Full “SL” spec 15˝/375mm bass driver. 450W Class G amplifier. Phase adjustment. Variable cut off frequency. Variable gain. Stereo inputs. 6 year warranty.

New Carbon Fibre Woofer Cones have been developed for all models with ultra-high strength and rigidity to accommodate the added power and excursion of the new X+ Series. M&K Sound's proprietary CNC-machined, extruded aluminium Distortion Killer Shorting Rings also guarantee absolute control and distortion-free, exemplary performance in all settings. 

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M&K Sound's iconic Push-Pull subwoofer architecture and "reversed double driver" non-isobaric configuration mean that both drivers in the cabinet are 'exposed' to room air. Consequently, and like the X-Series before, the X+ Series models are effectively two subwoofers in one cabinet enabling a further associated reduction in distortion. This is made possible by having one inverted driver in relation to the other cancelling non-linearities to produce totally symmetric waveforms. 

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The X15+, X12+ and X10+ all feature full 25mm MDF construction and bracing for negligible panel vibrations or cabinet resonances, and increased venting at the base of the woofers mitigates distortion due to air turbulence. These milled cavities also act as convenient carrying handles for installation efficiency

When Only the Best Will Do(But You've Run Out of Room)

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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.

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Perfection Repeated

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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.

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Arrayed for Battle

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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.

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How to Build Up to a Line Array. How to Setup and Dial in a Line Array.

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Amplified Perfection

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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.

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Drive This

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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.

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Total Control

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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.

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Below are three lovely metal toggle switches 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.

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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.