SA-8 V.3 D4 - Sundown Audio 8" 500W RMS Dual 4-Ohm SA Series Subwoofer SA-8 V.3 D4 - Sundown Audio 8" 500W RMS Dual 4-Ohm SA Series Subwoofer Specifications: DC Resistance (Re): 6.0  | Resonance Frequency (Fs): 40.0 Hz | Equivalent Volume (Vas): 7.17 L | Electrical Q Factor (Qes): 0.392 | Mechanical Q Factor (Qms): 4.310 | Total Q Factor (Qts): 0.360 | Force Factor (BL): 22.06 NA | Moving Mass (incl. Air Load) (Mms): 126.6 g | Suspension Compliance (Cms): 125 m/N | Sensitivity: 82.71 dB 1w / 1m Box Recommendations: Sealed Enclosure Suggestion: Not Recommended | Ported Enclosure Suggestion: 0.5 - 0.75 cu. ft. @ 35 Hz | Displacement: 0.08 cu. ft. | Depth: 6.625 in |Outside Diameter: 8.375 in | Cutout: 7.375 in