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.

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.

S 21i 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
  • Optimized for installation
  • Lightweight and portable
  • Threaded inserts
  • Passive

Technical specifications

DescriptionHigh-power subwoofer
Transducers LF: 1 x 21″
Frequency range (-6dB)28Hz-100Hz
SPL peak (1)139 dB
ProcessingDedicated AUDIOFOCUS SCiO and Armonia/Powersoft omni and cardioid presets
RiggingM8 threated insert
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

Gll • 1.65 Mo • 06/01/2022

Gll files for Ease
and Easefocus Stack

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