S 21

Touring high performance compact 21″ subwoofer

TransducersLF : 1 x 21″
SPL peak / 1m (measured)139 dB
Weight58.8kg / 129.63lbs
RiggingPole mount
Share this product


S 21 is a compact, high-performance passive touring subwoofer, designed to complement our FR-X, ARES 8 and ARES 12 series in sound reinforcement applications scaling to full stadium shows.

S 21 houses a long excursion 21″ neodymium driver and combines front diffusion, bass reflex, and transmission line design for maximum efficiency and outstanding SPL.

Rental companies favor S 21 as an alternative to industry-standard 2×18” subs, saving half the truck space and around 40% of the weight. The subwoofer can be deployed standalone, stacked or flown, making it a versatile, high-earning hire stock staple.

S 21 is built with pride in Belgium and coated in tough, weather-resistant polyurea to safeguard your investment. The cabinet front is protected by a rigid metal grill, backed by acoustically transparent foam.

S 21 can be quickly deployed in any configuration, including cardioid and end-fire, when used with AUDIOFOCUS A Series amplifiers. Armonia presets are also available for Powersoft amplifiers.


  • Powerful bass-reflex T-line design
  • Lightweight and portable
  • Pole mount socket
  • Passive

Technical specifications

DescriptionHigh-power subwoofer
Transducers LF: 1 x 21″
Frequency range (-6dB)28Hz – 100 Hz
SPL peak (1)139 dB
ProcessingDedicated AUDIOFOCUS and Armonia/Powersoft omni and cardioid presets
RiggingPole socket
Connectors2 × 4-point speakON
Nominal Impedance4ohm
Watt AES/peak1700/6800W
Dimensions (H x W x D)590 x 750 x 655 mm
23.22 x 29.52 x 25.78 inches
Weight58.8kg / 129.63lbs
FinishHighly resistant polyurea coating

CabinetHigh grade birch plywood

(1) Peak level measured at 1 m under free field conditions using pink noise with crest factor 5

Gll files for Ease and Easefocus
S 21

Gll • 1.65 Mo • 06/01/2022

Gll files for Ease and Easefocus
S 21 Stack

PDF • 149 Kb • 19/04/2024

A Series Output Chart
S 21

PDF • 2.76 Mo • 17/10/2022

Powersoft Presets
S 21

Zip • 17 Ko • 20/12/2022

SCiO Presets
S 21

Zip • 43 Ko • 09/01/2023