The IL 218 Sub is a subwoofer designed to extend the lowrange frequency response of HK Audio IL 12.1, IL 12.2, IL 15.1 and IL 15.2 cabinets. It is loaded with two direct-radiating 18" cone loudspeakers housed in a bass reflex enclosure. The IL 218 Sub delivers powerful, low-ranging and dynamic bottom-end response at high volume levels. It is an excellent addition to fullrange and mid-/high-range systems for any sound reinforcement application requiring high sound pressure levels in the low frequency range. The IL 218 Sub must be operated in combination with an outboard active crossover or a hi-cut filter. The HK Audio Digital Field Controller (DFC) is recommended for larger and more complex application scenarios.