Dual Voice Coil (DVC) woofers are simply speakers with two voice coils wrapped around the same voice coil former. This allows the speaker to be connected in 3 different ways. With the individual coils wired in series, the resulting impedance will be 2 times the impedance of each individual coil. Wiring the coils in parallel will make the impedance 1/2 the impedance of each individual coil. This means that a speaker with dual 4 ohm coils can be wired to 2 ohms or 8 ohms.