How to Bridge a Four-Channel Amp

Bridging a four channel amplifier dramatically increases output.

Four-channel car audio amplifiers offer a little more versatility to mobile stereo systems over their mono and two-channel cousins. Although many choose a four-channel amp to drive their midrange and tweeter speakers in their car stereo, better units are bridgeable. This process multiplies the output of the four channels, converting them into two high-output channels. This is then used to drive a pair of subwoofers or demanding component speakers.

Things You'll Need

• Screwdrivers (Philips, Allen, Torx)
• Speaker wire
• Wire snips
• Wire strippers

Instructions

1. Examine the speaker wire output terminals on the four-channel amp. Locate the markings under or above the terminals marked "Bridge." Of the eight total screws, four will be marked for bridged operation.

2. Loosen the four screws used for bridged operation. Cut two lengths of speaker wire sufficient to reach from the amplifier's installed location to the speakers or subwoofers you wish to power.

3. Slide the two sets of wires into the loosened speaker terminals. One set of wires corresponds to the left channel bridged output, with the other set corresponding to the right channel's output.

4. Tighten the screws back down to secure the wires at the amp. Connect the wires to the speakers, ensuring that the wire connected to the positive output terminal matches with the positive terminal on each speaker. Repeat for the negative leads. The four channel amp is now running in bridged two-channel mode.

References

• Crutchfield: Four Channel Amp Bridged Diagram
• Basic Car Audio and Electronics: Bridgeable Amplifiers