Subwoofers add rumble and excitement to any car audio system. Without this low bass power, musical energy and dynamics are not what they could be. Smaller speakers in the door, dash and deck typically lack the ability to reproduce the lowest two musical octaves, so a subwoofer is essential rather than optional if accuracy is important to you. Making the right choices with the amplifier in terms of power, number of channels and impedance capability influences your choice of subwoofer and determines your overall enjoyment.
Getting a Handle on Impedance
Impedance issues may be the most important consideration when wiring a subwoofer. Impedance or "load" at the amplifier influences power output and overall system stability. Too high an impedance causes bass reproduction to suffer. With too low an impedance, amplifiers shut down or fail. Matching the amplifier's impedance abilities as described in product documentation with that listed from the subwoofer's maker is critical for proper performance. Staying within the normal impedance range of 2 to 4 ohms is ideal, blending maximum power with a sound level of amplifier stability.
Voice Coil Quantity
Single voice coil subwoofers offer little wiring mystery, with the positive and negative terminals on the amp and sub wired in sync. Dual voice coil subwoofers add a few variables; wiring them one way or another either increases or decreases the load at the amplifier. DVC subs have two sets of voice coils. Jumping the terminals one way on a dual 4-ohm subwoofer creates a 2-ohm load, while jumping them the opposite way offers an 8-ohm response. Depending on the amplifier, this may make a huge difference in perceived bass response. When wiring a single DVC subwoofer, follow the supplied documentations carefully to determine which scheme is best for you particular subwoofer.
Series and Parallel Wiring
Going hand-in-hand with voice coil quantity is series and parallel wiring. Series wiring consists of jumping the positive and negative terminals between two or more subwoofers in a daisy chain manner, increasing the impedance at the amp. Using this example, a pair of 2-ohm subwoofers wired in series creates a 4-ohm load at the amplifier. Wiring the same pair in parallel yields a 1-ohm load, which is potentially an unstable situation for many amplifiers. Parallel wiring consists of wiring positive leads to positive terminals and negative leads to negative terminals as opposed to wiring positive to negative as occurs in series wiring.
Amplifier Channel Selection
Mono amplifiers have appropriate names, possessing only a single amplifier channel. However, mono amplifiers are typically Class-D; they offer cooler-running operation, high efficiency and low impedance stability. It is not uncommon to see mono amplifiers used in 1-ohm applications, something almost never recommended with stereo amplifiers. Stereo amps make up for this however with increased wiring flexibility, including the ability to drive one or more subwoofers per channel or operating in bridged mode. Stereo amps with this option use the left positive and right negative channels, creating a single more powerful channel from a lesser pair.
- Matthew Peyton/Getty Images Entertainment/Getty Images