Definitive Technology ProMonitor 800 Bookshelf Speaker (Single, Black) Single ProMonitor bookshelf speaker Equipped with one 4.5-inch cast basket bass/midrange drivers coupled to one 4.5-inch pressure-driven planar low-frequency radiators Frequency response: 57Hz - 30kHz Equipped with one 1-inch pure aluminum dome tweeter The high quality finish is available in gloss black or gloss white