Eminence IMPERO 18C 18" High Power Driver Speaker 4 Ohm 1200W The Eminence Impero 18C 18" high power pro audio speaker is optimized for use in vented enclosures. Its 1,200 watt continuous power rating is a result of Eminence's extensive experience designing and manufacturing loudspeaker drivers for serious professional use. This 18" cast frame transducer features a 4" diameter copper voice coil that is wound on a fiberglass former. A large magnet, extended and vented pole piece, bumped back plate, and 1/2" thick x 7-1/2" diameter top plate ensure substantial motor strength, resulting in tremendous bass output. The Impero 18C's performance is Ideal For 4 ohm full-range 3-way boxes, bass guitar boxes, and compact to medium-sized subwoofer speaker systems. Recommended enclosure volume: Vented: 113.2 ~ 277.5 liters / 4 ~ 9.8 cu. ft.