Quick Answer / Summary: Match gauge to run length and speaker impedance: 16 AWG is fine to about 15 m for 8 ohm speakers, 14 AWG to about 24 m, and 12 AWG beyond that; halve those distances for 4 ohm loads. Use oxygen-free copper rather than copper-clad aluminium, choose CL2 or CL3 rated cable for in-wall runs, and keep both conductors the same length and type.
Loudspeaker wire is a power cable carrying an audio-band signal, so the only electrical properties that matter are resistance, inductance and capacitance. Gauge and length set the first, construction sets the rest, and marketing sets the price.
Why Resistance Is the Whole Argument
The amplifier sees the speaker impedance in series with the cable resistance. A long thin cable adds enough resistance to reduce damping and to waste power as heat, which shows up as loose bass rather than as an obvious fault.
The usual rule is to keep total loop resistance below about 5 percent of the speaker impedance. For an 8 ohm speaker that is 0.4 ohm, which a 16 AWG run reaches at roughly 15 m and a 14 AWG run at roughly 24 m.
4 ohm loads halve the distance
Lower impedance makes the same cable resistance a bigger fraction of the total. A run that is comfortable with 8 ohm speakers needs one gauge larger for 4 ohm speakers.
Damping factor
Damping describes how well the amplifier controls cone movement. Cable resistance lowers it. In practice, gauge matters more than the amplifier’s headline damping figure once the run passes 10 m.
Copper, CCA and Plating
Oxygen-free copper is the default. Copper-clad aluminium has roughly 60 percent of copper’s conductivity, so a CCA cable must be about two gauges larger to match an OFC cable, and it work-hardens and breaks more readily at terminations.
Silver plating helps at high frequencies and in connector contacts, not in the bulk conductor at audio frequencies. For loudspeaker runs, it is a durability choice rather than a sound quality one.
Strand count
More, finer strands make the cable more flexible and more resistant to fatigue in moving installations. For fixed runs, strand count is a handling preference, not an electrical requirement.
Terminations
A poor connection adds more resistance than the cable. Solder or crimp properly, tighten binding posts by hand, and re-check after a month because copper creeps under pressure.
Insulation and Ratings
In-wall and ceiling runs need a jacket listed for the space: CL2 for general in-wall, CL3 for higher voltage and commercial, and plenum-rated where the cable runs in an air-handling ceiling.
Outdoor runs need UV-resistant jacket and a direct-burial rating if buried. Standard PVC jacket cracks in sunlight within a season or two.
Polarity
Keep the stripe or the printing on one conductor consistent at both ends. A reversed speaker still makes sound, with weak bass and a shifted image that is easy to blame on the room.
Length matching
Left and right runs should be the same length and gauge. Unequal resistance shifts the image slightly and complicates troubleshooting.
Gauge by Run Length
Approximate maximum run for a loop resistance below 5 percent of the load.
| Gauge | 8 ohm run | 4 ohm run | Typical use |
|---|---|---|---|
| 18 AWG | About 10 m | About 5 m | Short desktop runs |
| 16 AWG | About 15 m | About 8 m | Bookshelf speakers |
| 14 AWG | About 24 m | About 12 m | Home theatre, in-wall |
| 12 AWG | About 36 m | About 18 m | Long runs, 4 ohm loads |
| 10 AWG | About 55 m | About 28 m | Large rooms, subwoofers |
Real Installations
Two typical jobs and the gauge decision behind each.
Living room with in-wall runs
A 12 m run to surround speakers is comfortable on 14 AWG CL2 cable. Leave a service loop at both ends, label the polarity, and terminate on a wall plate rather than pushing bare wire into a ceiling speaker.
Outdoor patio speakers
Use UV-rated 14 AWG with a direct-burial jacket, run it in conduit under paving, and leave a drip loop at the wall entry. Seal the wall penetration and keep the amplifier end indoors.
Frequently Asked Questions
Does thicker speaker wire sound better?
Only when the run is long enough for resistance to matter. Below about 10 m with 8 ohm speakers, 16 AWG is electrically indistinguishable from 12 AWG.
Can I use CCA speaker wire?
It works for short runs, but it has higher resistance and corrodes more readily at terminations. Use OFC for anything permanent.
Can I run speaker wire next to mains cable?
Avoid long parallel runs. Cross at right angles if you must, and keep at least 300 mm of separation to reduce induced hum.
Do I need CL2 or CL3 rated cable?
Yes for in-wall or ceiling installation, because the jacket listing is a fire code requirement, not a marketing feature.
What happens if I reverse polarity?
The speaker still plays, but bass cancels and the stereo image collapses. Check the stripe at both ends before blaming the electronics.
Related resources: passive speaker cable; 2 conductor speaker wire; speaker wire with plugs