Shielding speaker runs from electrical lines

[mod]

I've read about running speaker cables to cross electrical lines at 90 degrees and to not run parallel to electrical in close proximity. In situations where you just can't avoid the closeness to electrical lines, what's a good way to insulate between the speaker cable and electrical cable to prevent interference? Does some thickness of wood or rubber or sheet metal work?

 

[Midcow2]

shileding = outer metal jacket

I've read about running speaker cables to cross electrical lines at 90 degrees and to not run parallel to electrical in close proximity. In situations where you just can't avoid the closeness to electrical lines, what's a good way to insulate between the speaker cable and electrical cable to prevent interference? Does some thickness of wood or rubber or sheet metal work?

If you can get a shielded cable it is best. Shielding is actualy an outer metallic sheath.

Here is an example:
http://www.bluejeanscable.co.uk/store/6channel/index.htm
blue jeans LC-1 or Belden 1505F

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A shielded cable is an electrical cable of one or more insulated conductors enclosed by a common conductive layer. The shield may be composed of braided strands of copper (or other metal), a non-braided spiral winding of copper tape, or a layer of conducting polymer. Usually, this shield is covered with a jacket. The shield acts as a Faraday cage to reduce electrical noise from affecting the signals, and to reduce electromagnetic radiation that may interfere with other devices. The shield minimizes capacitively coupled noise from other electrical sources

 

[Marshall_Guthrie]

If you're talking speaker wires as in the wires connecting your amp(s) to your speakers, those are much less likely to pick up audible noise from RFI (because they are speaker level, not line level signals). I wouldn't stress it.

 

[TLS Guy]

If you can get a shielded cable it is best. Shielding is actualy an outer metallic sheath.

Here is an example:
http://www.bluejeanscable.co.uk/store/6channel/index.htm
blue jeans LC-1 or Belden 1505F

====

A shielded cable is an electrical cable of one or more insulated conductors enclosed by a common conductive layer. The shield may be composed of braided strands of copper (or other metal), a non-braided spiral winding of copper tape, or a layer of conducting polymer. Usually, this shield is covered with a jacket. The shield acts as a Faraday cage to reduce electrical noise from affecting the signals, and to reduce electromagnetic radiation that may interfere with other devices. The shield minimizes capacitively coupled noise from other electrical sources

I would not advise using shielded cable for speaker wire. The capacitance is significant, as a loudspeaker is a low impedance load compared to a sub LFE input. For one thing the capacitance of a long run shielded cable will be significant given the low impedance termination and that can lead to high frequency loss. The capacitance is high enough that this has been known to make some amps go into unstable oscillation.

The capacitance of about 4 ft of shielded cable is about 50pf to 75pf, so with a long run you can see it becomes highly significant. Even for long high impedance runs this is a problem, which is one of the reasons why for long runs balanced terminations are advised.

I think it always best to run speaker wires in steel conduit, mainly so you can make changes. I'm certain there will be a move to powered speakers. If you don't want to lay conduit, see if any 60 cycle noise gets into the negative feedback of the amp and is audible from the speakers. If the 60 Hz noise is audible, your only good solution is steel conduit.

 

[mtrycrafts]

I've read about running speaker cables to cross electrical lines at 90 degrees and to not run parallel to electrical in close proximity. In situations where you just can't avoid the closeness to electrical lines, what's a good way to insulate between the speaker cable and electrical cable to prevent interference? Does some thickness of wood or rubber or sheet metal work?

If you can find twisted speaker wires versus just parallel wires, that will help.
If you can do a test run before final sealing the wall, do that.

 

[mod]

Thanks for all the responses. I've already run 14/4 CL2 and 14/2 CL2 (from Monoprice) for the receiver to speaker runs. There are places where I had to run parallel to electrical lines for a couple of feet. I won't be able to test before the walls/ceilings are replaced. I was wondering if I should try to shield those places where I'm close to the electrical or just not worry about it. Sounds like it may not be an issue.

 

[mtrycrafts]

Thanks for all the responses. I've already run 14/4 CL2 and 14/2 CL2 (from Monoprice) for the receiver to speaker runs. There are places where I had to run parallel to electrical lines for a couple of feet. I won't be able to test before the walls/ceilings are replaced. I was wondering if I should try to shield those places where I'm close to the electrical or just not worry about it. Sounds like it may not be an issue.

You can tell from the wire if it is twisted inside the outer jacket. If they are, I would not worry. Besides, not sure how you would shield it otherwise from 60 Hz outside of the measures TLS suggested, steel pipe.
On the other hand, if you can place a steel conduit for the wire to be snaked through for that distance where it is in close proximity to the AC perhaps that may help too, not sure. At least, it would not be expensive to do or difficult.