Speaker wire and cable carries amplified audio from an amplifier to loudspeakers. Although the signal is lower frequency than data or RF, conductor resistance, run length, speaker load and installation environment still matter. Properly sized speaker cable helps preserve amplifier damping, output level and system reliability.
Commercial and installed-audio systems may also require in-wall, plenum or multi-conductor constructions. Selection should account for conductor gauge, copper quality, polarity identification, jacket rating and whether the system is low-impedance or transformer-distributed.
Longer speaker runs and lower-impedance loads benefit from larger conductors because cable resistance becomes a larger percentage of the speaker circuit. 12, 14, 16 and 18 AWG are common sizes. The appropriate gauge depends on distance, speaker impedance and acceptable loss rather than on amplifier wattage alone.
Conventional 4- or 8-ohm speakers draw relatively high current. Cable resistance can reduce delivered power and alter damping, especially on long runs. Keep resistance small relative to speaker impedance. Multiple speakers connected in series or parallel also change the total load seen by the amplifier.
Commercial distributed systems use transformers at speakers so many devices can share long cable runs efficiently. Cable sizing is based on total power, line voltage, distance and allowable voltage drop. Speaker transformer tap settings must also be totaled so the amplifier has adequate capacity.
Most single-channel speaker circuits use two conductors, but four-conductor cable can support stereo pairs, bi-amp wiring or two nearby speaker circuits in one jacket. Multi-conductor designs can simplify pulls but require careful labeling so polarity and zones remain clear.
Maintaining consistent polarity prevents speakers from operating out of phase with each other, which can reduce bass and create uneven coverage. Use conductor markings consistently and document terminations. Avoid damaging insulation with staples or tight bends, and provide suitable strain relief at equipment.
In-wall, riser and plenum installations may require specific fire-rated jackets. Outdoor or damp locations require cable designed for moisture and sunlight. Speaker cable intended only for portable indoor use should not be substituted for permanent building wiring where code-rated cable is required.
Determine speaker system type, impedance or distributed line voltage, total load, run length, pathway rating and number of conductors. Then select gauge and construction with suitable margin. For commercial projects, coordinate cable rating with the building pathway and local code requirements.
Expensive oversized cable is not automatically necessary; correct gauge for resistance and distance is what matters. Speaker polarity should remain consistent even though the signal is AC. 70V systems use different load calculations from 4- or 8-ohm systems. Jacket rating is independent of conductor gauge.
Wallco can help compare specifications, compatibility and application requirements when you are selecting new components or replacing an existing part. Providing the manufacturer and model of the equipment you are connecting to, along with key electrical, mechanical and environmental requirements, helps narrow the correct choice.
