The L-Acoustics KS21 is a high-power, compact 21″ subwoofer engineered for professional sound reinforcement. It delivers exceptional low-frequency impact and clarity while maintaining a lightweight, road-ready design. It seamlessly extends the bandwidth of L-Acoustics A15 and A10 systems, making it ideal for concerts, events, installations, and touring applications where powerful, controlled bass is essential without sacrificing portability or rigging flexibility.

Key Features

• Powerful Performance with Exceptional Impact: A single high-excursion, direct-radiating 21″ neodymium cone driver in a bass-reflex enclosure provides deep, punchy low-end reinforcement. It achieves a maximum SPL of 138 dB and reaches down to a low-frequency limit of 29 Hz (with appropriate presets).
• L-Vents™ Technology: Laminar vented ports substantially reduce turbulence and port noise at high output levels while increasing low-frequency efficiency. This results in cleaner, sharper bass reproduction with minimal distortion.
• Flexible Directivity: Supports standard (omnidirectional) or cardioid configurations via dedicated presets and arraying. This allows precise control over rear bass rejection for cleaner stage sound or reduced noise in sensitive environments.
• Compact and Lightweight: Weighs just 49 kg (108 lb), striking an outstanding power-to-size ratio. The premium-grade Baltic beech and birch plywood cabinet uses bent wood and thickness optimization for maximum internal volume with minimal weight.
• Integrated Rigging and Handling: Features a flush-fitting two-point rigging system (compatible with A15), a pole mount (M20 x 150 insert), four ergonomic handles, eight corner stops, and two ground runners. This enables fast, secure stacking, flying, or ground deployment—even under stringent rigging conditions.
• Durability for Professional Use: IP55-rated for outdoor operations, with a coated steel grill protected by acoustically neutral 3D fabric, high-grade anti-corrosion steel rigging components, and a dark grey brown finish (Pantone 426 C).

Technical Specifications

• Description: High-power compact subwoofer (1 × 21″)
• Amplification: Powered by L-Acoustics LA4X, LA8, or LA12X amplified controllers
• Usable Bandwidth (-10 dB): 31 Hz – 100 Hz ([KS21_100] preset); operates from ~29–60 Hz with A15 or ~30–100 Hz with A10
• Maximum SPL: 138 dB (peak, half-space, pink noise with crest factor 4)
• Nominal Impedance: 8 Ω
• Connectors: 1 × 4-point speakON (IN) + 1 × 4-point speakON (LINK)
• Dimensions (W × H × D): Approx. 764 × 571 × 602 mm (30 × 22.5 × 23.7 in)
• Weight: 49 kg / 108 lb

The KS21 excels in delivering tight, articulate bass with high efficiency and minimal compromise. It pairs perfectly with L-Acoustics A Series loudspeakers for scalable systems in theaters, festivals, corporate events, or fixed installations. Its cardioid capability and L-Vents make it particularly effective in applications requiring controlled low-end directivity and pristine audio quality at high volumes.

For website use, you can shorten the intro to: “The L-Acoustics KS21 is a compact, high-power 21″ subwoofer that brings exceptional impact and clarity to any sound system. With L-Vents technology, cardioid options, and lightweight rigging, it delivers deep, controlled bass down to 29 Hz at up to 138 dB SPL—perfect for touring and installation.