Speaker wire gauge depends on three factors: speaker impedance (typically 4Ω or 8Ω), distance from the amplifier, and power level. Thicker wire reduces resistance losses — especially important for long runs and low-impedance speakers.
For most home setups with 8Ω speakers under 50 feet: 16 AWG is fine. For 4Ω speakers or runs over 50 feet: 14 AWG. For subwoofers or runs over 100 feet: 12 AWG. For professional PA or very long runs: 10 AWG. The goal is to keep total cable resistance under 5% of the speaker impedance.
Speaker wire resistance creates a voltage divider with the speaker's impedance. If a 50-foot run of 18 AWG has 0.64Ω total resistance (both ways) and the speaker is 8Ω, that's 8% of the signal lost as heat in the wire. The same run with 14 AWG drops to 0.25Ω — about 3% loss.
Standard CCA (copper-clad aluminum) speaker wire is fine for most installations. OFC (oxygen-free copper) has marginally lower resistance and better corrosion resistance, worth it for permanent installations or outdoor runs. 'Monster cable' and other premium brands offer no measurable improvement over standard OFC at audio frequencies.
For in-wall installation, use CL2 or CL3 rated speaker wire (fire-rated jacket). 14 AWG CL2 is the most popular for in-wall home theater. For outdoor runs, use direct-burial rated cable or run standard wire through conduit.
Disclaimer: This guide is for informational purposes only. Always consult a licensed electrician and follow local building codes for actual installations. Wire sizing depends on specific conditions including ambient temperature, conduit fill, and derating factors.