Speaker cable thickness is measured in AWG (American Wire Gauge), and the numbers run backward: a lower number means a thicker wire. The right gauge depends on two things, how long the run is and the impedance of the speaker. Too thin a cable wastes power as heat and weakens the amplifier’s control over the speaker.
Why gauge matters
Every wire has resistance, and thinner or longer wire has more of it. That resistance is in series with the speaker, so some of the amplifier’s power is lost in the cable instead of reaching the speaker. A common rule of thumb is to keep the total resistance of the cable, out and back, under about 5 percent of the speaker’s impedance.
The chart
This table shows the longest run that stays within that 5 percent guideline for pure copper cable. It is calculated from standard resistance values for copper wire, and it counts both conductors, since the signal goes out and comes back.
| Gauge (AWG) | 8 ohm speaker | 4 ohm speaker | 2 ohm speaker |
|---|---|---|---|
| 18 | about 30 ft | about 15 ft | about 8 ft |
| 16 | about 50 ft | about 25 ft | about 12 ft |
| 14 | about 80 ft | about 40 ft | about 20 ft |
| 12 | about 125 ft | about 60 ft | about 30 ft |
Lower impedance speakers draw more current for the same power, so they need thicker cable or shorter runs. If you connect several speakers to one output, work out the total impedance first. Two 8 ohm speakers in parallel present 4 ohms.
Practical advice
- Short runs, 10 feet or less: 16 AWG is plenty for almost any 8 or 4 ohm speaker.
- Typical stage runs, 25 to 50 feet: 14 AWG is a safe default. Use 12 AWG for 4 ohm loads or powerful rigs.
- Long runs beyond 100 feet: use 12 AWG or thicker, and think about whether powered speakers with line-level cabling would be easier.
- When in doubt, go one gauge thicker. A cable that is thicker than needed costs a little more and weighs more. It never causes a problem.
Cable material matters too
The chart assumes pure copper. Copper-clad aluminum (CCA) cable is cheaper and lighter but has higher resistance for the same gauge, so use a thicker one or a shorter run. Check the packaging for what the conductor is made of.
Connectors
Speaker cables end in 1/4 inch TS plugs, Speakon connectors, or banana plugs. Speakon locks in place and carries more current safely, which is why it is common on professional PA gear. Whichever you use, never put a speaker output through an instrument cable. See speaker cable vs instrument cable.