Alpine SWR-8D4 8" Subwoofer (4Ω + 4Ω) General Features: 8" Dual 4-Ohm Type-R Series Car Subwoofer Power Handling: Peak: 1000 watts RMS: 150-350 watts Impedance: Dual 4 ohms Reinforced Parabolic Cone Structure with Poly-Mica Dust Cap & Pulp-Kevlar Cone Durable HAMR Santoprene surround Nomex Progressive Conex spider Compound Radius Curve pole geometry Oversized 1.6", High-Temperature, 4-Layer Dual Voice Coil 52 oz. Double Strontium magnet motor structure Frequency response: 30-200 Hz Resonance Frequency (Fs): 40Hz Excursion: 12mm Top-mount depth: 4-1/2" Sensitivity: 83.5dB