Installing car audio subwoofers in your vehicle will provide better low-end frequency response from your stereo. Aftermarket car audio manufacturers produce many different subwoofer types and sizes, designed to accommodate your vehicle's size and your listening preferences. Subwoofers require a separate external amplifier for power. It is important to properly match the total nominal power handling of the subwoofers used in your system with the RMS power output figure of the amplifier. When wiring a pair of 10-inch subwoofers with single 4-Ohm voice coils, you must consider the Ohm load capability of the amplifier as well.
Read the documentation supplied with the subwoofer and amplifier.
Determine if the amplifier is a mono-block subwoofer amplifier or two-channel amplifier. When wiring the subwoofers to a mono-block, the device must support a 2-Ohm speaker load. Two-channel amplifiers must support a 2-Ohm load in bridged mode, which means the two side's output is "bridged" together.
Cut two pairs of speaker wire long enough to reach from the amplifier's speaker terminals to the subwoofer box terminals. Strip off 1/8 inch of insulation from the ends of each speaker wire, using a pair of wire strippers. Twist the wire strands together to prevent fraying.
Determine the type of wire terminals used on the amplifier. If the amplifier uses the "bar-and-screw" type terminals, crimp spade terminals to one end of each speaker wire pair, using the crimping tool portion of the wire strippers. If the amplifier features setscrew type wire terminals, do not connect spade terminals to the one end of each speaker wire pair; you will insert the speaker wire into the terminals directly.
Connect the stripped end of one speaker wire pair to the corresponding terminals on the subwoofer box for the left subwoofer. Connect the stripped ends of the remaining speaker wire pair to the right-side subwoofer terminals. The striped line on certain speaker wire brands will denote the red "Positive" lead, while the solid color wire in the pair must connect to the black "Negative" speaker box terminal.
Loosen the negative "-" and positive "+" speaker terminals on the amplifier, using a Phillips head screwdriver, flat head screwdriver or Allen wrench, depending upon the terminal type.
Insert the "Positive" speaker wire leads from each subwoofer into the amplifier's "+" speaker terminal. Secure both speaker wire leads to the amplifier by tightening the terminal screw.
Connect the "Negative" speaker wire leads to the "-" speaker terminal found on the amplifier, and tighten the terminal screw.
Check the connections for tightness and wire frays that may cause shorts in the system.
Examine the documentation supplied with your amplifier, and determine which terminals you must use for a "Bridged" subwoofer connection. Certain amplifiers may provide indications near the speaker terminals. Typically, bridging the amplifier consists of connecting the positive speaker wires to the "Right Channel" positive terminal on the amp, while connecting the negative leads to the "Left Channel" negative amplifier terminal (or vice-versa).
Loosen the two speaker terminals used for bridging with a Phillips head screwdriver, flat head screwdriver or Allen wrench.
Connect the "Positive" speaker leads for each subwoofer to the appropriate positive "Bridged" terminal on the amplifier. Tighten the terminal screw to secure the wiring to the amplifier.
Connect the "Negative" speaker leads for each subwoofer to the negative "Bridged" amplifier terminal. Tighten the terminal screw to secure the wiring to the amplifier.
Check the speaker terminals for tightness and the wiring for any frays.
