Bose FreeSpace 3 Series I Acoustimass Black50 230 Hz, PTC, 70 100 V, Max SPL 96 dB, 5 , 5. 25", 191 x 342 x 356 mm, 7. 9 kg Designed to provide surface mount bass augmentation for new and existing background music systems. Features one 5. 25" (133 mm) woofer that delivers deep bass down to 40 Hz without audible distortion. Low frequency loudspeaker featuring one 5. 25" (133mm) woofer that delivers deep, non localized bass down to 40 Hz without audible distortion. For surface mount applications