"Safety" of speaker and power wire in same area

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JHZR2

JHZR2

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Hi,

Ive seen conflicting language on the "safety" of putting a power line and a speaker line in the same joist/stud run.

Is there a safety aspect to having the LV speaker line and "HV" romex? I'd love to put a 12Ga speaker line (2) in with one 14Ga romex that only runs a light.

Given that the speakers are low impedance loads, and Id only be pulling, say, 200W max, I dont see it as a big issue, but the fact that "safety" vise interference or "hum" or similar language makes me a bit worried.

The run would be in a corner run up the wall, essentially a box created by the outer plywood of the exterior wall, and two 2x6s making the other two corners.

Thoughts?

Thanks!
 
Needs to be rated CL-2 or CL-3 to be put in the wall. You could also put it in conduit where it crosses Romex in order to minimize the possibility of electrical interference.
 
My wire is FT2 rated, which is another lack of clarity, is that "good enough"? As I understand it, this is a "horizontal fire test".
 
COLEMAN CABLE E32389712 AWG 2/C UNDERGROUND LOW ENERGY CIRCUIT
CABLE SUNLIGHT RESISTANT 60C (UL) 150V -- C(UL) 30V FT2

FT2 is a fire/retardance spec, just like the in-wall CL2 and CL3 ratings... apparently.
 
Outside of the flame-spread rating of the cable (can't comment without knowing more about the cable), I don't see a safety problem.

There might be a "nuisance" issue on the speaker, but I think it's unlikely. Given the parallel geometry, there is an elevated amount of induction that will occur on the speaker line, so do try to keep them as far apart as possible. That said, speaker-level signals are pretty resistant to interference.

I have a joist in my crawlspace that has a 4 ft length with NM cable on one side and two speaker cables on the other, and I don't notice any problems on the speakers.

Edit: I saw that you added info about cable while I was writing the text above.
 
Last edited:
Thanks! Does shielding have to be metallic and grounded, or would the increase of a heavy insulator (like an 800V silicone sheath) over one or the other help?

Id imagine the magnetic field would not be effected by it, but at least there is a hard spacer between it in case the wires cross in wall.

I wonder if there is a metallic sheath that could be added and grounded...
 
You can also twist the speaker cable as it's installed to reduce hum pickup, which I doubt you'd hear anyway due to the low impedance of the speaker.

Is the cable you're using landscape lighting cable? Black stuff that looks like zip-cord?
 
That's what Im thinking, as it is UV protected, and relatively cheap for a 12ga run (I need to take it about 30ft through my basement then just a short run up the wall).
 
Originally Posted By: JHZR2
That's what Im thinking, as it is UV protected, and relatively cheap for a 12ga run (I need to take it about 30ft through my basement then just a short run up the wall).


You could use 12ga NM or UF for speaker wire. Nothing in the code prevents it. UF is also sunlight resistant.
 
If you have to run speaker and electrical wires parallel, keep them at least 12" apart to minimize noise interference (talking sound, not building code). If they cross, keep the angle at 90 degrees.

If you have not bought your speaker cable yet, check with a local sound supply company or online (PM me for links). You can get good quality speaker cable relatively cheap.
What's the rating on your speakers/amp?

I've dealt with enough buzz/radio interference in my sound systems that I won't use unshielded cables (not in metal conduits). And yes, you will hear the interference. If it is a mission critical installation (church, auditorium), you also want your sound system to be on a separate circuity breaker. Computer power supplies are notorious for feeding AC noise back into the lines which gets picked up by mixers and amps.

Put a QUALITY AC line conditioner into the system either way.
 
Originally Posted By: Stu_Rock
Here's the spec sheet:
https://www.ccixpress.com/wcsstore/CCIxpress/images/catalog/catalogPDFs/5-/55269.pdf
It is an SPT-style cable.

I'm a little uneasy about the flame-spread since this is a "riser" going between floors.


Right, but the FT2 is a flame retardance specification... What I dont get here is the difference between that and the other "C" specs which are OK for in-wall use.

FT2 should be self extinguishing per my reading of the spec.

I can pull whatever I want/need to at this point, I have this stuff which is nice stranded 12-ga, which I figure is good for the long run, regardless of what goes in-wall... And if I need to do two splices (may as well use this outside since it is OK for sunlight), I figure that is OK.
 
OK, so I'd go with the 12 ga wire through the house, twisted, then splice to in-wall rated (I assume it could be smaller gage for a short section of the run) then back to this 12ga stuff for the sunlight resistance.

Does that make sense?
 
I agree the horizontal portion is basically OK. I think the NEC CL ratings require vertical flame tests, which is why I have the concern about the vertical portion.

I'm not going to say not to use the cable. It's up to you to evaluate the hazard--for example, the flammability of the surrounding material and the presence of any sources of ignition.

Also, you could run the vertical portion (plus ~1 ft of horizontal) of the cable in smurf tube or in flame-rated vinyl-coated fiberglass tubing (the new stuff used for tubes in knob-and-tube). That's an easy thing to do, especially if the vertical portion is short. It's not exactly following spec, but it will retard flame just as well (or better).
 
Stu,

That is a good point. I have some of that fiberglass tubing from my knob and tube wiring, which may work well...

There are no ignition sources around, this is a 2x2 corner of the house... But there is an electrical wire in there running up to a light only... I guess extra insulation is key to make it right...

Thanks
 
Actually, now that I think about it, my wiring does the following:

Horizontally in the basement, up from the basement (above ground level) to the exit at the upper point on the first story wall.

There is no second story near where the wire will run vetically. The wire will also run horizontally in and out of the vertical run.

Since there is a horizontal run on both sides, and the "riser" is only in the single story, is this still an issue?

My biggest fear would be fire in the basement rising on the wire, and the run is horizontal there (and Id cover it with some of that fiberglass K&T covering as an added touch.

WOuld that be better? Seems that the vertical run may be a moot point, as there is nothing for the vertical flame to spread to. If there is fire in that riser, then the one story it is run in is already on fire. If there is fire adjacent to the vertical run, the wire is horizontal and would be covered by a secondary item.

Thanks!
 
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