How To Wire a Bridgable Car Stereo Amp

by David Lipscomb Google

    Your stereo amplifier provides solid two-channel stereo sound to components or coaxial speakers. However, if you choose to expand your stereo system and add a subwoofer, bridging that stereo amp is a proven way to extract more power and suitably drive the new speaker. Although the process is simple, you must make sure wiring polarity is correct to ensure safe and good-sounding results.

    Step 1

    Turn off the stereo system and vehicle.

    Step 2

    Unscrew the speaker wires attached to the stereo amplifier, using the appropriate screwdriver.

    Step 3

    Cut a new length of speaker wire sufficient to reach from the amplifier's location to the subwoofer or other speaker.

    Step 4

    Strip 1/2 inch of insulation from both ends of the new wire. Split the two conductors of the wire using your fingers. Ensure each conductor can comfortably span the speaker's binding post terminals at one end, and the left positive and right negative speaker output terminals on the amplifier.

    Step 5

    Slide the speaker wire conductor featuring printing or a molded ridge into or under the amplifier's left positive terminal. Tighten down this terminal with the appropriate screwdriver. Repeat for the unmarked conductor.

    Step 6

    Press down on the subwoofer's positive binding post terminal, typically marked with a red label. Insert the printed or molded speaker wire conductor into this terminal, then release it to secure to the wire. Repeat for the other conductor into the black or negative binding post terminal on the subwoofer.


    • Expect to have to adjust your amplifier gain to accommodate the new wiring scheme and different power handling needs of the new speaker.
    • Use the thickest gauge wire at the shortest possible lengths to maximize power transfer between the amplifier and speaker. Twelve and 14 gauge (AWG) speaker wire is normally appropriate.
    • If bass is very thin or nonexistent, make sure the polarity at the subwoofer and amplifier is the same.


    • Ensure all exposed speaker wire is safely secured under or inside its terminal, both at the amp and speaker. This prevents stray wire filaments from causing an accidental short circuit.
    • Do not use a subwoofer rated at less than 4 Ohms when bridging. Amplifier damage, repeated activation of thermal protection or blown fuses may otherwise result.

    Required Items

    • Speaker wire
    • Wire strippers
    • Screwdrivers (Phillips, Allen, Torx)

    About the Author

    David Lipscomb is a professional writer and public relations practitioner. Lipscomb brings more than a decade of experience in the consumer electronics and advertising industries. Lipscomb holds a degree in public relations from Webster University.

    Photo Credits

    • Matthew Peyton/Getty Images Entertainment/Getty Images