How to connect one passive subwoofer to an amplifier

Written by tracy underwood
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How to connect one passive subwoofer to an amplifier
You don't necessarily need a huge array of subwoofers; one may be enough. (Inside sound system image by Dmitry Sosenushkin from

Adding a subwoofer is one of the best ways to improve the sound and presence of a car sound system. Contrary to popular belief, it is not necessary to have a huge speaker box and two or more subwoofers to upgrade your system. Because low frequencies are non-directional, using a single subwoofer will not impact the stereo separation, and you can place it under the driver's seat or in some other unobtrusive location. Active or self-powered subwoofers are available as an add-on component to an existing car audio system, but these tend to be underpowered. Using an unpowered or passive subwoofer in conjunction with a separate amplifier to power it is a big step up, while remaining a reasonably simple upgrade.

Skill level:

Things you need

  • Line-level subwoofer output from your head unit or crossover
  • Amplifier to power the subwoofer
  • Subwoofer
  • RCA cable(s)
  • Speaker wires

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  1. 1

    Find the line-level subwoofer output on your head unit or crossover. If there is only one connection, it is a monaural output; if two, it is stereo. Connect an RCA cable to the output. If your sub output is stereo, connect two RCA cables; one to each output.

    How to connect one passive subwoofer to an amplifier
    Line-level subwoofer output (subwoofer image by MATTHIEU FABISIAK from
  2. 2

    Choose the amplifier you want to use. If you have stereo subwoofer outputs, you may easily use either a bridged or stereo-only amplifier. If there is only a monaural sub connection, you have no choice but to use a bridgeable amplifier.

    Connect the free end of your RCA cable or cables to the inputs of the amplifier. A bridgeable amp will have a switch to place it in the mono mode. If you will be using it as a mono amp, consult the owner's manual supplied with the amp for directions to properly place it in mono mode.

  3. 3

    Choose your woofer. If you will be using your amplifier in stereo mode, you will need a woofer with dual voice coils. This provides two sets of connections in one speaker, so that it is electrically two speakers. If your amp is bridged, a standard woofer with one voice coil will suffice.

  4. 4

    Connect the speaker. Make sure of the polarity; the red or + terminal on the amp should be wired to the red or + terminal on the speaker. Likewise, connect the black or - terminal on the amp to the corresponding black or - terminal on the speaker.

  5. 5

    Connect the power and relay circuits as indicated in the instructions that came with the amp. Check all your wiring, install the fuse in the power supply line and enjoy a whole new dimension in your music.

    How to connect one passive subwoofer to an amplifier
    Speaker connection (speaker connector image by jovica antoski from

Tips and warnings

  • Always disconnect the negative battery cable before working on the power supply wiring to your amplifier.

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