The HDX3 series heavy-duty subwoofer is well suited for use as a competition subwoofer with a beefy, monstrous, made in the USA dual voice coil! Find it in 12 inch, 15 inch and 18 inch sizes! The HDX3 can handle 1500 Watts RMS power and 4500 Watts Peak power for burps. HDX3’s motor features a thick top plate, high motor force, and a tight gap for high-efficiency speaker design. A taller 4-spoke, cast aluminum frame makes room for a larger diameter spider for lower tuning and greater accuracy. The larger diameter spider’s new roll profile allows for low F’s without sacrificing power handling or control. The HDX3’s taller and wider surround allows for even more precise excursion and new pulp-blend cones are stronger than previous fiberglass-laminate designs- And they’re lighter too! We are ditching the stitching on the 1500 Watt Power Band.Other improvements over the HDC series subwoofers include the presence of a thicker, more robust aluminum former, as well as black anodizing. Double slit venting and a higher temperature resin are included for increased cooling abilities, enhanced performance, and a longer subwoofer life. Model HDX312 HDX315 HDX318 RMS Power 1500 W 1500 W 1500 W Peak Power 4500 W 4500 W 4500 W Magnet Weight 300 oz 300 oz 300 oz Coil Diameter 3" 3" 3" Coil Length 50 mm 50 mm 50 mm Usable Throw 68 mm 68 mm 68 mm Woofer Size 12" 15" 18" F(s) 26.92 Hz 26 Hz 27.59 Hz Impedance D1 / D2 D1 / D2 D1 / D2 Z(max) 70.16 Ohm 63.8 Ohm 55.47 Ohm Q(ms) 4.95 4.847 5.777 Q(es) 0.3409 0.3665 0.4724 Q(ts) 0.3189 0.3408 0.4367 V(as) 28.59 Liters 78.08 Liters 168.6 Liters L(e) 2.553 2.711 2.563 n(0) 15.60% 33.96% 71.46% M(ms) 440.9 grams 472.8 grams 410.9 grams C(ms) 0.079 0.082 0.081 Sensitivity 1W/1m 84.03 dB 87.41 dB 90.64 dB BL 31.45 30.49 25.14 Xmax 36mm 36mm 36mm Sd 0.051 m2 0.082 m2 .121 m2 Displacement 0.16³ 0.18³ 0.23³ Mounting Depth 8 7/8" 9 1/2" 10.5" Circle Cutout 11 1/2" 13 7/8" 16 9/16" Ported Enclosure (Cu Ft): 1.75-2.75 FT³ 3-6 FT³ 5-7 FT³