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I removed a blank two-gang wall plate from my wall to see what was behind it. I found this:

enter image description here

What are these? Speaker wires? I'd love to cover this hole in the wall over with drywall, but I have a feeling people are going to tell me not to do that.

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    Since it's just a low-votage ring, not a junction box, you can plug it if you want to. Unclear what great aesthetic benefit that carries, given you have an outlet 6" from it, but suit yourself, on this one.
    – Ecnerwal
    Oct 30, 2022 at 18:05
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    These do look a lot like speaker wires. But lamp cord can look the same. And somebody did permanently wire a light with lamp cord inside the wall on a house I used to live in. I recommend tracing and finding the other end of these wires before burying them. Oct 30, 2022 at 18:42
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    I'd suggest pulling the cover off the other box in the picture to see if the other end of this wire happens to be in that box. You never know...
    – FreeMan
    Oct 31, 2022 at 15:07
  • I agree with @Ecnerwal and I'll add: I'm not sure that's even drywall you have there. There's a lot of texture. It'll be hard to match. Getting a cover to match the adjacent one will not only be easier, it'll look better.
    – jay613
    Oct 31, 2022 at 15:19
  • Presumably you touched them or touched them together and nothing happened. I'd be using a multimeter on each pair, first to find any voltage, and if not, to find any resistance. If they're speaker wires (highly likely) then they could show a resistance of around 4-8 Ohms.
    – Tim
    Oct 31, 2022 at 15:20

5 Answers 5

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Approved for In-Wall?

Those are speaker wires and, going by appearance and the transparent jacket, they might not be fire rated. Most transparent PVC jackets are not rated, some could be.

Check the black writing on the jacket (near your thumb in that picture).

As is often overseen, in wall wiring must have a CL/CP or FR fire rating. If the wire runs through an air return duct or an air return wall space, a.k.a. a "plenum", then a higher "plenum" rating is required.

If it is not rated, closing it up and not using it unfortunately does not resolve the non-compliance. Best if you can pull it out.

This may very well be an issue that would not pass inspection, but once discovered behind a wall is not serious enough to require remediation.

Here's an overview of the pertinent labeling:

In-Wall

In-Wall: Usually in reference to an "in-wall rated" cable which is designed to be installed inside a wall safely. Cables that are in-wall rated need to have a designation printed on the cable jacket showing exactly what its rating is. These ratings are generally flammability related. CL2 and CL3 are commonly seen on standard in wall rated cables such as HDMI cables or Audio Video cables. There are also higher rated designations such as CM, CMR and CMP. If a CL2 rated cable is required for an installation, a higher rated cable can always be used in its place.

CL2

CL2: This is a cable jacket fire resistance rating defined in Article 725 of the National Electric Code. It stands for "Class 2 Remote-Control, Signaling, and Power-Limited Circuits" cable, which indicates that the cable is suitable for in-wall installation and use for certain low-voltage applications. Examples of Class 2 circuits include burglar alarm cabling, intercom wiring, and speaker wire. The jacket is designed to protect against voltage surges of up to 150 volts. CL2 cables may be further classified as "CL2R" (Riser Rated) and CL2P (Plenum Rated). For a more detailed explanation of Riser and Plenum ratings, see "CMR" and "CMP" below.

CL3

CL3: CL3 stands for "Class 3" wire and is also defined in Article 725 of the National Electric Code. Broadly speaking, it mirrors the definitions of Class 2 wire, but the jacket is designed to protect against voltage spikes of up to 300 volts.

CMP

CMP: This is a cable jacket fire resistance rating defined in Article 800 of the National Electric Code. It stands for "Communications Multipurpose Cable, Plenum", which indicates that the cable is suitable for installation in a plenum space. Because air travels throughout a building via plenum spaces, it is critical that cables that are installed in such spaces not give off toxic smoke when they burn. Thus, plenum-rated cables are designed using materials that burn more cleanly and self-extinguish more easily. As the flammability requirements for Type CMP cables are stricter than Type CM and CMR cables, Type CMP cables can be used as a substitute in any area where CM and CMR would be required. Cables that are labeled "Type CMP" must pass a standardized flammability test and be certified by an accredited laboratory, such as Underwriters Laboratories (UL).

