Polk Audio TL1 Speaker Center Channel (Each, Black) Time Lens Technology-The acoustic centers of the tweeter and mid-bass driver are located in the same plane for superior imaging. Aperiodic-tuned rear port enables better blending with a subwoofer. Total Frequency Response: 95 Hz to 22 Hz, Nominal Impedance: 8 ohms 2.5 inch Long-throw drivers with Dynamic Balance Driver Technology. sensitivity (1 watt at 1 meter): 89 dB 1/2 inch Silk dome tweeters for crisp, clear imaging and smooth response that's never tiring Combination keyhole slot & 1/4" x 20 threaded Insert fits all aftermarket ceiling and wall brackets for ultimate flexibility The Time lens technology enables the acoustic centers of the tweeter and mid-bass driver are located in the same plane for superior imaging.