The VRX932LAP is a powered, lightweight, compact 12" two-way line-array speaker system designed for use in arrays of up to five units. The VRX918SP is a powered, 18" direct radiating subwoofer designed specifically for use with the VRX932LAP Line Array speaker. This specially priced ground stack bundle combines four VRX932LAP speakers with four VRX918SP subs and speaker poles, which allow you to easily position your VRX932LAP's above the subs. Buy them together in this special bundle and save!