Klipsch R-15M Bookshelf Speaker (Pair) Get power and versatility in a small package, the Klipsch R-15M bookshelf speakers pack a mean punch. These speakers perform beautifully as a left,center,right, or surround. Dual 5.25" copper-spun high-output IMG woofers. Brushed black polymer veneer cabinet Klipsch Reference Bookshelf speakers feature a rear-firing port that is perfectly match to the cabinet and drivers. Features bass reflex via rear firing port enclosure type. Sensitivity 94 db at 2.83 volt per 1 minute