JBL GTO1214D 12-Inch Die Cast Dual Voice Coil Subwoofer Polypropylene woofer cone is both strong and lightweight Proprietary die-cast frame allows optimum alignment of the motor structure to ensure low distortion even at high output levels and excursion limits. Dual 4-ohm voice coils allows for optimum system matching and performance Vented pole pieces adds additional cooling to the motor structure which increases power handling. Rubber surround provides an optimal blend of elasticity and internal damping for the proper amount of control and stability at excursion limits.