Polk Audio RTiA1 5.25" High Performance Bookshelf Loudspeaker, 50Hz-27kHz, Pair, Cherry Acoustic Resonance Control (ARC Port) technology for more natural midrange reproduction 1-inch Silk/Polymer Dome Tweeter delivers smooth response and better detail /Magnetic shielding for safe placement near video sources Mylar bypass capacitors in the crossovers extend high frequency response and improve detail and transparency Neodymium magnet,low-viscosity ferro-fluid cooling, and a heat sink on the back of the magnet, create better power handling and reliability Gold-plated 5-way binding post inputs (with wide holes for large-gauge bare wire connections)