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.
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.
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.
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.
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.
