Speaker wire and 110volt wire in fiberglass light pole

Rick S

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Jan 2021
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Florida
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We are installing 20 foot direct burial fiberglass light poles, and we are mounting speakers for a pa system on the pole about 12 feet up. Can the wires be run in the pole together if they are UF rated? And will the 110volts cause interference or static in the speakers?
 
#14 or #12 THHN makes perfectly serviceable speaker wire so that would eliminated the "mixed voltage" issue. As for interference, maybe. there are a lot of variables involved. I'm sure somebody makes a shielded wire that can be used of speakers. Google will be your best friend on that one.

Bubba
 
The 120VAC wiring will likely be powering LED lighting. This non-linear load could easily give you audible pops and clicks in your audio system. I would suggest you try test benching them by running out about 15 feet of 120V wire, wiring up one of the lights, and then running your speaker wire next to it.


Ideally, if you can maintain a few solid inches of separation, you should be okay, provided you are running separate conduits to the system. If you search for outdoor speaker wire, you will find a suitable setup.


In general, I strongly advice against direct-burial wire for all but the most basic and non-critical of tasks. Having a conduit there that new wire can be pulled through is not to be over-rated.
 
We are installing 20 foot direct burial fiberglass light poles, and we are mounting speakers for a pa system on the pole about 12 feet up. Can the wires be run in the pole together if they are UF rated? And will the 110volts cause interference or static in the speakers?

Most PA systems drive their speakers using a "100V Line" system with transformers. Either way, the characteristic impedance of the speaker system will be sufficiently low enough for it not to be affected by mains "noise". Also there will be no "grounding" of either speaker cable core, making it a "balanced" signal, so any induced current from the ac wiring will be cancelled out at the receiving end.

Does that change people's views on the subject.

I have never heard of any issues regarding crosstalk between mains cables and speaker cables, and very few installations even attempt to keep the two sets of wiring apart.


You could, of course, elect to use shielded cable for your PA speakers, making the job more expensive.

And if you are "direct burying" 110V ac cables, shouldn't those be armoured, providing another way of shielding.

EDIT : In any case, if the speaker cables run anywhere near the 110V ac cables, they must have a voltage rating equivalent to, or greater than, the rating of the 110V circuit.

2nd EDIT : I believe that if you separated the buried cables by 100mm, which can be done either side-by-side, or "over-under", depending on the width of your trench, you will eliminate the possibility of any "substantial" pickup. The 12ft runs inside the poles would be less significant, and probably negligible. And if you can maintain some degree of separation, even better, depending on the pole diameter. Even if you can only get 10 mm, that would be better than none. Don't forget that you will only need 1 cable to each PA speaker, use insulated junction boxes below ground level. Otherwise you'd have to run two, loop-in, loop out.
 
Last edited:
Most PA systems drive their speakers using a "100V Line" system with transformers. Either way, the characteristic impedance of the speaker system will be sufficiently low enough for it not to be affected by mains "noise". Also there will be no "grounding" of either speaker cable core, making it a "balanced" signal, so any induced current from the ac wiring will be cancelled out at the receiving end.

Does that change people's views on the subject.

I have never heard of any issues regarding crosstalk between mains cables and speaker cables, and very few installations even attempt to keep the two sets of wiring apart.


You could, of course, elect to use shielded cable for your PA speakers, making the job more expensive.

And if you are "direct burying" 110V ac cables, shouldn't those be armoured, providing another way of shielding.

EDIT : In any case, if the speaker cables run anywhere near the 110V ac cables, they must have a voltage rating equivalent to, or greater than, the rating of the 110V circuit.

2nd EDIT : I believe that if you separated the buried cables by 100mm, which can be done either side-by-side, or "over-under", depending on the width of your trench, you will eliminate the possibility of any "substantial" pickup. The 12ft runs inside the poles would be less significant, and probably negligible. And if you can maintain some degree of separation, even better, depending on the pole diameter. Even if you can only get 10 mm, that would be better than none. Don't forget that you will only need 1 cable to each PA speaker, use insulated junction boxes below ground level. Otherwise you'd have to run two, loop-in, loop out.


UF cables in the US just have a very stiff sheathing, and not much structural protection. As far as crosstalk, I've seen it on a remote call system a year or so ago, so I pay more attention now. I'm far from an expert, I just don't want to deal with it again.
 

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