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In my house, I only have an underground conduit for electrical cable. I have a home theater system, but there is no separate underground conduit for home theater wiring. I want surround sound with front and rear speakers, so I need to pull underground cable for rear speakers.

My questions:

  • Should I pull my home theater wire for rear speakers through that electrical cable conduit?
  • If I do this, will I get sound distortion?
  • If yes, is there any specific cable which I can use that would allow the electrical cable and sound cable to be in the same conduit and not get any sound distortion?
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Have you considered going wireless for the rear speakers? I have a system with a dongle that jacks into the base unit and a receiver that's wired to the rear left and right speakers. This avoids the wire running from the base unit to the speakers at back of the room, so you just have two separate runs, one across the front of the room and one across the back. Fancier systems would omit all the wires. –  Jeremy W. Sherman Sep 14 '12 at 16:03
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3 Answers

You really want to keep these separate in a high quality audio setup, as you will get interference...especially through a sub.

I would even recommend routing the cables in entirely different directions if at all possible to minimise mains hum. Is there no other route for them? As an example, my mains wiring is in the walls, so where possible I have my audio wiring in the floor or above the ceilings.

If you absolutely can't avoid running them together, get yourself a cable that has a decent screen and make sure it is earthed.

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Keeping power and speaker ~6" apart is generally fine. If they have to cross, make them cross at right angles. If they do run along side each other for short distances you probably won't notice anything, but I would definitely not want to do it for the length of a room unless it was shielded cable. If you have a powered sub (eg you run line-level signal to it) then usually that is done with coaxial, and I am not sure if that would be affected in the same way by mains or not -- anyone know? –  gregmac Sep 14 '12 at 15:08
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According to NEC 300.3(C)(1), you can only run the speaker cable in the same enclosure as a higher-voltage circuit as the insulation of speaker cable is rated for the voltage of the higher-voltage circuit.

NEC 2008 300.3(C) Conductors of Different Systems

(1) 600 Volts, Nominal, or Less. Conductors of ac and dc circuits, rated 600 volts, nominal, or less, shall be permitted to occupy the same equipment wiring enclosure, cable, or raceway. All conductors shall have an insulation rating equal to at least the maximum circuit voltage applied to any conductor within the enclosure, cable, or raceway.

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If you can avoid it, you should not run high voltage and low voltage lines in parallel. They should be separated and should intersect at right angles when they need to cross paths.

You will likely get some interference, but perhaps you won't notice it. No harm in trying.

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Inductive coupling may be a concern, in some situations. –  Tester101 Aug 29 '12 at 15:50
    
@Tester101 two lines running parallel (as in a conduit) should not have any meaningful inductive coupling. If one conductor had a loop, or were twisted around the other, then perhaps... but I sincerely doubt in this case. –  Matthew Aug 29 '12 at 17:06
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