side (left and right surrounds). Since I don't biwire my speakers, I was wondering if I could use the extra pair of wire so that I don't have to put extra cables down to my powered Energy Take 5 subwoofer.

    In other words, is there a way to solder on RCA plugs onto a pair of plain speaker wire to carry line-level output, or does that not work at all? I cannot use speaker-level outputs to the subwoofer, because there aren't enough wires to carry the signal back to the front speakers and simultaneously wire the surrounds.

    Equipment involved: Denon AVR-1700, Energy Take 5 speakers and powered subwoofer, prewired family room, and one Monster Cable subwoofer cable now useless because its not long enough.
     
  2. Bill Kane

    Bill Kane Screenwriter

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    ...wont address your main question, but will observe:

    You were going to use a Monster subcable, presumably along the room baseboard, but came up short? Now, you are thinking of using extra rear surround spkr wire -- meaning your sub is toward the rear of the room?

    1. Consider placing the sub in the front corner, the usual default position, decor/WAF willing, if the existing sub cable run fits, and you can get the wall outlet and surge protection you want.

    2. Since this is low-voltage line-level can you add more sub cable with and RCA barrel adapter?
     
  3. John Garcia

    John Garcia Executive Producer

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    I'm going to guess the two pairs in the rear are for 7.1, not bi-wiring.

    I would not solder an RCA to the speaker wire, but you might be able to get away with a speaker level to line level adapter on both ends. I don't think this would be the best idea, but it should work. Should be able to get this at Radio Shack.

    The other, and possibly more obvious solution, is what Bill said - put the sub in the front of the room near your gear, preferably in a corner.

    If you are OK with just running a long cable, this can be achieved with regular, inexpensive, coax (cable TV type) cable and RCA connectors designed for attachment to this type of cable (which should also both be available at Radio Shack).
     
  4. Bob McElfresh

    Bob McElfresh Producer

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    Hi Francis, Welcome to HTF! [​IMG]
    I'm afraid your plan is likely to fail.
    Your LFE output is called "line-level" or "un-amplified" signals. It's basically a 0-2 volt signal with no current. It needs a coaxial cable to shield the weak signals from noise & outside interference. Your speaker wire is almost too-thick for the signals to travel, and the lack of shielding means you are likely to pick up 60 hz noise from nearly any nearby power wire. This will swamp the LFE signal and simply make the sub give a loud, constant hummm.
    Most people prefer the 'sub-up-front' placement anyway. You get a lot of wall-reflections from the sub which help hide the location, but you CAN sometimes tell where the upper sub sounds are coming from.
    Hope this helps.
     
  5. Francis_Y

    Francis_Y Auditioning

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    Thanks all for responding!
    To Bill: My Monster subwoofer cable came from my old apartment, and now it is not long enough to reach the receiver in my new home, even when the sub is placed at the front wall. A female/female RCA adapter would work, but my wife's whole objection is to having the cable run in front of our beautiful new fireplace mantle. [​IMG]
    To John: Perhaps the pairs are for 6.1/7.1, but all four wires are bound up in one big blue sleeve, which doesn't pull that far out of the wall. You wouldn't be able to achieve much separation between back surrounds/centers with the way the sleeve is, so I'm not sure what its for. I think coax would be too stiff for the setup I'm looking at, there are like seven 90 degree turns on the way to the receiver. :p)
    To Bob: Thanks for the explanation... now that I understand why its theoretically a bad idea, I wonder if anyone's tried it anyway. Also, I did recently buy a long (24 ft) cable from Radio Shack that had RCA termination and what looked like thin white speaker wire inbetween. I wonder if this type of wire is just for cheesy speakers that are not powered but still use RCA plugs (i.e. boom box speakers).
     
  6. David Harris

    David Harris Stunt Coordinator

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    The question is can i use speaker wire to carry sub signal.
    A better question might be should i use speaker cable to carry signal to my sub...and the answer would be no, because subwoofer cable has a 75 ohm impedance and is properly sheilded. Using the wrong impedance wire may cause premature equipment faiure, and is most certainly going to sound like s@#%......good luck 73
     
  7. Brian Fellmeth

    Brian Fellmeth Supporting Actor

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  8. Bob McElfresh

    Bob McElfresh Producer

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  9. Francis_Y

    Francis_Y Auditioning

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    Hi all,
    Well, I tried it anyway... hooked up the subwoofer to the radio shack RCA-terminated speaker wire and then did A/B tests against the Monster Cable subwoofer cable.
    Found: 1) if the speaker wire is just connected to the subwoofer and not to the receiver, you hear a low hummm coming from the subwoofer.
    2) if the speaker wire is then plugged into the receiver, the subwoofer responds with a very loud pop before becoming almost entirely silent (i thought i could perhaps hear the tiniest of hums, and only if i turned the subwoofer to volume level 8 or above).
    3) if i did the same with the subwoofer cable, there was no hum but a small pop if i plugged the cable into receiver while the subwoofer was live. obviously no hum while every was plugged in but no signal was being carried.
    4) in a A/B test of the two cables during scenes from The Matrix DVD, i could not discern any difference in the output of the subwoofer.
    Conclusion: Even though the hum was so low as to be meaningless compared to the hum coming from my living room lights (due to a dimmer transformer) and the hum coming from my refrigerator in the kitchen, it psychologically disturbed me enough to know it was there that i'm going to avoid using speaker wire.
    Agh. Another $60 gone towards new cable. [​IMG]
     
  10. Shawn.G

    Shawn.G Second Unit

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    Sorry I can't help, but is your monster sub cable for sale? It could help you towards that $60.
     
  11. Brian Bunge

    Brian Bunge Producer

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    Francis,

    There's no need to spend $60 for a new cable. Simply get some coax from Radio Shack and add RCA connectors on the ends. It'll work just fine and be much cheaper in the long run.
     

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