Amp Wiring Kit: What Size Do You Need for a Sub?
An amp wiring kit is sized to the amplifier, not the subwoofer, so start with how much current your amplifier draws. Cable is sold by gauge, and a lower number means a thicker cable. As a rough guide, 8 gauge suits smaller amplifiers, 4 gauge suits most single subwoofer setups, and 2 or 0 gauge is for large amplifiers. The amplifier's manual gives the recommended size.
What is in a subwoofer wiring kit
- Power cable: the thick red lead from the battery to the amplifier.
- Inline fuse holder and fuse: protects the car if the power cable is ever damaged.
- Earth cable: a short lead from the amplifier to bare chassis metal.
- RCA signal leads: carry the sound from the head unit to the amplifier.
- Remote turn-on wire: switches the amplifier on and off with the stereo.
- Speaker wire, terminals and a grommet: to connect the sub and pass the cable safely through the firewall.
How to choose the gauge
Look at the amplifier's fuse rating or the cable size in its manual, then allow for the length of the run from the battery to where the amplifier sits. The longer the run, the thicker the cable needs to be. A cable that is too thin heats up and starves the amplifier, so the bass sounds weak and the amplifier can cut out. If in doubt, go one size thicker.
Copper or copper-clad aluminium?
Many cheaper kits use copper-clad aluminium (CCA), which carries less current than pure copper (OFC) of the same gauge. If a kit is CCA, choose a thicker size than the amplifier asks for, or use an OFC kit.
Where the fuse goes
The main fuse goes close to the battery, so the whole length of the power cable through the car is protected. Its rating should suit the cable, not only the amplifier. Power and signal leads are best run down opposite sides of the car to avoid engine whine. Wiring into a car's electrical system is easy to get wrong, so if you are not confident, have it done by a professional.
Have it fitted properly
We supply the right wiring kit and fit subwoofers and amplifiers at your home or work anywhere in Auckland: see subwoofer and amplifier installation. For a compact option, see under-seat subwoofers, and for the head unit side, how a stereo wiring harness works.
Frequently asked questions
Is 8 gauge enough for a subwoofer?
For a small amplifier or a powered under-seat sub, often yes. Larger amplifiers need 4 gauge or thicker. Check the amplifier's manual.
What happens if the amp wiring is too thin?
The cable heats up, the amplifier does not get enough current, the bass sounds weak and the amplifier may cut out or go into protection.
Do I need a fuse near the battery?
Yes. The main fuse should sit close to the battery so the whole power cable is protected if it is ever damaged.
Is a CCA wiring kit OK?
It can be, if you choose a thicker gauge to make up for it. Pure copper carries more current for the same size.