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How to Install Subwoofers in a Car

by Contributor

Most car manufacturers do not include subwoofers with the factory stereo system. The process of installing them can be complicated, so avoid hassle by purchasing a prefabricated enclosure box equipped with subwoofers. Make sure you gain proper knowledge as well as tools, so your installation is a success, as an improper installation can cause damage to your vehicle.

Step 1

Reconfigure the speaker hookups on your four-channel amplifier so that the front and rear speakers already in the system are using the 2 front channels of the amplifier. The front channels of the amplifier should have a high-pass crossover to work these speakers.

Step 2

Bridge the rear channels of the amplifier into mono so that the amplifier will supply twice the power. The instructions that came with the amplifier will show you how to do this.

Step 3

Wire the two subwoofers into the amplifier using 12-gauge speaker wire (unless otherwise specified by the instrutions). The rear channel of the amplifier should have a low-pass crossover.

Step 4

Test to see what the best crossover point is for the subwoofers.

It is recommended to use metal L-brackets to brace the enclosure. Secure the box to the floor, a wall or the rear deck. Be sure to place silicone around the bracket so that air will not leak from the box. Note: If your spare tire is located in your trunk (which is common on most vehicles), you may want to skip this step.


  • Play around with the positioning of the subwoofer box in the trunk to get the sound you want. You may find it best to point the box so that the subwoofers are aimed toward the rear or toward the interior of the vehicle. When pointing toward the rear, the sound wave has a longer distance to travel, and you get more bass as a result. Directing your box towards the seat will add a vibrating more powerful feeling to the interior but can also cause damage to the subwoofer if placed to close to the seat.
  • To test for the best crossover point for the subwoofers, set the low-pass crossover of the amplifier at 100 Hz and play something on your system. Watch the movement of the subwoofers. The lower the crossover-point frequency, the less movement on the subwoofers. Watch to see whether the subwoofers are moving too much and listen to the music to determine whether there is distortion. Most systems run at 85 or 80 Hz.
  • Make sure you seal the box in it's correct position and use the proper depth screw
  • To deal with vibrations, you can spray your trunk with a polyurethane based product, although this can be a bit costly. A cheap alternative is spray foam insulation that one would use around windows and cracks on a house. This can be picked up at your local home center.


  • Before you place the L-brackets, check to see what is on the other side of the surface you will be screwing into. You don't want to cut a gas line or wire.

Items you will need

  • Four-Channel Amplifier
  • Subwoofer box with subs
  • Manufacturer Recommended Cabling
  • Phillips Screwdrivers
  • Car Stereo Wires
  • Spray Glues
  • Rollers
  • Subwoofer Enclosures
  • Brackets
  • Variable-speed Drills
  • Blow Dryers Or Heat Gun
  • Car Stereo Subwoofers

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