How to connect a subwoofer to a car stereo

Updated March 23, 2017

You don't have to be a mechanical wizard to connect a subwoofer to a car radio. Subwoofers provide bass to an audio system. The subwoofer's larger speaker demands a stronger signal than a standard factory stereo typically provides. For stereo systems not equipped with an amplifier, you will need to install an amp with your subwoofer or choose a powered subwoofer--a sub with a built-in amplifier.

Lift the bonnet of the vehicle. Disconnect the negative cable from the battery. The negative cable connects the battery to the frame of the vehicle. Loosen the cable's clamp with the 10mm wrench and move the cable away from the negative terminal.

Remove the bolt holding the positive cable to the positive battery lead. Place the ring terminal from the amplifier wiring kit onto the lead and replace the bolt with the wrench, securing the cable and ring terminal to the positive lead post.

Remove the fuse from the fuse holder on the ring terminal. The fuse holder is the coloured plastic casing midway down the cable of the ring terminal. Plug the power cable from the kit into the ring terminal. This will deliver power from the battery to the powered subwoofer.

Feed the power cable from the battery to the inside of the vehicle through the firewall. The firewall separates the engine compartment from the inside of the vehicle. Some vehicles will have an established opening for the cable. For vehicles without an opening, drill a hole in the firewall, behind the battery, and place a rubber grommet into the opening to protect the power cable from the sharp edges of the hole. Move to the interior of the vehicle.

Remove the vehicle's stereo. See your vehicle's repair manual for instructions on stereo removal.

Disconnect the stereo wiring from the rear panel of the stereo and connect it to a wiring harness adaptor. The adaptor will be colour-coded or have an accompanying manual detailing connection procedure.

Plug the wiring harness adaptor leads into the back panel of the stereo.

Plug the patch cables from the amplifier wiring kit into the corresponding leads of the wiring harness adaptor. The patch cables will provide the signal to the powered subwoofer and turn on the amplifier within the sub at the direction of the head unit.

Feed the patch cables through the rear of the stereo dock. The cables will emerge from the dashboard in the foot well of the passenger side of the vehicle, to be routed to the location of the subwoofer.

Replace the stereo into the dashboard of the vehicle. (See manuals for your vehicle's installation procedures.)

Route the patch cables from the stereo to the location of the sub. Hide the cables beneath the carpeting for a professional look. Lift the carpeting with a trim panel removal tool. Pry the carpeting from the floor at the side of the centre console and at the door openings to lay the cables from the front of the vehicle to the rear cargo area or boot. Consult the vehicle repair manual for any specific instructions on lifting and replacing the carpeting.

Route the power supply cable (from the foot well on the driver's side) to the subwoofer's location. Run the power cable and patch cables on opposite sides of the vehicle to avoid signal interference.

Plug the patch cables into the appropriate outlets on the subwoofer. Connect the power cable to the outlet labelled "power" on the sub.

Reconnect the negative battery cable to the negative battery terminal lead. Tighten the cable's clamp with the wrench. Replace the fuse into the fuse holder on the ring terminal and close the fuse holder compartment's lid.

Turn on the stereo and select the speaker arrangement mode. Enable the subwoofer and raise the volume of the source content (CD, radio, etc). Listen for the response from the subwoofer to ensure that it is working properly.

Disconnect the negative battery cable from the negative lead terminal with the wrench.

Place the subwoofer in the boot or rear cargo area of the vehicle.

Connect speaker wires to the amplifier's positive and negative outputs.

Route the speaker wire connected to the amp's negative output to the negative input of the subwoofer and connect the wiring. Route the speaker wire connected from the amplifier's positive output to the positive input of the sub and connect the wire.

Place the negative battery cable onto the negative battery lead post. Tighten the cable's clamp to the post with the wrench. Close the bonnet and test the subwoofer.

Things You'll Need

  • 10mm wrench
  • Amplifier wiring kit
  • Wiring harness adaptor
  • Trim panel removal tool
  • Speaker wire
  • Drill
  • Rubber grommet
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About the Author

Jule Pamplin has been a copywriter for more than seven years. As a financial sales consultant, Pamplin produced sales copy for two of the largest banks in the United States. He attended Carnegie-Mellon University, winning a meritorious scholarship for the Careers in Applied Science and Technology program, and later served in the 1st Tank Battalion of the U.S. Marine Corps.