9921b: 1500w to 2500w - 21 Inch Power Tuned Subwoofer - DD Audio
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MT21A Built-in DSP single 21" Self-powered Subwoofer with Compact Cabinet Box - Buy 21" subwoofer, single 21 inch subwoofer, self powered subwoofer Product on Sanway Professional Audio Equipment Co., Ltd.
Dayton Audio HTS545HE-4 Kraken 21" High Excursion Subwoofer with 5" Voice Coil 4 Ohm
Yorkville Sound SA221S Synergy Array Series Dual 21" SA221S B&H
21 inch Eminence Tour Grade Replacement Speaker – Eminence Speaker, LLC
Eminence NSW6021-6 21" Professional Neodymium Tour Grade Subwoofer Driver
Amazon.com: Sound Town 21” 1000W Cast Aluminum Frame Woofer (Low Frequency Driver), Replacement Woofer for PA/DJ Subwoofer Cabinets (STLF-21500A) : Musical Instruments
RCF LF21X451, Woofer 21", 2000 Watt RMS / 8 Ohm | MUSIC STORE professional
Amazon.com: DS18 PRO-BX21N.1 Car Subwoofer Audio Speaker - 21" in Neodymium Magnet, 6" Voice Coil, 1 Ohm Impedance, 3000W Rms Power, 6000W Max Power - Reinforced Paper Cone for Outstanding Performance : Electronics
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VS21 21" Powered Sub - BASSBOSS Powered Loudspeakers