The Klipsch RB-51 is a part of the larger Klipsch Synergy line and is similarily built to the same specifications as the Reference series floorstanding versions. Klipsch has released the Synergy line as a smaller, bookshelf replication of the Reference speakers. The RB-51 uses a 5.35-inch Cerametallic woofer with an inverted copper dust cap and a rear-firing port for clear, accurate bass frequencies. The high-frequency driver is a 1-inch Exclusive Tractrix titanium tweeter with a neodymium motor structure to handle the other sonic spectrum. Klipsch has increased baffle ribbing around the horn mouth to improve all sonic acoustics and features a 2,000 Hz high frequency crossover.