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KEF R Series Subwoofer Speaker
KEF R Series Subwoofer Speaker 0

KEF R Series Subwoofer Speaker

Model #: R400b
At a Glance
KEF R Series Subwoofer Speaker with twin 9-inch LF drivers powered by twin 250W class-D amplifiers
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Get to know this product.

At just 14 inches square, the KEF R400b may be compact, yet it packs an incredible punch. With a reinforced and braced sealed cabinet, the R400b houses twin 9-inch LF drivers powered by twin 250W class-D amplifiers. The drivers are mounted back-to-back, to create ‘force cancelling’. This means the opposing reactive forces are nullified, resulting in no cabinet agitation and a clean, fast, powerful bass performance – perfect for any serious home theatre system.


  • Enjoy the amazingly fast and clean mid-range response. Listen to startlingly pure high frequencies. Together operating as a single perfectly, integrated voice. It delivers sweet accurate sounds of unprecedented clarity.
  • Unlike conventional speakers, the mid-range cones are rigid magnesium/aluminum constructions that reduce breakup problems. The new mid-range Z-flex surround smooths the tweeter transition to the front baffle, which results in undistorted high frequencies.


  • Dynamic, uncompressed and undistorted bass of heart pounding clarity envelops you, striking deep emotional chords. Your soul will awaken. And the earth will move.

Bass Driver

  • Massive, vented magnet assemblies and large aluminum voice coils drive the lightweight yet stiff, strong hybrid cones. Bass output is faster, cleaner and more accurate. Satin anodized elements contribute to the unit’s elegance, while the diameter of the trim ring accentuates a visual sophistication that belies the speaker’s awesome power.


  • Force cancelling drivers avoid cabinet agitation. Opposing reactive forces are nullified by rigidly mounting the low frequency drivers back-to-back.


  • Designed from the ground up, the R series is a towering leap forward that creates a new dimension in sonic authenticity.
  • The geometry and bracing of the enclosure optimizes vibrational behavior, reducing secondary radiation from cabinet walls for a cleaner sound. Damping panels further minimize cabinet resonance and colouration.
  • Front baffles are clean with no visible screws. Grilles are fixed magnetically. The R Series complements the home as much as it respects the music.


  • Adjustable die cast aluminum feet support steel spikes, with integrated locking knobs for easy height adjustment. Nickel plated bi-wire connectors with terminal linking control allow all standard connection methods and provide easy, reliable connection. The geometry of the reflex ports has been tuned to minimize turbulence at high levels, reducing port noise and low frequency compression.


  • The R Series presents the high-end technologies of KEF Blade in a timeless, elegant format. Serious audiophiles can now enjoy phenomenally accurate reproduction that neither adds nor subtracts from the original recording. Indulge in a near-Reference experience at a price that will also be music to your ears.

Color Finish Available

  • High Gloss Piano  Black; Walnut (Satin); Rosewood (Satin)


Connector Type:Nickel plated bi-wire connectors


Bass Composition:Anodized Aluminum Dome
Bass Size:9


Sold As:Each


Color:High Gloss Piano Black; Walnut (Satin); Rosewood (Satin)

Misc. Specs

Product Weight (lbs.)47.4
Depth (in.)47.4
Width (in.)13
Height (in.)14.4
Manufacturer Warranty1 Year Parts & Labor
WarningProposition 65 Warning for California Residents