X-15 V.2 D2 - Sundown Audio 15" Dual 2-Ohm X V.2 Series Subwoofer X-15 V.2 D2 - Sundown Audio 15" Dual 2-Ohm X V.2 Series Subwoofer Specifications: DC Resistance (Re): 3.80  | Resonance Frequency (Fs): 29.6 Hz | Equivalent Volume (Vas): 58.9 L | Electrical Q Factor (Qes): 0.40 | Mechanical Q Factor (Qms): 4.65 | Total Q Factor (Qts): 0.37 | Voice Coil Inductance (Le): 2.53 mH | Force Factor (BL): 25.6 NA | Moving Mass (incl. Air Load) (Mms): 366.8 g | Suspension Compliance (Cms): 0.08 mm/N | Sensitivity: 87.7 dB 1w / 1m Box Recommendations: Sealed Enclosure Suggestion: Not Recommended | Ported Enclosure Suggestion: 4.25 cu. ft. | Displacement: 0.22 cu. ft. | Depth: 10.85 in | Outside Diameter: 15.51 in | Cutout: 13.83 in | Recommended Tuning: 32 Hz | Recommended Port Area: 68 sq. in.