CMR

CMR: This is a cable jacket fire resistance rating defined in Article 800 of the National Electric Code. It stands for "Communications Multipurpose Cable, Riser", which indicates that the cable is suitable for use in a "riser" installation, meaning, it can be installed vertically between stories of a commercial building. The goal of a riser-rated cable is to be flame-retardant enough to prevent the spread of fire from one floor to another. In that respect, it is more flame-retardant (and consequently, more expensive) than type CM cable, although not as much as type CMP cable (see CM, CMP). As the flammability requirements for Type CMR cables are stricter than Type CM cables, Type CMR cables can be used as a substitute in any area where Type CM would be required. Cables that are labeled "Type CMR" must pass a standardized flammability test and be certified by an accredited laboratory, such as Underwriters Laboratories (UL).

From: https://www.cablewholesale.com/support/technical_articles/confusing_cable_terms.php

This is an example of proper and legal in-wall speaker wire:

enter image description here

From: https://www.crutchfield.ca/g_22112/In-wall-Speaker-Wire.html

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    Very useful write up. Bookmarked!
    – FreeMan
    Nov 1, 2022 at 15:33
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Check that the wires are not carrying any house current. If not, then you may proceed as you wish. DO NOT attach a battery before checking for house current.

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    Excellent answer! This is, in fact, speaker wire. I have seen homes where some "happy homeowner" has used this type of wiring to power a light bulb, clock, etc. ALWAYS verify the wires have no current!!!!
    – Scottie H
    Oct 31, 2022 at 18:24
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Yes, those are speaker wires. A number of comments have noted that they might be connected to power anyway, so checking thoroughly - either to find the other end, if possible, or at least using a non-contact voltage tester to make sure they are dead - is a good idea.

If there are no 120V or 240V wires involved, you can cover this up with drywall. But before doing that, you may want to trace out the speaker wires to see if the box, using the speaker wires to pull new wires, might be useful for ethernet or other wires.

Patching/painting is definitely an option. Painting the blank plate to match the wall color would be a lot less work, though if you are planning to paint the entire room soon then patch/paint makes more sense.

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  • Yes. Investigate the potential for using the duct for other purposes. Otherwise board up with some suitably cut piece of plasterboard/ply about 1/8" behind wall plane. Then skim over with some filler before painting to match wall.
    – Trunk
    Oct 31, 2022 at 12:48
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    Yes, they look like speaker wires, but who knows what has been attached to them - don't assume that they are benign just from appearance.
    – MikeB
    Oct 31, 2022 at 14:38
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    Para 2: "Since there are no 120v..." should read "If there are no 120V...". Critically important to confirm that before moving ahead with covering it over. You never know what someone may have done.
    – FreeMan
    Oct 31, 2022 at 15:07
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    If you do cover these up, I recommend cutting off the ends first so that there is no non-insulated copper exposed. It'll be difficult to find them again once the hole is patched, and trimming them will reduce the likelihood that you'll ever need to do so.
    – bta
    Oct 31, 2022 at 23:44
  • Pardon my ignorance but, why is a non-contact voltage tester specified? Wouldn't a regular multimeter work to see if there is any voltage between those two wires, indicating if there is any power or not going to them?
    – cr0
    Nov 1, 2022 at 12:57
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You got it right, those are speaker wires. You could tap a 1.5V battery on them to hear if they run to a hidden speaker (you'll hear a pop).

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    Those could be speaker wires. Or they could be a lamp power cord that somebody ran through the wall when they shouldn't have. When dealing with non-standard wiring, making assumptions about function based on appearance can be deadly.
    – Mark
    Oct 31, 2022 at 21:44
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Your safest bet is to remove these wires before patching the hole. If these are indeed intended for speakers like they appear to be, then removing them shouldn't be too difficult.

These sorts of speaker connections are typically used for speakers that either mount high on the wall or recessed into the ceiling. If you have no speakers in those locations and don't see anything that might look like a cover for the other end of the wires, there are decent odds that the other end isn't connected to anything either. Very slowly and gently pull the wire out of the wall and see if the entire thing comes out. Stop if you feel resistance. The use of a blank cover instead of an actual wall jack makes me think this is not a professional installation, so I'd wager the wires are just dangling inside the wall cavity and aren't anchored anywhere.

If you have easy access to the attic space just above this room, it may be easier to trace the wire and remove it from up there.

Should you decide that you want to leave the wires in place just in case someone wants to use the speakers in the future, you can replace the blank wall plate with a speaker wall jack. That looks much more "intentional" than a big blank cover plate, and you for two wires you can shrink the opening down to a single gang. A wall jack like that also clearly says "this is for speakers", so future residents won't have the same confusion you're currently experiencing.

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