Filter Filters 18" $500 and above Remove All Filters Condition New (5) Brand Harmony Audio (5) Harmony HA-ML1X18D2 18" Dual 2-OHM Subwoofer Vented Enclosure Box Subpackage $549.95 2x Harmony HA-ML181 Monolith 18" Competition SPL Sub 3500W Dual 1 Ohm Subwoofer $724.99 4x Harmony HA-ML181 Monolith 18" Competition SPL Sub 3500W Dual 1 Ohm Subwoofer $1420.99 4x Harmony HA-ML182 Monolith 18" Competition SPL Sub 3500W Dual 2 Ohm Subwoofer $1420.99 2x Harmony HA-ML182 Monolith 18" Competition SPL Sub 3500W Dual 2 Ohm Subwoofer $724.99