How to Bridge Two 12-Inch Subs


Any car audio enthusiast will tell you that a good sound system needs serious bass, and while a system with a single subwoofer can sound good, a system with two 12-inch subs can sound great. But what if you already have a single subwoofer in your car running off a single-channel amplifier? If you know what you're doing, it's possible to use your existing amplifier to run two subs at the same time. All you need is an additional subwoofer and some speaker wire.

Things You'll Need

  • Two 12-inch subwoofers
  • Power amplifier
  • Speaker wire
  • Wire strippers
  • Connect the first subwoofer to the amplifier using speaker wire, if it is not already connected. One end of the speaker wire should connect to the spring clips or binding posts on the amplifier. The other end of the speaker wire should slide into the spring clips on the back of the subwoofer enclosure. Hold the spring clip down to open the connection, insert the wire into the hole, then release the clip to secure the connection. Ensure that all connections are secure before proceeding.

  • Arrange both subwoofers in their correct positions in your car's trunk, then cut a second piece of speaker wire to the length necessary to connect the two. Use wire strippers to remove the insulation 1/2 inch from each end of the wire. Insert one end of the speaker wire into the first subwoofer (along with the wire that's already connected) following the procedure outlines in step 1. Be sure that both wires are securely connected to the subwoofer.

  • Connect the free end of the speaker wire to the second subwoofer, using the procedure outlined in step 1. Ensure that the speaker wire is securely connected to the subwoofer. You have now completed the wiring process.

  • Test your system by turning on you car stereo and setting the volume to the minimum level. Slowly increase the volume, listening carefully for any static or other abnormal sound. Both subwoofers should be producing an equal volume level, and strong, clear bass. If you hear anything abnormal, turn off your sound system and check all connections.

Tips & Warnings

  • Ensure that both subwoofers have the same impedance rating. Impedance is measure in ohms.
  • The combined load of both subwoofers should not exceed the amplifier's lowest usable impedance. To calculate the combined load, divide the single-speaker rating by the number of speakers connected. For example, two 8-ohm speakers connected to one amplifier would create a 4-ohm combined load. Check your amplifier's user manual for its lowest usable impedance.
  • Be sure to connect the color-coded terminals on the amplifier to the same-color terminals on the subwoofers. Red and black are the colors used most often.

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  • Photo Credit Matthew Peyton/Getty Images Entertainment/Getty Images
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