Extending a speaker cable.

Jay Barracato

Jay Barracato

Graduate Student
Jan 11, 2011
1,528
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38
Solomons MD
What is your preferred method for an inline splice to lengthen an installed speaker cable.

I am moving a pair and it is not feasible to do a new home run to the amps. The cable is in the open at the speaker end.

Sent from my XT1254
 
Re: Extending a speaker cable.

If the location is accessible for you to make the splice and it is somewhat protected from physical damage, I would solder and heat shrink. That keeps the form factor of the cable and is unlikely to fail unless physically disturbed.
 
Re: Extending a speaker cable.

Rob Timmerman said:
Your options may be limited by the power rating of the amplifiers. Do you know if the output from the amplifiers is considered power limited (Class 1, 2, or 3)? If not, you will need to perform a splice appropriate for mains voltage.
Click to expand...

I was thinking TJ's solution. When you say for mains voltage I think box with clamps and wire nuts. Is that what you mean?

The splice will be up in the metal rafters so unaccessible and unlikely to be disturbed.

Sent from my XT1254
 
Re: Extending a speaker cable.

Jay Barracato said:
What is your preferred method for an inline splice to lengthen an installed speaker cable.

I am moving a pair and it is not feasible to do a new home run to the amps. The cable is in the open at the speaker end.

Sent from my XT1254
Click to expand...

There a few options.

Wire nuts

Wire crimps

Twist and tape

Solder splice

Note, if you choose to solder the wire, do not use a mechanical connection such as a crip or wire nut, as that can cause fractures in the solder, leading to a potentially failed connections.

All will be about the same as far as reliability as long as the wire is not under stress or moving, so choose what's the most convenient for you.
 
Re: Extending a speaker cable.

I would probably use a regular 4x4 metal electrical box with a blank cover and a couple romex connectors to bring the two wires into the box.

Then once inside, I'd just use an appropriately sized wire nut to make the splice for each conductor. Once properly installed, wire nuts are pretty robust.

Be sure to sharpie on the cover of the box that it is a loudspeaker circuit and what it is for. I wouldn't want an electrician coming along later and thinking that he should wire power into that box from somewhere...
 
Re: Extending a speaker cable.

Chuck Simon said:
Really, a junction box for a speaker cable? I hope you never have to pull that cable.
Click to expand...
Junction boxes may be required by the local AHJ, and the NEC basically treats Class 1 wiring (typical for the outputs of power amplifiers) as power wiring (with certain differences involving allowable wire sizes and how conduit fill is calculated). So an appropriate splice (Listed crimps or compression connectors [wire nuts]) in a standard box is the correct way to do this. Low voltage boxes may be OK if they are listed for use with Class 1 circuits, but most that I've seen are for Class 2 circuits only. This matters, because Class 1 circuits have enough energy to pose a fire risk, while Class 2 circuits do not.

Go back and reread Articles 640 and 725 of the NEC (and chapter 3, since it is referenced by Article 725 for Class 1 wiring).
 
Re: Extending a speaker cable.

Well it turns out the cables were coming from the opposite directions than I thought, so I ended up taking up a handful of coils with a cable tie.

Sent from my XT1254
 
Re: Extending a speaker cable.

Do many amps have a "use Class 1 cable" sticker on the back?
In which case, use normal voltage plastic junction boxes.
One of the reasons for junction boxes is to make cable pulls easier.
 
Re: Extending a speaker cable.

Kevin Graf said:
If you are using a junction box (which has it's advantages) then a plastic box or a low voltage plastic box will be fine.
Click to expand...

A normal plastic (PVC) junction box and cover would be my choice as well. If wire nuts appropriate to the wire size are fine for AC, I see no problem using them for speaker audio. The spring tension they provide gets around that nasty problem of having to periodically tighten screw connections.

If you use metal, it has to be bonded to ground, even if there is only low voltage inside. This is a code requirement (at least it is in Canada, and I suspect in the NEC as well).

GTD
 
Re: Extending a speaker cable.

Butt splice appropriate size for the wire. Crimp in place and shrink over it. Shrink over the whole thing if you need to worry about pulling the cable anywhere. That'll keep your profile the smallest. It's got the added benefit of being easy to do when working in tight spaces.
 
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