Filter Filters 18" $500 and above Remove All Filters Condition New (2) Brand Harmony Audio (2) 2x Harmony HA-ML181 Monolith 18" Competition SPL Sub 3500W Dual 1 Ohm Subwoofer $724.99 4x Harmony HA-ML182 Monolith 18" Competition SPL Sub 3500W Dual 2 Ohm Subwoofer $1420.99