To facilitate fit, multi-application adaptor rings are included with the C1-650x allowing easy, drop-in installation in vehicles equipped with oversized 6.5-inch and 6.75-inch speaker openings. Without the ring, the speaker will fit into many "6-inch" speaker locations as well. C1 woofer drivers benefit from proprietary FEA modeling and JL Audio's expertise in low-frequency driver design. This knowledge is used to create speakers that can play loudly, while maintaining a smooth, dynamic, low distortion sound. At the core of the C1-650x is a proprietary, stamped, steel 6.50-inch (165 mm) frame and a DMA-optimized motor system. A mineral-filled, injection-molded polypropylene cone is suspended with a rubber surround on the front, and a carefully engineered flat Conex spider at the top of the voice coil, to precisely control the voice coil's motion. Tinsel leads are carefully routed and attached to the spider to prevent fatigue and buzzing. These are the same kinds of features and materials normally found on much more expensive loudspeakers. Equipped with a true, edge-driven, aluminum dome tweeter, C1 speakers stand further apart from others in its category with superior high-frequency clarity and definition. The tweeter's design has inherently excellent off-axis response and high-frequency extension.