Twin 6-5/16" (16cm) Super Woofers and Super Twin Ducts A pair of extra-large 6-5/16" (16cm) Super Woofers gives you powerful, deep bass sound in combination with a number of JVC technologies. Units are mounted back-to-back to cancel out vibrations, while the Super Twin Ducts deliver crisp, extended bass sound. A weight ring coupled to the woofer helps extend response down to under 100Hz. A 6-layer voice coil shifts down the lowest resonance frequency and increases driving power. The woofer units also feature foamed rubber surround to achieve both high linearity and low distortion.