Polk Audio RM6752 Center Channel Speaker (Single, Black) Single center speaker designed to accommodate the rear surround channel in Polk's RM6750 speaker system Dual 3.25-inch polymer composite cone midrange drivers and 0.75-inch high-performance silk dome tweeter PowerPort bass vent technology improves the lower midrange response for better sat/sub blending Integrated baffle and grille design disperses the sound beautifully for clear, well-balanced, room-wise audio Magnetically shielded against video interference