Digital Designs DD Audio 9921 21" subwoofer


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21" 9900 Series 4" Voice Coil Subwoofer * Custom Order Only, Price Is Only A Guide.



The 9900s are the go to subwoofers for the demanding bassaholic with a profound interest in physics. Entertaining minds will revel in the endless system design possibilities deliverable with these precision low-frequency devices.

Originally coined The Beast, the 9900s first appeared on the market in the early 2000s. It took a brief hiatus, but now it’s back and more beastly than ever. The latest iteration was developed in response to the recent explosion in ultra-low-frequency music. These subwoofers were designed to provide long-term power handling, with accuracy, and high excursion capabilities. It’s been optimized for a 1500 – 2500 watt power band with the ability able to handle bursts of up to 10,000 watts. One look at the 9900 motor and you see why we call it the beast. It boasts 3 inches of magnet cross-section, over a 10″ OD, and weighs in at 70 pounds (motor only). The traditionally tight DD magnet gap drives a 4″ flat wound aluminum voice coil to a peak excursion in excess of 3 inches while keeping enough turns in the gap to maintain power and control.

The 9900 Series features our Evolution Subwoofer Package (ESP). ESP equipped drivers sport larger diameter suspensions and deeper frames than standard subs and exclusive surround and cone designs. ESP subs are truly built to maximize performance in their designated size class.

The 9900 Series comes standard with an oversized dry finish black composite dust cap, red logo, and treated pulp cone, but it can be optioned out with alternative composite dust caps, composite cones, powder coated frames, supercharging, and a multitude of logo options to give your sub a personalized look and/or added performance for a specific application.

Any DD Audio Product bearing the Marine Grade logo incorporates water resistant features enabling it to be used in applications where moderate exposure to moisture will not result in damage to the product.

Marine Grade products are not waterproof, and submersion or excessive moisture exposure may result in product failure. DD Audio Marine Grade products are not certified for saltwater environments.



  • Driver Size 21"
  • Watts RMS 1500 - 2500
  • Peak Power 10000
  • VCD 4
  • Impedance D1 / D2         
  • Piston Dia – in 18 1/4
  • Fs – Hz 26.24
  • Qms 5.265
  • Qes 0.517
  • Qts 0.471
  • Vas – liters 161.9
  • dBSPL 89.42
  • Xmech – mm 92
  • Xmax – mm 22
  • Frame OD – in 21 5/16
  • Frame OD w/Gasket – in -
  • Mounting Diameter – in 19 1/4
  • Mounting Depth – in 11 5/16
  • Motor Diameter – in 10 5/16
  • Motor Depth – in 4 9/16
  • Woofer Displacement - cu ft 0.55
  • Sealed Enclosure - cu ft N/a
  • Ported Enclosure - cu ft 6.0 - 8.0
  • Shipping Weight – lbs 92

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