S 21i

Installation high performance compact 21″ subwoofer

TransducersLF : 1 x 21″
SPL peak / 1m (measured)139 dB
Weight58,8kg / 129.63lbs
RiggingM8 threaded insert
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S 21i is a compact, high-performance passive subwoofer for fixed installations, designed to complement our FR-X, ARES 8 and ARES 12 series in theatres, houses of worship, live music venues, stadiums, and other sound reinforcement applications.

S 21i houses a long excursion 21″ neodymium driver and combines front diffusion, bass reflex and transmission line design for maximum efficiency and outstanding SPL. Cardio and end fire on every version.

Deployed standalone, stacked, or flown, S 21i adapts to mirror the needs of the venue and offers huge space and weight savings compared to industry-standard 2×18” subs.

S 21i 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.

We recommend AUDIOFOCUS or Powersoft amplifiers for use with S 21i.


  • Powerful bass-reflex T-line design
  • Optimized for installation
  • Lightweight and portable
  • Threaded inserts
  • Passive

Technical specifications

DescriptionHigh-power subwoofer
Transducers LF: 1 x 21″
Frequency range (-6dB)28Hz-100 Hz
SPL peak (1)139 dB
ProcessingDedicated AUDIOFOCUS SCiO and Armonia/Powersoft omni and cardio presets
RiggingM8 threated insert
Connectors2 × 4-point speakON
Nominal Impedance8ohm
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

S 21 Stack

Gll • 1.78 Mo • 06/01/2022