Speaker cable must be large-gauge to minimize resistance and preserve amplifier damping factor

Speaker cables carry high-current signals from the amplifier output to the loudspeaker. Unlike line-level cables, speaker cables are unshielded and must have low resistance. Cable resistance adds to the amplifier’s output impedance, reducing the damping factor — the amplifier’s ability to control loudspeaker cone motion electrically (damping factor = load impedance ÷ amplifier output impedance). High resistance cable raises effective output impedance, reduces damping, and allows the speaker cone to ‘ring’ after transients. For an 8Ω loudspeaker, less than 0.5 dB loss is the target; the handbook recommends minimum 14 AWG for typical runs, 12 AWG or larger for long runs to low-impedance loads. Inductance and capacitance in coaxial cables can create filter effects — parallel-conductor ‘zip cord’ is preferable for speaker use.

Examples

50 feet of 18 AWG cable at 4Ω nominal load produces approximately –2 dB loss and significant damping factor degradation. Replacing with 12 AWG reduces loss to under 0.5 dB.

Assessment

Why is a speaker cable’s role fundamentally different from a mic or line-level cable’s role? Why is shielding inappropriate for speaker cables?