REL Acoustics S/850 B-stock

S/850 stands as the benchmark of the Serie S line, with its design innovations shaping and elevating its three stablemates. Every improvement is sweeping and comprehensive, ensuring the entire Serie S family benefits from the advancements pioneered in the S/850.

The results are spectacular: it delivers incredible attack and output beyond even the former Carbon Special at the very limits of performance, yet with the precision, quietness, and clarity that produce true dynamic range. Lightning-fast transients, deep effortless bass, and tonal richness combine to deliver nuance that elevates both music and theater.

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.

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.

 

Specifications:

Type

Front-firing active driver, down-firing passive

Active Driver Size & Material

12 in. (305mm) long-throw, CarbonAlloy™ cone structure, die cast alloy chassis

Passive Radiator Size & Material

12 in. (305mm), Carbon/Carbon flat cone structure, steel chassis

Low Frequency Extension

-6 dB at 19Hz

Input Connectors

High Level Neutrik Speakon, Low Level (2) RCA, (1) LFE RCA, (1) LFE XLR

Output Connectors

High Level Neutrik Speakon, (1) Low Level RCA, (1) LFE RCA or (1) LFE XLR

Power Output

850 watts (RMS)

Amplifier Type

Linear Class D

Wireless Capability

REL AirShip Direct (sold separately)

Dual Parametric Filter

N/A

Finish

Piano Black Lacquer, Gloss White Lacquer 8 coats

Protection System

Fully Electronic Set Safe

Yes

D.C. Fault

Yes

Output Short

Yes

Mains Input Voltage

220-240 volts, 110-120 volts for certain markets

Fuses

8 Amp semi delay 220 volts operation, 15 Amp semi delay 120 volts operation

Supplied Accessories

Mains Lead

Yes

Neutrik Speakon

Yes (10 Meters Nominal)

Interconnect

–

User Manual

Yes

DIMS

W x H x D
19.25 x 16.125 x 21.25 in.
(488 x 410 x 540 mm)

Net Weight

93.5 lbs. (42.5 kg)