Foam

I have a Rockford Fosgate – Punch 12" Dual-Voice-Coil 4-Ohm Subwoofer
Model: P3D412 | SKU: 8266342
Handles up to 1000W peak power (500W RMS)
Die-cast aluminum basket and trim ring
KEVLAR®-reinforced cone (KEVLAR is a registered trademark of DuPont)
High-temp voice coil with spun lace Nomex insulating reinforcement collar
Extended excursion range tall profile surround
Venturi-effect center pole dispersion venting/cooling system
Spring-loaded connection terminal
High-density compressed half-roll sealed poly foam surround
Double-stacked 102 oz. magnet design
Sensitivity: 84dB
Impedance: 4 ohms

WITH THIS AMP:
Kenwood – 1000W Class D Bridgeable Mono Amplifier with Variable Crossover – Black/Blue
Model: KAC-8104D | SKU: 8696351
1000W peak output @ 4 ohms, bridged
500W peak output @ 2 ohms
300W peak output @ 4 ohms
500W RMS (continuous) x 1 @ 2 ohms
300W RMS (continuous) x 1 @ 2 ohms
Adjustable 50-200Hz low-pass crossover
40Hz bass boost circuit (+18 dB, variable)
Cooling fan for improved performance
Blue illumination

Like this – http://i81.photobucket.com/albums/j230/sparky3489/SINGLE-PARALLEL.jpg

More info here http://skrbox1.spaces.live.com