Alpine SWR-1242D Type-R 12" subwoofer with dual 4-ohm voice coils at Crutchfield
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Insane Bass From Two 12" Alpine Type R (SWR12D4) Subwoofers!! - YouTube
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Universal Car Stereo Slotted S Port Single 10" Alpine Bundle Type R R-W10D4 Sub Box Enclosure with Harmony HA-A800.1 Amplifier & 4GA Amp Kit - Walmart.com