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d&b audiotechnik 21S-SUB


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Product Overview

High Performance Subwoofer

The 21S-SUB is a high performance subwoofer for use with the xS-Series and xA-Series loudspeakers and is intended for a wide range of permanently installed applications. The cabinet houses a single long excursion 21" driver in a bass-reflex design. The large, specially shaped reflex port enables the 21S-SUB to achieve high Sound Pressure Levels from a cabinet with a small footprint.

When operated in INFRA mode, the 21S-SUB can be used to complement other d&b subwoofers by extending the frequency response of the system down to 33Hz. The 21S-SUB can ground stacked or flown in either orientation. It can be flown individually or in a cluster of two cabinets.

The enclosure is constructed from marine plywood with an impact resistant black paint finish. The front of the loudspeaker cabinet is protected by a rigid metal grill backed by an acoustically transparent foam. The top, bottom and rear panels each incorporate a pair of M10 threaded inserts for attaching d&b rigging hardware. The Weather Resistant option enables the operation of loudspeakers in changing ambient conditions, and features a fixed cable. The 21S-SUB can also be supplied in any RAL colour. This Special Colour option can be provided for rigging accessories.


The d&b audiotechnik loudspeaker range is designed exclusively for operation with d&b amplifiers.

These provide power as well as comprehensive control and protection functions tailored to achieve the performance, reliability and longevity associated with the d&b System approach. The d&b 30D amplifier is recommended to drive the 21S-SUB. The d&b D20 and D80 amplifiers can also be used with the appropriate loudspeaker configuration selected.




System data 

  • Frequency response (–5 dB standard): 35 - 105 Hz
  • Frequency response (–5 dB INFRA mode): 33 - 85 Hz
  • Max. sound pressure (1m, free field) [1]
    with D20/30D: 134dB
    with D80: 134dB
  • Cabinets per amplifier channel: 1


Loudspeaker data

  • Configuration: Installation specific high performance subwoofer with compact footprint
  • Nominal impedance: 4 Ω
  • Power handling capacity (RMS/peak 10 ms): 650/2600 W
  • Components: 21" driver with neodymium magnet
  • Connections:
    1 x NL4
    1 x screw terminal block


Dimensions, weight

  • Dimensions (H x W x D): 1100 x 580 x 526 mm (43.3 x 22.8 x 20.7")
  • Weight: 54 kg (119 lb)


[1] SPL max peak test signal: pink noise with crest factor 4

* Application information is presented for guidance only. d&b reserves the right to make any necessary changes to the products and the published specifications. As part of the ongoing development program d&b tries to maintain the highest degree of product compatibility.

Product Downloads

  • 21S-SUB Data Sheet PDF 0.2 MB
  • 21S-SUB User Manual v1.1 PDF 0.9 MB
  • 21S-SUB xS-Series Brochure PDF 5.0 MB


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*Prices are in AUD, include GST and are subject to change. Please call National Audio for pricing and availability on the 21S-SUB.