Alpine SWR-1240D Subwoofers

I have a pair of these.

They are 12" subs.

Here is a nice shot of the magnet.

Here is a picture of them from the factory.

Features: Woofer Bass Engine Ready Bumped Backplate Custom Cast Aluminum Frame Designed and Engineered in the USA Dual Progressive Oversized Nomex? Spiders Dual Stacked Magnets Dual Voice Coil Design Extra Length Extended Pole Flared Pole Vent Heat Transfer Plate Heavy Duty 8ga. Push Terminals High Excursion 1" Santoprene Surround High Strength Brass Voice Coil Bobbin Kevlar Reinforced PulpCone Oversized Parabolic Dustcap Specs: General-Subwoofers Diaphragm Material : Kevlar Reinforced Pulp Magnetic Weight : 64oz. Mounting Depth (top mount) : 175mm (6-7/8O) Mounting Diameter (top mount) : 275mm (10-13/16O) Recommended Box Types : Sealed/Vented/Bandpass Recommended Sealed Box Volume : 0.75 ? 1.0 cu. ft. Spider Material : Nomex Voice Coil Diameter : 50mm Power Handling Power Handling Capacity (Peak) : 1000W Power Handling Capacity (RMS) : 300W Thiel Small Parameters Coil Height (Hvc) : 36.6mm Cone Area (Sd) : 467.59 sq. cm D.C.Coil Resistance (Re) : 3.6 ohm + 3.6 ohm Electrical Q (Qes) : 0.43 Equivalent Suspension Stiffness (Vas) : 66 liters(2.33cu.ft.) Free Air Resonance (Fs) : 27Hz Frequency Response : 27Hz - 1kHz Gap Height (Hag) : 10mm Impedance (Nominal) : Dual 4 ohm Inductance (Le) : 3.95mH at 1kHz (1.35mH at 20kHz) Linear Excursion (X linear) : 12.9mm Maximum Excursion (X peak) : 25.8mm Mechanical Excursion (Peak-to-Peak) : 55mm Mechanical Q (Qms) : 9.98 Sensitivity : 87 dB/W/M Total Loudspeaker Q (Qts) : 0.41