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Monolith 13 THX Ultra has some SERIOUS excursion!!! - YouTube
Amazon.com: Monolith THX Ultra Certified 2000 Watt Powered Subwoofer - 13-Inch, Massive Output, Low Distortion, for Studio and Home Theater Systems, Black Ash Finish : Electronics
Monoprice Shakes Things Up With Two New Massive THX Subwoofers [Updated] - ecoustics.com