d&b audiotechnik 21S 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 be 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.

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
with D80
134 dB
135 dB
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

Additional information

Weight 119 lbs
Dimensions 21 × 23 × 44 in