Polk Audio CSI A4 Center Channel Speaker (Single, Cherry) A single center channel speaker timbre-matched to fit any Polk Audio home theater or multi-channel music system Two 5.25-inch dynamic balanced drives with polymer composite cones One 1-inch silk composite dome tweeter Features a neodynium magnet, low viscosity ferro-fluid cooling, and a heat sink on the back of the magnet All MDF construction and extensive asymmetric cabinet bracing ensure resonance-free enclosures