Filter Filters 18" Remove All Filters Price $100-$500 (3) $500 and above (5) Condition New (8) Brand Harmony Audio (8) Voice Coils Dual (2) Sensitivity 88.4dB (2) Harmony Audio HA-ML182 Monolith 18" Competition Sub 3500W Dual 2 Ohm Subwoofer $379.95 (2) Harmony Audio HA-ML181 Monolith 18" Competition Sub 3500W Dual 1 Ohm Subwoofer $379.95 (1) 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 Harmony Audio HA-BV1X18E Universal Single 18" Empty Vented Port Sub Box... $209.95