What Is the Big 3 in Car Audio?

The Big 3 upgrade involves adding thicker cables to three key connections in your vehicle’s charging and grounding system.

It helps reduce electrical resistance and voltage drop when an aftermarket amplifier places extra demand on the system.

Which Three Connections Are Upgraded?

The typical Big 3 upgrade covers the following power and ground connections:

1. Alternator Positive to Battery Positive

This cable carries charging current from the alternator to the battery. Adding a thicker cable helps reduce resistance and voltage drop along the charging path.

2. Battery Negative to Chassis

This ground cable connects the battery’s negative terminal to the vehicle’s body or frame. Upgrading it helps provide a low-resistance return path for electrical current.

3. Engine Block to Chassis

This connection provides a ground path for the engine and the alternator mounted to it. A suitable ground connection is just as important as the positive cable supplying power.

The exact grounding arrangement can vary between vehicles, so the installation should suit your car’s electrical system.

Why Upgrade the Wiring?

Factory wiring is designed around the vehicle’s original electrical equipment. Adding powerful amplifiers and subwoofers increases current demand, which can expose restrictions in the charging cables and ground connections.

“From our experience with car audio installations, a Big 3 upgrade can be worthwhile when a high-powered amplifier is placing significant demand on the vehicle’s electrical system. Properly sized power and ground cables can help minimise voltage drop and provide a more stable electrical supply to the audio system.” – AEP Audio Melbourne.

Larger cables reduce resistance in those paths, helping maintain voltage under load. Potential benefits include:

• Reduced voltage drop when the audio system draws high current.
• Less headlight dimming during heavy bass.
• A more stable electrical supply to your amplifier.

However, the Big 3 does not increase your alternator’s output. If your audio system demands more power than the alternator can supply, you may still need an alternator or battery upgrade.

What Cable Does a Big 3 Upgrade Use?

Common options include 4 AWG and thicker 1/0 AWG cable, with the appropriate size depending on current demand and cable length. Quality oxygen-free copper cable is commonly used.

The upgrade cables are generally added alongside the factory wiring, leaving the original connections intact.

Is the Big 3 Worth Doing?

If you’re installing a high-powered audio system or experiencing voltage drop, the Big 3 is worth considering as part of an electrical assessment.

Secure connections, suitable fuse protection and correct cable routing all matter. Vehicles with battery-monitoring systems may also need a different grounding approach, so have an auto electrician or experienced car-audio installer assess your setup.