Features Include || Bifilar, Low Inductance Voice Coil || Selectable 1, 2+2, or 4Ω || 21” Nominal Diameter || 5000 W Program Power || Spaced Dual Spiders || 24mm Xvar || Applications || Subwoofer | Pro Audio || Box Type: Vented, Sealed, Scoop Loading, Horn Loading || SPECIFICATION || Nominal Basket Diameter : 21", 533 mm || Nominal Impedance* : 1, 2, or 4 Ω || Program Power : 5000 W || Watts (AES) : 2500 W || Resonance : 30.67 Hz || Usable Frequency Range : 25 Hz - 0.6 kHz || Sensitivity* : 95.0 dB || Magnet Weight : 45 oz. || Gap Height : 0.75", 19 mm || Voice Coil Diameter : 6", 152 mm || Mirror Image Twin Spiders : 13 mm Spacing || THIELE & SMALL PARAMETERS (1) || Resonant Frequency (fs) : 30.67 Hz || DC Resistance (Re) : 2,9 Ω || Coil Inductance (Le) : 1.2m H || Mechanical Q (Qms) : 10.38 || Electromagnetic Q (Qes) : 0.33 || Total Q (Qts) : 0.32 || Compliance Equivalent Volume (Vas) : 224.58 liters / 7.93 cu.ft. || THIELE & SMALL PARAMETERS (2) || Peak Diaphragm Displacement Volume (Vd) : 3448.2 cc || Mechanical Compliance of Suspension (Cms) : 0.05 mm/N || BL Product (BL) : 30.5 T-M || Diaphragm Mass Inc. Airload (MMs) : 551 grams || Efficiency Bandwidth Product (EBP) : 92.68 || Maximum Linear Excursion (Xmax) : 21 mm || Surface Area of Cone (Sd) : 1642 cm2 || Maximum Mechanical Limit (Xlim) : 40.4 mm || MOUNTING INFORMATION || Recommended Enclosure Volume : || Sealed : 122.61–181.79 liters/4.33–6.42 cu.ft. || Vented : 155.74-481.39 liters / 5.50-17.00 cu.ft. || Driver Volume Displaced : 0.379 cu.ft. / 10.72 liters || Overall Diameter : 21.65", 549.9 mm || Baffle Hole Diameter : 19.83", 503.7 mm || Front Sealing Gasket : YES || Rear Sealing Gasket : N/A || Mounting Holes Diameter : 0.34", 8.6mm || Mounting Holes B.C.D. : 20.67", 525mm || Depth : 10.39", 263.9 mm || Net Weight : 48.1 lbs, 21.82 kg || Shipping Weight : 51.6 lbs, 23.41 kgs || MATERIALS OF CONSTRUCTION : || Coil Construction : I/O Copper voice coil || Coil Former : Fiberglass former || Magnet Composition : Neodymium magnet || Core Details : Vented motor || Basket Materials : Die-cast aluminum basket || Cone Composition : Wet pressed, X5 cone pulp || Cone Edge Composition : Advanced Polycotton surround || Dust Cap Composition : Wet pressed, X5 dust cap pulp ||