Speaker wire -> How far from electric wire?

Discussion in 'Archived Threads 2001-2004' started by Jim Tressler, Feb 1, 2002.

  1. Jim Tressler

    Jim Tressler Stunt Coordinator

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    I have searched the threads and get some mixed info on running speaker wire near electric lines. Some say dont, others say its ok, and others say make sure they cross at a 90 degree angle.. So.. which is it? Is there a recomended "safe" distance from speaker wire to electric wire? Should they cross at a 90 degree angle? One more question: What can cause interference in speaker wire?

    I am planning on tucking the speaker wire under the baseboard then sending it up the wall for the 6 feet or so for the surrounds.. sound good?

    thanks!

    jim
     
  2. Allan Jayne

    Allan Jayne Cinematographer

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    This is really a difficult quesiton, one that needs an electrical engineer to answer. But here are a few (quite technical) guidelines.
    All power carrying wires radiate some energy. Tore current the electric power wire is carrying, the more interference it is capable of causing. Also some electronic and electrical equipment, maybe in a neighbor's house or hospital or factory down the street, when plugged in and turned on, can put interference into the power line eonsisting of frequencies which when they radiate out that nearby power wire and are more likely to interfere with audio signals in nearby cables.
    The more current the speaker wire is carrying (for louder sounds or less sensitive (efficient) speakers, the less you will notice a given amount of interference.
    The amount of interference depends on the distance span as well as the proximity, for example (numbers are hypothetical and not necessarily correct) you may have more interference when the power and speaker cables are three inches apart stretching for ten feet compared with one inch apart stretching for two feet.
    Because speaker wires carry a fairly large amount of current that is not amplified further, and because the amount of interference is actually a very weak signal, you won't notice it most of the time. Whereas with low level signal cables such as from DVD player to receiver, once the interference gets in it is amplified along with the rest of the signal and that is why you notic it. Cables from microphones or from LP turntables (who still uses those?) carry even lower level signals and are thus more sensitive to interference.
    Now for the layman's advice. Here is something you can try. Turn on the system but turn the volume almost to zero. Have a family member or friend move the power cable around while you put your ear one foot from the speaker. If you hear a difference, move the power cable further away.
    Video hints:
    http://members.aol.com/ajaynejr/video.htm
    If you are dying Easter eggs light pink and you accidentally drop a wee bit of green dye in, the resulting color difference will be much more noticeable compared with dying the eggs deep red and the same wee bit of green was added.
     
  3. Mike LS

    Mike LS Supporting Actor

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    Short and sweet....what you're planning to do should work fine.

    Keeping the speaker wire under the baseboard will keep it about a foot or more away from the electrical wire, so you shouldn't have any problems there.

    It is true, that if the two wires have to cross each other, that they need to cross at 90 degrees....don't run the right next to each other to cross them.

    Since you're running baseboard wire.....it's extremely easy to check for interferance. Just run the wire temporarily next to that wall on the floor without tucking it, then run it up the outside of the wall to the speaker (go ahead and mount the speaker if it's not already) and hook them up....run them that way for a little bit and see if you have any problems.

    Plug something into the outlets that are close by and see what happens.

    You should be fine.
     
  4. David John

    David John Stunt Coordinator

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    If my memory serves me... it is more important to run video cables farther from A/C cables, and they should intersect at 90 degree angles.

    Otherwise you run the risk of getting 60 Hz hum bars visible on your video monitor. These look like slowly decending horizontal bars which are faintly visible on your video monitor.

    If you see these, you can try moving the A/C line or video cable until they go away.

    As far as speaker cable, the above posts have covered this, and I don't think you'll find much interference from them.

    You're more likely to get ground loop hums from you audio system.
     
