Speaker wire
Thicker wires reduce resistance. The resistance of 16-gauge or heavier speaker connection cable has no detectable effect in runs of 50 feet (15 meters) or less in standard domestic loudspeaker connections for a typical 8 ohm speaker. As speaker impedance drops, lower gauge (heavier) wire is needed to prevent degradation to damping factor – a measure of the amplifier's control over the position of the voice coil.
Insulation thickness or type also has no audible effect as long as the insulation is of good quality and does not chemically react with the wire itself (poor-quality insulation has occasionally been found to accelerate oxidation of the copper conductor, increasing resistance over time).
High-power in-car audio systems using 2-ohm speaker circuits require thicker wire than 4 to 8-ohm home audio applications.
Most consumer applications use two conductor wire. A common rule of thumb is that the resistance of the speaker wire should not exceed 5 percent of the rated impedance of the system. The table below shows recommended lengths based on this guideline:
| Wire size | 2 Ω load | 4 Ω load | 6 Ω load | 8 Ω load |
|---|---|---|---|---|
| 22 AWG (0.326 mm2) | 3 ft (0.9 m) | 6 ft (1.8 m) | 9 ft (2.7 m) | 12 ft (3.6 m) |
| 20 AWG (0.518 mm2) | 5 ft (1.5 m) | 10 ft (3 m) | 15 ft (4.5 m) | 20 ft (6 m) |
| 18 AWG (0.823 mm2) | 8 ft (2.4 m) | 16 ft (4.9 m) | 24 ft (7.3 m) | 32 ft (9.7 m) |
| 16 AWG (1.31 mm2) | 12 ft (3.6 m) | 24 ft (7.3 m) | 36 ft (11 m) | 48 ft (15 m) |
| 14 AWG (2.08 mm2) | 20 ft (6.1 m) | 40 ft (12 m) | 60 ft (18 m)* | 80 ft (24 m)* |
| 12 AWG (3.31 mm2) | 30 ft (9.1 m) | 60 ft (18 m)* | 90 ft (27 m)* | 120 ft (36 m)* |
| 10 AWG (5.26 mm2) | 50 ft (15 m) | 100 ft (30 m)* | 150 ft (46 m)* | 200 ft (61 m)* |
* While in theory heavier wire can have longer runs, recommended household audio lengths should not exceed 50 feet (15 m).
The gauge numbers in SWG (standard wire gauge) and AWG (American wire gauge) reduce as the wire gets larger. Sizing in square millimeters is also common outside of the US. Suppliers and manufacturers often specify their cable in strand count. A 189 strand count wire has a cross-sectional area of 1.5 mm2 which equates to 126.7 strands per mm2.