The REL Acoustics S/850 is the flagship of the Serie S range, positioned as the most advanced subwoofer in the line and the model whose design innovations filter down through the S/812, S/510, and S/310 stablemates. Serie S sits above the Serie T/x in REL's range hierarchy, offering upgraded components, faster filters, and more powerful amplification for listeners who require greater speed, clarity, and dynamic output in medium to large rooms.
Design
The S/850 cabinet is longer, lower, wider, and deeper than its predecessor, proportions that give it a naturally dynamic presence in a listening room. Subtle design details include 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 levelling, while thick internal aluminium slabs secure the handles for safe stacking when used in Line Arrays. The S/850 is finished in Piano Black Lacquer, applied in eight coats for a deep, durable gloss surface.
Driver and Passive Radiator
The S/850 uses a 12-inch (305mm) long-throw active driver built on a die-cast alloy chassis, with REL's CarbonAlloy cone construction. Pure carbon-fibre centre caps replace the solid aluminium mouldings of earlier models, reducing moving mass while stiffening the cone for explosive dynamics and the resolution of quiet musical passages. The down-firing passive radiator is a 12-inch (305mm) flat-piston design crafted from carbon, glass fibre, and closed-cell foam. It is 40% stiffer and significantly lighter than the previous generation, with over 60mm of travel in each direction to expand low-frequency authority and unlock the full scale of the amplifier.
Amplification
The 850-watt Linear Class D amplifier delivers continuous output with the ability to surge to 1,000 watts during demanding peaks. It is supported by a robust traditional power supply and features upgraded input filters using the same thin-film capacitors found in REL's flagship Reference series. All REL inputs use analogue signal processing rather than digital, preserving the natural character of the source signal.
Connectivity
The S/850 provides a full complement of inputs and outputs for both music and home cinema use. The High Level Neutrik Speakon input connects directly to a power amplifier's speaker terminals using the supplied 10-metre cable, preserving the character of the upstream amplifier. Two Low Level RCA inputs accommodate line-level sources, while a single LFE RCA and LFE XLR input serve home cinema processors. Matching High Level, Low Level, and LFE outputs allow the S/850 to be integrated into larger configurations. Wireless connectivity is available via the optional REL AirShip Direct system.
