When running power and ground cable for car audio systems, it
is strongly recommended that you replace all of the following
lines with larger gauge cable:
motor to chassis ground
alternator to battery positive terminal
battery negative terminal to chassis ground
battery positive terminal to amplifiers or distribution block
amplifier(s) to chassis ground
power and ground cables:
For a reference chart to determine wire size based on distance
run and current draw or wattage, see here:
Power and
Ground cable chart
For actual wire diameter based on American Wire Gauge (AWG) see
here:
American Wire
Gauge Sizes
These charts only go up to 2AWG,
but the logical progression to 1/0, 0, and 00 gauge should be
obvious.
For more information on wire and
it's applications in car audio, see here:
Badic Car Audio and Electronics
Speaker wire sizing:
Speaker wire isn't as vital as power and ground, because you're
dealing with high voltage, low current AC voltage for speakers,
much like wall outlets in a house, as opposed to high current
DC voltage for power and ground.
Generally, this is my rule of thumb:
for component speakers (midbass, midrange, or tweeters) 18-16AWG
is fine.
For subwoofers, 14-12AWG is plenty.
Anything you choose to use of a larger gauge will really only
be for looks, as there will be no electrical advantage to larger
wire.
