REL S Series Subwoofers: S/550 vs S/850 Buying Guide

Why the REL S Series

The REL S series sits above the entry T/x and Classic ranges and below the Reference tier, and it is where REL's performance ambitions really open up. These are subwoofers engineered as sub-bass systems, which means they are designed to integrate with your full range speakers rather than simply add rumble. If you love music first but also want convincing scale for films, the S series is the range where REL brings greater output, faster transient speed, and refined driver technology into one cabinet.

Specifications compared

All Elite Audio is an authorized REL dealer, and we work with these models daily. Below we explain the shared design language of the range, then compare the two S series subwoofers we carry so you can match one to your speakers and room.

The Shared REL Design in the S Series

Every S series subwoofer is built around a few core REL principles.

High Level Connection

The hallmark of REL is the High Level connection, a Neutrik Speakon cable that draws signal directly from your power amplifier's speaker terminals. This lets the subwoofer receive the same amplified signal and tonal character as your main speakers, which is the key to seamless music integration. Both the REL S/550 and the REL S/850 offer this connection, and it is a large part of why these subs disappear into a two channel system.

Full Input Flexibility

In addition to High Level, each model provides a low level RCA input and a dedicated .1/LFE input. That means you can run High Level for music and take an LFE feed from a processor for home theater, giving you the best of both worlds in a single subwoofer.

Closed Cabinet with Passive Radiator

Both models use a forward-firing active driver paired with a down-firing passive radiator in a sealed enclosure. This design goal is tight, fast, tuneful bass with meaningful low frequency extension, rather than the looser output of a large ported box.

Precise Setup Controls and Wireless Options

You get a continuously variable crossover, level control, and phase adjustment on each model, so integration with your speakers and room is straightforward. Both are also compatible with REL's wireless systems for situations where a wired run is impractical. Remember that a wireless transmitter makes no sound on its own and serves a specific compatible subwoofer, so confirm the match before ordering.

The Models Compared

REL S/550

The REL S/550 pairs a 10 inch forward-firing long-throw alloy cone with a 12 inch down-firing passive radiator, driven by a 500 watt Class D amplifier. It reaches down to approximately 21 Hz in room, which is genuinely deep, and it does so with the agility the S series is known for. It is compatible with the REL AirShip II wireless system as an option, and it comes in high gloss black or high gloss white. At roughly 17.7 by 14.75 by 18.0 inches and about 46 pounds, it is a substantial but manageable cabinet.

Who it suits: The S/550 is an outstanding match for high quality bookshelf and medium floorstanding speakers in small to medium rooms. If your priority is musical nuance with the ability to hold its own in movies, and your space is not cavernous, this is a beautifully balanced choice.

REL S/850

The REL S/850 steps up the driver complement with a 12 inch forward-firing long-throw active driver and a 12 inch down-firing passive radiator, and it uses a Class A/B amplifier. The larger active driver and the character of that amplifier are aimed at greater output and effortless authority, moving more air with ease for larger speakers and larger rooms. It shares the same High Level, low level, and .1/LFE inputs, and it is compatible with both the REL AirShip II and HT-Air MKII wireless options. Isolation feet are included, and it is offered in high gloss black or high gloss white.

Who it suits: The S/850 is designed for larger floorstanding speakers and bigger rooms where you want the subwoofer to keep pace without strain. It suits the listener who wants more headroom and scale while retaining REL's musical integration.

Grouping the Two by Tier

Both subwoofers live within the same S series REL range, so neither is inherently better than the other. They are voiced to the same family goal of speed, musicality, and clean output. The difference is one of capability within the range. As you move up from the S/550 to the S/850, the larger active driver and the Class A/B amplifier deliver more output and greater ease in demanding rooms. Choose based on the demands of your speakers and space rather than on a notion of one being superior.

Which Should You Buy by Scenario

You have bookshelf or compact floorstanding speakers in a small to medium room

The REL S/550 is the natural partner. Its 10 inch driver and deep extension integrate seamlessly without overwhelming the space, and it keeps up beautifully with detailed, nimble speakers.

You have larger floorstanders in a medium to large room

The REL S/850 gives you the extra output and effortless authority a bigger room and bigger speakers deserve, while preserving REL's signature music integration through the High Level connection.

You prioritize two channel music

Either model excels here thanks to the High Level connection. Match to your speakers and room: the S/550 for smaller systems and spaces, the S/850 when your mains are larger and the room is more generous.

You prioritize home theater but still care about music

Both offer a dedicated .1/LFE input for bass management. For big rooms and impactful low frequency effects, the S/850's greater output is the stronger fit, while the S/550 serves smaller theaters with plenty of clean slam. If your system is dedicated purely to home theater and music integration is not a concern, ask us about REL's HT series as well.

You want the largest soundstage and maximum output

Consider running two RELs in a stereo pair or line array. Two matched S series subwoofers deliver greater output and a larger, more enveloping soundstage. We are happy to advise on stacking a matched pair.

Let AEA Help You Choose

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 us to arrange a listen or to help match a REL to your speakers and room. Whether you are deciding between the S/550 and S/850 or considering a pair, we will help you land on the right sub-bass system for your system and space.

Frequently Asked Questions

Which should I choose if I have bookshelf or compact floorstanding speakers in a small to medium room?
The REL S/550 is the natural partner. Its 10 inch driver and deep extension integrate seamlessly without overwhelming the space, and it keeps up beautifully with detailed, nimble speakers.

Which should I choose if I have larger floorstanders in a medium to large room?
The REL S/850 gives you the extra output and effortless authority a bigger room and bigger speakers deserve, while preserving REL's signature music integration through the High Level connection.

Which should I choose if I prioritize two channel music?
Either model excels here thanks to the High Level connection. Match to your speakers and room: the S/550 for smaller systems and spaces, the S/850 when your mains are larger and the room is more generous.

Which should I choose if I prioritize home theater but still care about music?
Both offer a dedicated .1/LFE input for bass management. For big rooms and impactful low frequency effects, the S/850's greater output is the stronger fit, while the S/550 serves smaller theaters with plenty of clean slam. If your system is dedicated purely to home theater and music integration is not a concern, ask us about REL's HT series as well.

Which should I choose if I want the largest soundstage and maximum output?
Consider running two RELs in a stereo pair or line array. Two matched S series subwoofers deliver greater output and a larger, more enveloping soundstage. We are happy to advise on stacking a matched pair.