Polk Audio RTI A9 Floorstanding Speaker (Single, Black) Single real wood floorstanding speaker with all MDF construction and resonance-free enclosures Equipped with dual 5.25-inch polymer composite cone drivers and three 7-inch polymer composite subwoofers Features Power Port technology to reduce "chuffing" or "port noise" Equipped with one 1-inch silk/polymer composite dome tweeter Features a neodynium magnet, low viscosity ferro-fluid cooling, and a heat sink on the back of the magnet