Active 18" Subwoofers The SP-18 and SP-1818 active 18? subwoofers are designed for mobile entertainers and permanent installations in Discotheques, Churches, Corporate AV and Live Stage Applications. With more than 1200 watts of rock-solid power, a frequency response down to 30 Hz and a peak SPL of over 135 dB, these subwoofers deliver earth-shattering, chest-thumping bass with the easiest of system connectibility. The 18? subwoofer(s) feature cast-aluminium frames, 4? high-temp. polyamide voice coils and 200 ounce vented magnet structures. The patent-pending DIGITAL amplifier (pictured right) used is over 90% efficiency, produces minimal heat, draws less than 12 amps of electrical current and is loaded with intelligent features. The raw power, high-efficiency and extremely low THD of the SP-Series subwoofers are complimented by their rock solid reliability.