REL Acoustics No.31

Precision Refined. Emotion Revealed. Reference-Level Expression.No.31 distills the Reference philosophy into a more compact form, with stunning speed, nuance, and clarity that uncover the emotional truth inside every performance.

• Smooth, authoritative power from a 900-watt NextGen 7 amplifier
• Fast, articulate response from a 12" carbon-fiber driver
• Expanded depth and scale through Line Array compatibility
• REL Reference Remote for in-room tuning control
• 12 coats of high-gloss Piano Black Lacquer finish, crafted to match luxury interiors

• Single Subwoofer
• Stereo Pair
• Line Array

3 Year warranty

Lifetime Customer Support

When Only the Best Will Do

No.31 exists to satisfy the needs of those who crave the finest yet have space limitations. Whilst some can afford our flagship No.32 model, it is larger and deeper than some rooms can accommodate. How can you best deliver No.32’s sound quality, build quality, and thoughtful features with a more compact footprint? Enter No.31.

No.31 exists to satisfy the needs of those who crave the finest yet have space limitations. Whilst some can afford our flagship No.32 model, it is larger and deeper than some rooms can accommodate. How can you best deliver No.32’s sound quality, build quality, and thoughtful features with a more compact footprint? Enter No.31.

Perfection Repeated

No.31 matches No.32’s design stroke for stroke, yet somehow it manages to look more svelte, crouching closer to the floor—almost feline in its grace. The elegant plated handles inset into an ellipse is retained, as is the string grille that permits vast amounts of air to explode into your room without creating noise like cloth grilles can. No.31 features the curvilinear radius to the sidewalls that define both its performance and its character. But the reduction in visual and actual three-dimensional physical mass is remarkable. No.31: when the best must be delivered in a smaller space.

Drive This

The incredible excursion of the 12” pure carbon fibre driver allows it to play as loud as its larger stablemate. Yet, the No.31 possesses the tactility, nimbleness, and attack that only the greatest subwoofers have ever been able to deliver. Also, its sonic signature works in modestly-scaled rooms and with a vast range of fine speakers. The driver is accelerated by a specially wound 3” voice coil driven by a 13-pound magnetic structure; even near its limits, the voice coil remains solidly inside the gap. It is this visceral power, coupled with great delicacy and nuance, that is No.31’s signature.

Amplified Perfection

No.32’s NextGen 7 Class D 1,000 watt amplifier also lives inside No.31, only limited to 900 watts to ensure the perfect complement to the 12” bass engine within No.31. This allows the maximum dynamics to be delivered while ensuring a long, cheerful life for both components. Here too, the LimitLess Limiter,™ which permits the amplifier to tiptoe right up to its limit without audible compression is part of the magic, conveys a rhythmically effortless quality. Also, its dual parametric filters allow precise micro-tuning; the deepest bass is slightly reinforced, while the upper ranges of bass can be gently trimmed to ensure a brilliantly rendered transition from bass to the main speaker. The electronic design of the reference range is itself artistry.

Arrayed for Battle

No.31 permits the same vertically stacked line array as the ultimate No.32. It delivers transformative performance that no competitor has been able to. For those who have been seeking the ultimate musical and theatre experience, Line Arrays unlock the final dimension of system reproduction. Audiophiles have chased three-dimensional sound for years, yet they have missed the simple fact that the height—not the depth—of image is the missing link. By creating products that are designed to be stacked 3 (or in exceptionally tall rooms, 5) units high while retaining individual crossover and gain control of each subwoofer in the array, REL has created a masterpiece that finally delivers what the most experienced audiophiles have been chasing for the past 40 years.

How to Build Up to a Line Array.

How to Setup and Dial in a Line Array.

Total Control

Take control of your No.31 by grasping the REL Reference Remote Control. Immediately, you will be struck by the perfect fit in your palm, the result of careful thought and numerous generations of trial-and-error fittings during prototype development. The second reaction to it is the awareness of its mass, which conveys its quality, permanence, and immutability. It tells you, “I am a thing of substance, of quality. Pay attention, what you do next matters.” If you have owned a REL in the past (and fully 90% of Rel Reference owners are), all the familiar controls are right at hand, exactly where you’d want them. High (or low if using active speakers) level gain sits comfortably to the right side, the crossover rests in the middle, and .1/LFE gain is off to the left.

