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

Atrium Series Speakers exceed baseline industrial and military specifications for environmental endurance (ASTM D5894-UV Salt Fog, Mil Standard 810 Immersion, Mil-Std 883 Method 1009.8 for salt and corrosion.) Anodized Aluminum Tweeter Domes with Rubber Surrounds are absolutely immune to the elements, provide the smooth, broad high-end range you need for larger outdoor spaces Newly designed tweeter phase cap smoothes the frequency response from 12KHz up to 20kHz, the last audible octave.