Polk Audio TL250 Compact, High Performance Home Theater System (5-pack, Black) Compact, 5-piece High Performance Home Theater System Time Lens Technology-The acoustic centers of the tweeter and mid-bass driver are located in the same plane for superior imaging PowerPort, a patented Polk technology, extends the low frequency mid-bass driver response as it decreases air turbulence, 3/4" Silk Dome Tweeters for crisp, clear imaging and smooth response that's never tiring. 3 1/4" Composite Injection Molded Cones With Dynamic Balance Driver Technology Time Lens Technology-The acoustic centers of the tweeter and mid-bass driver are located in the same plane for superior imaging PowerPort a patented Polk technology, extends the low frequency mid-bass driver response as it decreases air turbulence, 3/4" Silk Dome Tweeters for crisp, clear imaging and smooth response that's never tiring. 3 1/4" Composite Injection Molded Cones With Dynamic Balance Driver Technology Combination Keyhole Slot & 1/4" x 20 Threaded Insert fits all aftermarket ceiling and wall brackets for ultimate flexibility. Eliminates "port noise" and bass output losses up to 3 dB.