Effortless Power, Tuned for Musical Authority

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S/850 is engineered for listeners who want uncompromising performance with a refined, musical touch. Drawing on innovations from our Reference line, it pairs an 850-watt Linear Class D amplifier with advanced CarbonAlloy™ drivers to deliver explosive dynamics, clarity, and effortless scale. Equally at home in high-end music systems or immersive theaters, S/850 brings control and confidence to medium-to-large rooms.

850-watt Linear Class D Amplifier for fast, controlled power delivery
12" CarbonAlloy™ Active Driver with 12" long-stroke Passive Radiator for depth and speed
Optimized for music and theater systems in medium-to-large rooms
Designed for stereo pairs and line-array configurations
Optional premium wood grille available. Crafted from natural materials, each grille features unique grain and color variations
Designed to be Perfect
The S/850 cabinet is longer, lower, wider, and deeper—proportions that give it a naturally dynamic presence. Subtle design details refine its look and feel: clean creases that catch the light, warm silver-gold badges with a titanium-like finish, and stainless-steel handles recessed into graceful ellipses. Beneath each front rail, precision-milled billet cylinders provide exact leveling, while thick internal aluminum slabs secure the handles for safe stacking in Line Arrays. Designed to complement modern interiors, the S/850 also offers an optional Premium Wood Grille, adding warmth and individuality.

Driven to Perfection
The S/850 is the result of relentless refinement. This progress comes not only from exploring newer, finer materials, but also from the thousands of hours of critical listening our team undertakes each year—experience that transforms raw engineering into musical and theatrical performance of the highest order. With every detail carefully considered, the S/850 delivers a level of power, nuance, and scale that redefines what’s possible in its class.

S/850 drivers now feature lightweight pure carbon-fiber center caps, replacing the solid aluminum moldings of earlier models. These caps reduce moving mass while stiffening the cone, resulting in explosive dynamics and the ability to resolve the quietest passages with delicacy and nuance. Feather-light yet rigid, they extend performance at both extremes—a hallmark of REL design.

Passive Radiator

Supporting this advanced active driver is a newly engineered down-firing passive radiator. Purpose-built to handle the extreme throw distances produced by the S/850’s more powerful amplifier and driver system. Its flat, primary-piston surface—crafted from carbon, glass fibre, and light, stiff closed-cell foam, represents an evolution of prior designs but is now 40% stiffer and significantly lighter. With over 2.4" (60mm) of travel in each direction, it expands dynamics and low-frequency authority, unlocking the full scale and impact of the S/850.

Monoblock Slam, Class D Efficiency

The S/850’s amplifier delivers the slam of massive Class A/B monoblocks while harnessing the efficiency of a modern Class D output stage. Supported by a robust traditional power supply, it produces 850 watts of continuous output and can surge to 1,000 watts during demanding peaks, ensuring ample headroom for both music and theater. Upgraded input filters, equipped with the same thin-film capacitors used in our flagship designs, introduce a new level of transparency and refinement previously unheard of in this class. Together, these advancements create dramatic improvements in clarity, sound staging, and sheer authority—an amplifier that blends brute force with finesse to anchor the performance of the entire Serie S line.

Analog Filtered to Perfection:

We choose analog because it is the only way to achieve truly natural sound. All REL input filters are 100% analog—among the fastest ever offered in a subwoofer. At the core is our renowned High Level Input, which connects directly to the speaker outputs of your main amplifier. This doesn’t draw power; instead, it carries the full sonic signature of your system, allowing REL to blend seamlessly with your speakers—a quality reviewers have praised for decades.

For systems where High Level isn’t possible, our low-level input uses the same analog filter circuit, available via both RCA and XLR connections, to deliver the speed, naturalness, and integration REL is known for. And in theater or dual-use systems, REL uniquely allows High Level and .1/LFE to run together—so music benefits from natural integration, while movies deliver the full impact intended by the mix.

What's in the box

Serie S/850 Subwoofer

6' AC Power Cord

32' Neutrik Speakon cable

Line Array Mounting Hardware

Cloth Grille

User Manual and Warranty Information

*The Premium Wood Grille is NOT included in your subwoofer purchase but is available for purchase.

REL

REL S/850 White