Why the REL S/850 Stands Out
REL Acoustics is a British specialist that does not build ordinary subwoofers. It builds sub-bass systems designed to integrate so completely with your main speakers that you stop thinking about the subwoofer entirely and simply hear a bigger, deeper, more effortless version of your existing system. The REL S/850 sits within REL's S line, the range built around carbon-fibre driver technology, greater output, and the kind of speed that keeps low frequencies tuneful rather than merely loud.
The S/850 is a serious performer built for listeners who want real authority in the bottom octaves without giving up the nuance that makes music and film convincing. It is a natural choice when a smaller REL no longer fully energizes the room, or when your main speakers and amplifier deserve a partner that can keep pace.
Design and Technology
Driver and Radiator Configuration
The S/850 uses a 12 inch forward-firing long-throw active driver paired with a 12 inch down-firing passive radiator. This arrangement is central to its character. The active driver delivers the immediacy and speed REL is known for, while the down-firing passive radiator reinforces the lowest frequencies and loads the floor, adding weight and extension without the port noise you might expect from a lesser design. The result is bass that arrives fast, hits with genuine slam, and decays cleanly.
Class A/B Amplification
Driving the S/850 is a Class A/B amplifier chosen for its musicality and control. REL voices its subwoofers to start and stop with the main speakers, and the amplifier is a big part of why the S/850 feels agile rather than ponderous. It has the headroom to stay composed during demanding passages, whether that is a full orchestra swelling or a large-scale film sequence.
The High Level Connection
REL's signature is the High Level connection, made with a Neutrik Speakon cable taken directly from your power amplifier's speaker terminals. This means the S/850 receives the exact same amplified signal, with the same tonal character and timing, as your main speakers. For two-channel music this is the heart of REL's seamless integration. The subwoofer inherits the personality of your amplifier and speakers rather than imposing a sound of its own.
The S/850 also provides a low-level RCA input for line-level connections and a dedicated .1/LFE input for home theater, so it slots comfortably into a surround system with bass management as well. You can even run both connections at once, using High Level for music and the LFE input for movies.
Setup Controls and Isolation
Dialing the S/850 into a room is straightforward thanks to continuously variable crossover, gain, phase, and level controls. These let you match the subwoofer precisely to your speakers and the acoustics of your space rather than settling for fixed steps. Isolation feet are included to decouple the cabinet from the floor, tightening the bass and reducing unwanted transmission into the structure. The high-gloss black and high-gloss white finishes are furniture grade, so the S/850 looks at home in a living space, not just a dedicated room.
Performance Character
The S/850 is fast, deep, and controlled. It brings out the foundation of a recording, the body of a cello, the pressure of a kick drum, the room ambience around a live performance, without ever calling attention to itself. In a home theater it delivers the kind of physical impact that makes large scenes feel real, yet it never turns muddy or one-note. This dual nature, equally at home with delicate music and demanding cinema, is exactly what the S line was engineered to achieve.
Where It Sits in the REL Range
Within the S line, the S/850 sits a step above the REL S/550. Both share the S line design philosophy and the same commitment to speed and musical integration. The S/850 moves up the ladder with its larger driver and passive radiator configuration and greater output, making it the stronger match for larger rooms or systems that call for deeper, more effortless low-end authority. If your room is more moderate in size, the S/550 may be all you need. If you want more output and more room-filling foundation, the S/850 is the natural step up.
Below the S line, REL's Classic and T/x series serve listeners focused on entry audiophile musicality, while above it the Reference tier such as Carbon Special offers still greater refinement and output. The S/850 occupies the sweet spot of high performance that many two-channel and home-theater enthusiasts find is exactly the right balance.
Ideal System and Speaker Matching
Because the S/850 integrates through the High Level connection, it is designed to reinforce whatever full-range speakers and amplifier you already love. A few pairings from our shelves illustrate the range of systems it complements.
The Klipsch Heresy IV Heritage floorstanders are lively and dynamic but roll off in the lowest octaves, and the S/850 fills that foundation beautifully while preserving their immediacy. The MoFi SourcePoint 10 Master Edition bookshelf speakers are superb midrange and imaging performers that benefit enormously from a REL underpinning their bottom end, giving you full-range scale from a compact monitor.
On the amplification side, a refined integrated such as the Yamaha A-S1200 makes an excellent High Level partner for two-channel listening. For a system that spans music and cinema, the Yamaha RX-A8A AV receiver can feed the S/850 through its .1/LFE input for movies while still supporting the High Level connection for music. The Devialet Phantom Ultimate 108 dB is another intriguing partner for those who want a modern, powerful main speaker complemented by REL's tuneful foundation.
Completing the Hookup: Cables and Wireless
The S/850 arrives ready for a wired High Level or LFE connection. For a dedicated LFE run in a home-theater setup, the REL Commander is a purpose-built LFE cable that keeps the signal path clean. If you prefer a third-party option, AudioQuest offers a family of subwoofer cables including the AudioQuest Boxer, Greyhound, Irish Red, and the higher-tier Husky in RCA or Husky in XLR, each differentiated by build and materials rather than by any claim of superiority over one another. Choose the one that suits your run length and system.
If routing a cable across the room is impractical, the S/850 is compatible with REL's wireless systems. The REL HT-Air MKII transmits the signal wirelessly to the subwoofer, removing the need for a long physical run, and the REL Arrow is another option to consider. Remember that a wireless transmitter makes no sound on its own; it serves a specific compatible subwoofer, so confirm the match before you buy. The S/850 is also compatible with REL AirShip II and HT-Air MKII, both sold separately.
Going Further with a Line Array
One of REL's most rewarding upgrades is adding a second S/850. Two RELs stacked in a line array deliver greater output and a noticeably larger, more enveloping soundstage. Many listeners find that a pair of subwoofers does more for realism than any single larger box could, and the S/850 scales gracefully into a stereo pair.
Frequently Asked Questions
Why choose the REL S/850?
REL Acoustics is a British specialist that does not build ordinary subwoofers. It builds sub-bass systems designed to integrate so completely with your main speakers that you stop thinking about the subwoofer entirely and simply hear a bigger, deeper, more effortless version of your existing system.
Where does the REL S/850 sit in the range?
Within the S line, the S/850 sits a step above the REL S/550 . Both share the S line design philosophy and the same commitment to speed and musical integration. The S/850 moves up the ladder with its larger driver and passive radiator configuration and greater output, making it the stronger match for larger rooms or systems that call for deeper, more effortless low-end authority. If your room is more moderate in size, the S/550 may be all you need. Below the S line, REL's Classic and T/x series serve listeners focused on entry audiophile musicality, while above it the Reference tier such as Carbon Special offers still greater refinement and output. The S/850 occupies the sweet spot of high performance that many two-channel and home-theater enthusiasts find is exactly the right balance.
What cables and connections does the REL S/850 need?
The S/850 arrives ready for a wired High Level or LFE connection. For a dedicated LFE run in a home-theater setup, the REL Commander is a purpose-built LFE cable that keeps the signal path clean.
Let Us Help You Match It
All Elite Audio is an authorized REL Acoustics dealer with a showroom in Timonium, Maryland. Demo units rotate and not every model is always set up, so we invite you to contact AEA to arrange a listen or to help match the S/850 to your speakers and room. We are happy to talk through connection options, wireless modules, and whether the S/850 or another point in the REL range best suits your system.