Below are three lovely metal toggle switches that handle the critical setup functions. The remote’s on/off switch is at the bottom. It is both as out of the way as possible and remains on once turned on and in use during setup without being accidentally turned off. In the middle sits the phase control. This is used only initially to determine the correct 0 or 180 degrees of phase. Additionally, the top access to the Dual Parametric EQ-marked with A and B—permits the flattest, deepest bass and, at the other end of the bass frequencies, the fine-tuning of crossover behavior. This gives you the perfect blending of subwoofer to main speakers and any vestiges of room-generated boom and resonance can be gently trimmed away.

REL’s Reference Remote reminds you of the perfect butler—always immaculate, indispensable when called upon, then quietly set aside until a future time when perhaps additions or further improvements to one’s system further require its services.

Some systems demand scale balanced with restraint — where the space calls for nuance and proportion. The REL No.31 was created for exactly this moment.

Every bit a Reference Series subwoofer, the No.31 delivers depth, speed, and seamless integration, but in a more compact form ideal for rooms where intimacy and balance are paramount.

Its custom 12-inch driver delivers bass with clarity and control, powered by a 900-watt amplifier that preserves dynamics even at low levels. A carefully tuned cabinet allows low frequencies to unfold naturally, adding weight and definition without overpowering the room. The No.31 is not a scaled-down sibling — it is a purpose-built solution, offering the same precision and musical truth as the No.32, in perfect proportion.

This is where restraint meets refinement. This is No.31.

REL’s Reference Series — the No.31 and No.32 — are designed without compromise, serving as the foundation for the world’s finest audio systems. These are not scaled-up versions of other models, but purpose-built instruments with custom alloy drivers, ultra-fast analog filters, and high-current amplifiers delivering 900–1000 watts of effortless control.

Every element, from hand-finished, internally braced cabinets to lightning-fast transient response, is crafted to integrate seamlessly with reference-level loudspeakers. What sets the Reference Series apart is not sheer output, but execution — bass delivered with texture, space, and finesse. They disappear into the system while expanding the soundstage, grounding silence, and revealing the full emotional weight of music.

In systems where nothing else is compromised, the low-frequency foundation shouldn’t be either.

The REL No.31 is outstanding for both music and movies, combining speed, control, and seamless integration. It brings music to life with natural depth and realism, and in stereo pairs creates a wide, immersive soundstage where instruments and voices feel strikingly lifelike.

For movies, the No.31 delivers powerful, room-filling bass and explosive dynamics while maintaining refinement and balance. It is the ideal choice for those who want cinematic thrills without sacrificing REL’s heritage of musical excellence.

The REL No.31 and No.32 are fully compatible with the Airship II wireless system, engineered to meet the exacting standards of reference-level performance. Operating on a zero-compression 5.8 GHz connection, Airship II transmits both high-level and LFE signals simultaneously, preserving the speed, dynamics, and tonal accuracy REL is known for.

The result is seamless integration and lightning-fast response, without the limitations or clutter of long cables. Whether in a high-end stereo system or a world-class theater, Airship II delivers the freedom of wireless with the precision of a wired connection.

The REL No.31 is well suited for medium to large rooms (250–800 sq. ft.), but room size is only a guide. Its true measure lies in the experience it creates when paired with refined loudspeakers.

In stereo pairs, the No.31 delivers expansive scale and commanding depth, with the speed and control to blend seamlessly into any system. Advanced engineering ensures effortless authority and a natural sense of realism, filling the room with bass that is both powerful and perfectly integrated.

Yes. One of the most advanced features of the Reference Series is the ability to stack the No.32 in vertical Line Arrays, typically three units per side.

Stacking isn’t just about more bass — it mirrors how low-frequency energy behaves in live acoustic spaces, radiating vertically to fill the room from floor to ceiling. A Line Array creates a uniform, immersive wavefront that reduces room interactions and brings the system closer to the feel of a live performance.

The result is not only deeper, more consistent bass, but also greater clarity, openness, and scale across the system. Instruments sound more grounded, voices more present, and the soundstage expands in all directions. As rooms or systems grow, Line Arrays provide a path forward — preserving balance, finesse, and authority at any scale.