How to Wire Two Dual Voice Coil Subwoofers to a Two Channel Amplifier

by David Lipscomb Google

    Whether used in home or mobile audio applications, dual voice subwoofers provide additional wiring flexibility when compared to single voice coil options. This flexibility comes with the added responsibility of ensuring the electrical impedance is correct, allowing maximum power output while maintaining amplifier stability. Combining the right amplifier with the right pair of DVC subwoofers will make the difference between pavement pounding sound or an unreliable sonic disappointment.

    Impedance

    Impedance measures the amount of effort required by an amplifier to get a speaker moving. The lower the impedance, the more power provided by the amplifier. Too low of a load however, and the amplifier enters thermal protection, mutes or suffers damage. The subwoofer's impedance rating is located on the speaker's carton, in its documentation and on a label affixed to the bottom of the magnet. Most car audio amplifiers are intended to operate reliably between 2 and 8 Ohms, although you will encounter specialty outliers rated for 1-Ohm operation. If your system is built for maximum boom as opposed to sound quality, low impedance operation can be an important factor as it pertains to extracting the most power from the amp.

    Series and Parallel Wiring

    Series wiring sums the total impedance of both DVC subwoofers. For example, wiring two DVC 4-Ohm subwoofers in series presents an 8-Ohm load to the amplifier, well within safe operating range but with lower output than you may want. Conversely, wiring in parallel halves each impedance. Using the same two 4-Ohm subwoofers in parallel, the load presented to the amplifier is now 2 Ohms. However, the danger lies in accidentally wiring a pair of 2-Ohm DVC subwoofers in parallel, which presents a probably unstable 1-Ohm load to the amplifier. Always attempt to stay within the safe range of 2 to 8 Ohms, with 2 to 4 Ohms preferable to combine output with reliability.

    Power Calculations

    Recall that lowered impedance raises power output. For example, an amplifier that outputs 200 watts for two subwoofers at 4 Ohms would in theory double to 400 watts at 2 Ohms. At 8 Ohms, the opposite occurs. Not all amplifiers double output in a linear fashion, so check your product documentation for specific ratings per impedance. When examining power ratings, look for the RMS or average for both the subwoofers and amplifier. Matching these numbers as closely as possible helps ensure reliable and predictable performance.

    On Bridging

    Bridging a stereo amplifier takes two channels and combines them to create a more powerful single channel. Many amplifiers outputting 100 watts per channel in stereo could for example produce as much as 400 watts mono. Remember however that bridging an amplifier places more strain on amplifier outputs. This is why it is not desirable to bridge a stereo amp with a 2-Ohm subwoofer, for example, since the amplifier "sees" a 1-Ohm impedance. However, it is possible to wire a pair of dual voice coil 4-Ohm speakers bridged to a stereo amplifier and still present a 4-Ohm load. This is done by connecting the positive terminals for both subwoofers to each other, as well as the negatives. A single wire jumps the inner positive and negative coils on each woofer, increasing the impedance of each to 8 Ohms. The positive wire for the first subwoofer connects to the left positive terminal on the amp, with the negative of the first sub to the right negative channel output.

    About the Author

    David Lipscomb is a professional writer and public relations practitioner. Lipscomb brings more than a decade of experience in the consumer electronics and advertising industries. Lipscomb holds a degree in public relations from Webster University.

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