  5. GarryW

    GarryW Stunt Coordinator

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    Go to Home Depot and pick up a voltage "sniffer". They are about $10 and you can use them to find stray voltage interference from power cords.
    You run it near a power cord, an it emits an audible beep. Record the distance from where it beeps, usually 1-2", mostly less, and keep your speaker wires away that distance.
    Check it out at www.gardnerbender.com/ and search for testing equipment. Look for the Circut Alert. Great little tweakers toy![​IMG]
     
  6. Bob McElfresh

    Bob McElfresh Producer

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    Jim: sometimes running speaker wires in the wall/ceiling/floor, you find AC power wires running as well. If this is the case and the wires have to cross, the suggestion is to try and make them cross at 90 degrees to reduce the interference.
    The longer 2 runs of wire are in parallel - the more likely they will cross-talk. The closer they are - the more likely they will cross-talk. The more power one is running, the more likely it will induce a signal in the other.
    So all 3 are variables.
    You would like to avoid all power wires if possible. The 90 degree suggestion is when you cant.
    PS: Make sure you run 3 sets of wires to the rear. Dont forget that rear-center speaker that is becoming popular with DolbyEX. The wire is cheap compared to your labor in installing it. [​IMG]
     
  7. Bill Lucas

    Bill Lucas Supporting Actor

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    While many of the answers given offer reasoning, none offer the correct reason. There is no need to bring an electrical engineer in for an answer. What is needed is the NEC code book. Here's what it says in a nutshell. You cannot run low voltage wiring with high voltage wiring. It is a serious code violation. If the wires run parallel they should be at least 12" apart. If they must cross they MUST cross at a 90 degree angle. The true answer has nothing to do with interference (which is a valid concern) and everything to do with building code requirements. Regards and good luck.
     
  8. Dan Hotch

    Dan Hotch Agent

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    Bill,

    While I know nothing about NEC Codes I do not think that your answer is completely accurate. The reason I say this is that there is a difference between low voltage wire and wire that happens to be suppling low voltage (i.e. speaker wires.) Low voltage wire is rated as such do to the thickness and the conductive properties of the sheilding that coats the copper wire strands. The average wires used for most plug in stuff (read: 115V 60Hz) is rated at 300V (not postive on this.) That means that a voltage potential would have to reach 300v before a spark would pass through the sheilding to something on the outside. "Low voltage wire" by contrast is just that, it normally has very thin sheilding. If you look at any speaker wire that you get the sheilding is at least as thick as 600V wire (although the conductivity may be lower.)The NEC Code you speak of could be for other reasons though.

    To the original post I am not an Electrical Engineer, just a Mechanical Engineer, but the stuff I am working on was CE tested for electromagnetic suceptibility and emissions a few months ago. The electromagnetic fields that are generated by the alternating current of your household wires (and all electromagnetic fields for that matter) fall off very rapidly with distance. I doubt that you would hear a difference if you had you speaker wires wrapped around your power cables.

    Look at it this way. In the telecommunications industry(where the frequencies are much higherand voltages are much lower) they have twisted pair cables that have metallic sheilding around the wires to sheild against EM distruptions. If it were any issue for speaker wires the Moster Cables of the world would be hyping things like this for hundreds of dollars.

    You should be fine.
     
  9. Earl Simpson

    Earl Simpson Supporting Actor

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    I don't have a firm answer to this, but do you know how hard it is to crawl through a dark attic in knee deep insulation. Try not to fall through the ceiling and then find the correct top plate to drill through at the exact location, fish the wires down the wall and try to pull them out the hole you cut, and then find out you drilled the plate hole in the wrong place for the hole you cut in the wall and then drill 4 more pilot holes and have the battery in you drill go dead twice. And now, you may ask yourself the question, " did I come near any non metallic cable?".[​IMG] [​IMG] [​IMG] [​IMG] [​IMG] [​IMG] [​IMG]
    Ok// sure! But I don't care! I know the NEC wants you to keep low volt wire and high volt wire out of the same conduit or raceway. This is for safety. If a high volt wire burns through the insulation or gets damaged through installation( strong possibility) it may short out against the low volt wire and electrocute someone who is working on the low volt wire thinking it only has low voltage on it.[​IMG] [​IMG] [​IMG]
    But this is not likely, but could and has happened. Just the odds! Just be careful when resetting Circuit breakers!!![​IMG] [​IMG]
     

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