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This review first appeared in the June 2012 issue of hi-end hifi magazine of Germany. You can also read this review of the KEF R900 in its original German version. We publish its English translation in a mutual syndication arrangement with the publishers. As is customary for our own reviews, the writer's signature at review's end shows an e-mail address should you have questions or wish to send feedback. All images contained in this review are the property of fairaudio or KEF - Ed.

Reviewer: Markus Sauer
Sources: Digital - Heed Obelisk transport/DAC; analogue - Garrard 401 in Loricraft plinth, Alphaso HR100S tone arm,
Ortofon Cadenza Black cartridge, Tom Evans Audio Design The Groove Plus SRX phonostage
Amplification: Tom Evans Audio Design The Vibe with Pulse power supply, Bryston 4B SST, Symasym
Loudspeakers: JBL LSR 6332
Review component retail: €3.598/pr

R for reference?
Last year KEF celebrated their 50th anniversary. Founded in 1961 by Raymond Cooke—one of the grand old men of British hifi—drivers like their B139 woofer, B110 mid/woofer and T27 tweeter often became legendary to establish a brilliant reputation for the brand which continues today. The B110 and T27 for example appeared in British speaker icon BBC-Monitor LS3/5A which was built under KEF license. I too have to thank KEF for one of my earliest encounters with ‘serious’ hifi. A student-day buddy who bunked in the same dorm quarters owned a pair of 104aB. They were the product of KEF's dominant technical director Laurie Fincham who revolutionized the hifi world of his day by applying digital measurements for speaker design.

Since 1992 KEF is a Chinese-owned example for how clever and respectful management of a brand's identity paired with modern production and far-reaching innovations can bring a company to bloom. Design and engineering of KEF products remains as always in Maidstone/UK. The original development of KEF’s Uni-Q driver concept where a tweeter sits in the acoustic center of the midrange cone dates back to Fincham’s tenure. His 1988 advance was made possible by the first availability of a then mostly unknown magnet material with stunning field strength – neodymium.

Obviously the coaxial driver principle is no KEF invention. Fellow brits Tannoy have employed it since 1947 but their alignment places the tweeter’s magnet and thus also its acoustic center behind that of the midrange. It’s why historic Tannoy crossovers always had a delay circuit built into their low-pass leg. KEF’s contribution to the art was placing  tweeter and midrange voice coil in one location.
Hence the Uni-Q driver isn’t merely coaxial but coincident to enjoy advantages in the crossover region. Again KEF aren’t the only firm to recognize such coaxial benefits and many others since rely on them. By design this includes today’s review subject, KEF’s R900.

Introduced in 2011 the R Series adopts the latest gen Uni-Q from the Blade flagship - and essentially unchanged. The R900’s midrange diaphragm runs the same liquid-crystal polymer with rib stiffeners and a folded so-called Z-Flex surround to minimize reflections in the membrane/chassis transition. There’s also a "Cone Breakup Control" feature, apparently a kind of rubbery interface between cone and voice-coil former. Enlarged over the predecessor this voice coil terminates in an aluminium ring to lower self inductance and eliminate magnetic coupling between mid/tweeter voice coils. The combined goal of these solutions is midrange cone breakup well past the 2.9kHz filter frequency.

Like that of the Blade and costlier Reference Series models, the tweeter housing terminates in a sealed pipe similar to B&W Nautilus designs which exhausts/absorbs the driver's rear emissions. The tweeter cone is reinforced with a secondary element to push its first resonance mode well past the limits of human hearing says KEF.

The bands covered by the Uni-Q driver thus approach the point-source ideal. Properly managed—here the ‘Tangerine Waveguide’ acts as acoustic lens whilst doubling as protection against mechanical damage—such a radiation pattern exhibits constant off-axis attenuation. This avoids the inherent beaming at the upper edge of the midrange driver whose radiation otherwise broadens noticeably at its lower hand-over transition to spray more acoustic energy at the sidewalls. This effect often creates a subjective presence-region emphasis even with speakers measuring admirably linear on axis. My sonic descriptions will present evidence whether KEF hit their self-imposed aim. The membrane of the two 20cm woofers is a hybrid of outer cellulose and inner aluminium by the way.