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I'm hooking up a couple of small speakers (3w max each) outside, and I have a small run in my house from inside to out that was done with ethernet cable. There's no way I can pull speaker wire through, I need to use the ethernet for about 15 feet. I'll run heavy gauge speaker wire from the amplifier to ethernet cable, and then speaker to ethernet cable (both those runs are short, 5 feet or so).

What is the best way to use the ethernet cable (23 gauge cat6)?

Should I join each twisted pair together and treat it as 4 wires (one each for positive and negative times 2 speakers)?

Should I take one wire from two pairs (eg white-green, white-orange together are positive for one speaker, green and orange are negative)?

Should I just use two twisted pairs total and leave the others unused?

I know I need to keep the resistance down but I'm not sure of any capacitive effects are going to interfere, or what's best overall.

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  • \$\begingroup\$ Use two standard 70V audio transformers, one at the amp to boost and another at the speaker to bring it back down. Works great. 70V and higher is used in commercial applications all the time and parts are not that expensive. \$\endgroup\$
    – Gil
    Jun 30, 2021 at 1:26

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You can ignore cable capacitance effects at audio frequencies for speaker wiring.

Inductive coupling could be noticeable but not over that distance.

Just use as much copper as you can to keep the resistance down.

One way is to parallel up the two wires in each pair so you now have four separate wires. Use two for each channel.

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    \$\begingroup\$ I wonder if you could even multiplex ethernet on top of this, using something like a PoE injector to inject the audio signal as a common-mode signal between two pairs. \$\endgroup\$
    – Hearth
    Jun 29, 2021 at 18:14
  • \$\begingroup\$ @Hearth - yes you probably could. I don't know whether the inductors normally in a PoE injector would support enough current but they may. \$\endgroup\$ Jun 29, 2021 at 23:27
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It's hard to say anything for sure without knowing your amplifier, but you can use this chart to figure out how much wiggle room you have on the current: https://www.engineeringtoolbox.com/wire-gauges-d_419.html

Figure out how much current your amplifier is rated to put out, then make sure you're using enough CAT5 conductors to match that. Your existing speaker wire can be a reference point if your amplifier manual doesn't clearly specify its output current.

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