d&b audiotechnik 21S-SUB Subwoofer


The d&b audiotechnik 21S-SUB is a space-saving, flyable subwoofer for fixed installation with a 21″ neodymium driver in an impact-resistant, bass-reflex cabinet with rubber feet for stacking protection, and side-panel bracket threads for flown installation.


About this item



d&b audiotechnik 21S-SUB Subwoofer

The 21S-SUB houses a 21″ neodymium driver housed in a space-conscious cabinet, built for fixed installation in a variety of applications. Designed for use with d&b audiotechnik xS-Series and xA-Series loudspeakers, the 21S-SUB is a high-performance, 2,600W (peak) design with a maximum SPL of 135dB. The 21S-SUB cabinet houses a long-excursion, 21″ neodymium driver in a bass-reflex design. The large, specially shaped reflex port enables the 21S-SUB to achieve high sound pressure levels (SPL) with minimal power compression and breathing effects. 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 be ground-stacked or flown in either orientation. It can be flown individually or in a cluster of two cabinets.

D&b audiotechnik 21S-SUB—At a Glance:

  • Installation-specific, high-performance compact subwoofer
  • 21″ neodymium driver
  • Bass-reflex design with a uniquely shaped port for high SPL
  • Omni-directional dispersion
  • 135dB maximum SPL
  • Use in standalone, stacked, or as a base for a mixed ground stack
  • Rubber feet prevent movement and protect the bottom panel

D&b audiotechnik 21S-SUB—Parsing the Details

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 color. This Special Color option can be provided for rigging accessories. The loudspeaker cabinets and most accessories are also available with the Special Color (SC) option that can be executed in all RAL* colors, while the Weather Resistant (WR) option provides an IP55* rating, and enables the operation of loudspeakers in changing ambient conditions.

*RAL is a color-matching system that defines standard colors for varnish, powder coating, and plastics. It’s the most popular Central European color standard used today.

**The IP Code or International Protection Rating, sometimes also interpreted as Ingress Protection Rating. IP55: Protected from limited dust ingress and protected from low-pressure water jets from any direction.  

21S-SUB rigging components  

The top, bottom, and side panels of the cabinet are each equipped with a pair of M10 threaded inserts to connect to different rigging accessories such as:

  • Z5555 Horizontal bracket 21S-SUB
  • Z5556 Bracket extension 21S-SUB
  • Z5557 Flying bracket 21S-SUB

For use as a base, the 21S-SUB is equipped with four rubber feet to prevent cabinet movement and protect the bottom panel against scratching. The cabinet is Ball-Impact Resistant according to DIN 18032-3. 

Compatible amplifiers

The d&b amplifiers are designed specifically to power d&b loudspeakers, forming the heart of the d&b System. They incorporate digital signal processing for comprehensive loudspeaker management, switchable filter functions, remote capabilities, and user-definable controls to fulfill the exact needs of each application.

d&b LoadMatch  

Starting with the D80 amplifier platform, the LoadMatch function enables the amplifier to electrically compensate for the properties of the loudspeaker cable used without the need for an additional sense wire. For applicable loudspeakers, LoadMatch is therefore independent of the connector type used.

The d&b 30D amplifier is recommended to drive the 21S-SUB. The d&b D20 and D80 can also be used.

21S-SUB applications:

  • Sports venues
  • Multipurpose halls
  • Concert halls
  • Nightclubs and bars
  • Theater and opera
  • Educational facilities
For assistance ordering or configuring a d&b audiotechnik system with 21S-SUB subwoofers and xS- or xA-series loudspeakers, call or chat online with your Parsons Audio Professional today. 


System data

  • Frequency response (-5 dB standard): 35Hz – 105Hz
  • Frequency response (-5 dB INFRA mode): 33Hz – 85Hz

Max. sound pressure*

  • D20/30D amplifier: 134dB
  • D80 amplifier: 135dB
  • Cabinets per amplifier channel: 1

Loudspeaker data

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

Dimensions / Weight (H x W x D) (Approx.)

  • Height: 43-5/16″
  • Width: 22-13/16″
  • Depth: 20-11/16″
  • Weight: 119 lb. / 54 kg

* 1 m, free field, SPL max peak test signal: pink noise with crest factor 4

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