HD-690CF - CDT Audio 6" x 9" Carbon Fiber Subwoofer Cast Mid-Woofer 1 pr 6X9 carbon fiber subwoofer The HD-690CF 6X9 subwoofer is designed and built for the unique demands of the car audio environment. Built to deliver the truest, in-car sound possible. Voice coil: 2.0 Mounting depth: 3.5