REL Acoustics S/550 Closed Box Front-firing Active Driver, Down-Firing Passive Subwoofer

REL Acoustics S/550 Closed Box Front-firing Active Driver, Down-Firing Passive SubwooferS 550 S 550 redefines power and finesse in a compact cabinet, pairing a 550 watt Pure Class D amplifier with advanced CarbonAlloy drivers to deliver speed, scale, and dynamics. Premium Wood Grille orders ship the week of December 20th. Features 550 watt Pure Class D Amplifier 10" CarbonAlloy Active Driver with 12" Down Firing Passive Radiator Music & Theater Systems, Medium Rooms Stereo Pairs & Line Arrays Optional Premium Wood Grille Available. As a

S/550

S/550 redefines power and finesse in a compact cabinet, pairing a 550-watt Pure Class D amplifier with advanced CarbonAlloy™ drivers to deliver speed, scale, and dynamics.

Premium Wood Grille orders ship the week of December 20th.

Features

• 550-watt Pure Class D Amplifier
• 10" CarbonAlloy™ Active Driver with 12" Down-Firing Passive Radiator
• Music & Theater Systems, Medium Rooms
• Stereo Pairs & Line Arrays
• Optional Premium Wood Grille Available. As a natural wood material, grain and color variations are expected and unique to each grille

A Massive Step Forward

S/550 is the gateway to the Serie S line, delivering the speed, depth, and nuance that define REL’s performance ethos. While its larger sibling, the S/850, sets the ultimate benchmark, the S/550 carries forward many of the same design innovations—ensuring the essence of Serie S is fully realized in a more compact form.

The results are remarkable: S/550 offers lightning-fast transients, deep articulate bass, and tonal balance that breathes life into both music and film. Its ability to combine authority with refinement makes it an ideal choice for those seeking a true high-end experience in medium-sized systems, with performance that consistently exceeds expectations.

For those seeking a more bespoke finish, S/550 is available with an optional Premium Wood Grille upgrade for added warmth and individuality.

Designed for Excellence

Take in the design as a whole: horizontal strakes carved into the side walls, elegant elliptical returns that cradle handles finished in a warm golden-silver, echoing raw titanium. Everywhere you look, thoughtful details emerge—but the purpose is clear. This generation delivers the seemingly impossible: a larger cabinet that is lower, wider, and deeper, yet visually lighter.

The added internal volume gives drivers greater freedom and amplifiers improved efficiency, while updated internal bracing keeps cabinet resonances firmly under control. Subtler touches also make a difference, badges that disappear into the grille cloth, silver accents that rest quietly within the cabinet plane, and model numbers etched discreetly into the front rails, visible only when stacked in a Line Array.

An optional Premium Wood Grille adds warmth and individuality, while front-rail leveling adjusters ensure effortless setup, even on uneven floors. Together, these refinements reflect REL’s philosophy that great design is as much about thoughtful usability as it is about beauty and performance.

Drive Faster. Drive Better

The new S/550 10” high-amplitude driver has been completely rebuilt—only the cast frame remains. Its CarbonAlloy™ cone, capped with pure carbon fiber, sharpens attack and smooths decay, letting notes fade naturally into silence. A redesigned suspension allows greater travel, easily handling the amplifier’s added power.

In listening, the driver feels supple and effortless, free from strain. Because it’s lighter, the amplifier works less, yet delivers more power, allowing the driver to move further and play louder than ever before. The result is nothing short of a revelation.

Passive Radiator

Supporting the active driver is an updated and redesigned down-firing passive radiator, purpose-built to handle the extreme throw distances created by the S/550’s upgraded amplifier and driver. Its flat, primary-piston surface, an evolution of carbon, glass fibre, and closed-cell foam construction—is now 40% stiffer and significantly lighter than before. With more than 2.4" (60mm) of travel in each direction, the passive extends dynamics, authority, and depth, completing a system that pushes well beyond expectations for its class

Amplified Excellence

Rated at 550-watts, the Pure Class D amplifier outpaces its predecessor – but numbers tell only part of the story. In our lab, this unit delivers 600-watts continuous with no strain for extended periods of time, not simply for an instant. Its crest power is fully 50% more than its predecessor. It delivers the fast, truly deep bass Serie S is known for, performance that defies spec sheets. Premium polypropylene capacitors, like those used in our Reference models, were installed in our input filters resulting in a more open soundstage with greater transparency. We know from extensive experience that this unit is a rugged and reliable amplifier. As always, fed by our second generation PerfectFilter™, the deep bass is utterly remarkable for a subwoofer whose footprint is so tidy.

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.

Serie S Line Array

REL’s Line Arrays are revered for producing sound staging and dynamics that rival the world’s finest systems. Designed to grow in pairs, a Line Array can begin with a simple stereo pair, expand with a second, and ultimately rise to three units per channel, delivering floor-to-ceiling authority and scale. 

S/550 now features a precision-milled knurled aluminum adjustment knob integrated into the body rails. This knob allows the bottom subwoofer in a Line Array to achieve perfect level on uneven or soft flooring such as thick-pile carpets or dual-pad installations ensuring a safer, more stable foundation. Purpose-built exclusively for Line Array use, these adjustment knobs enable ideal setup and secure performance without compromise. (Note: 212 Black Label does not include these adjustment knobs.)

Wired For Sound…Wirelessly

Sometimes the best wire is no wire. Quality cables are a given in high-end audio systems, but there are occasions where it is impractical, unsafe, or unsightly to drape a cable across the room. REL delivers the ultimate solution with Airship Direct™, our optional wireless system that transmits wide-bandwidth, compound signals, carrying both High Level and .1/LFE simultaneously. Even with the scale and output of S/550, Airship Direct™ preserves the speed, transparency, and authority that define REL. It allows seamless transitions between music and movies without ever touching the controls, all from a single module that plugs neatly into the rear panel and stays invisible in your room. Simple, direct, uncompromised: Airship Direct™.