KEF Blade Loudspeaker (Hi-Fi+)

Standing Tall...

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KEF Blade
KEF Blade Loudspeaker (Hi-Fi+)

Take one look at the KEF Blade and it would be easy to dismiss it as a novelty product – an ostentatious toy for people whose income has outrun their discernment. The Blade might look like a fashion victim’s notion of hi-fi, but both its form and its function are seriously serious. This speaker is all about engineering, a project that has very definitely been built from the inside out.

The Blade has a clearly defined and unbroken lineage, stretching all the way back to the likes of the Reference 104/2 – and beyond. At its heart is the latest generation UniQ driver. Smaller in diameter than early versions of KEFs’ established coincident mid/treble unit, the Blade driver pairs a complex metal midrange cone, formed from ridged lithium/magnesium/aluminium alloy with a carefully evolved aluminium dome that extends response out to beyond 30kHz. The midrange cone is further stiffened by a web of high-tech plastic ribs, bonded to its rear surface, which, together with a massive 75mm voice coil, ensure pistonic motion across (and beyond) its operating range. The striking “Tangerine” wave-guide serves to smooth the dispersion of the driver through the crossover frequency, a concern that extends to the smoothly curved and rubber damped baffle surface that surrounds the diminutive unit.

If there’s not a lot to show for a driver that covers the range from 350Hz on up, below that frequency, the opposite is definitely true. After its sculpted, statuesque shape, the most striking feature of the Blade is the two 225mm aluminium coned bass drivers decorating each side of the cabinet. And it’s not just their size that strikes you, but their position. These are a lot further from the floor than you normally see a bass driver. In fact, look carefully and you’ll realize that they are actually symmetrically disposed above and below the UniQ unit, and as close behind it as possible. What is less obvious is that the motor system on each driver employs a long throw suspension and 95mm voice coil – the size you’d normally find on a 15” unit. The motors are so large that they literally sit back to back across the narrow cabinet, linked in a classic force cancelling arrangement.

Once you opt for a coincident array like this, the rest of the speaker follows from there. The cabinet is constructed from a two-part (front and rear) fibre-glass shell, stiffened with substantial internal bracing. The curved walls are designed to further stiffen the structure, as well as reducing diffraction effects and internal standing waves. The midrange driver enjoys its own, separately molded internal enclosure, while a massively stepped internal brace divides the bass cabinet into two separate and separately ported volumes, further cutting down on parallel surfaces while also reducing the largest cabinet dimension, raising the resonant frequency of the structure well outside the driver pass-band.

The bi-wirable crossover is mounted in a separate section at the base of the cabinet and the whole kit and caboodle rests on a molded polymer foot, fitted with four M8 spikes, adjustable from above using the supplied allen driver. KEF builds a bubble level in the speaker’s foot; there isn’t a level surface anywhere on the cabinet, so some fixed reference is essential. Standard finishes are gloss white or black, but a range of exciting hues are available as cost options.

What KEF has done here is designed and built not just the best UniQ driver yet, but combined with a bass-end that matches it for quality and qualities. The cabinet is surprisingly light yet incredibly rigid, while the back to back arrangement of the bass drivers significantly reduces the energy passing into it. The result is a low storage enclosure with an incredibly low sonic signature. The lack of internal wadding, not required because of the cabinet’s careful shaping, along with the massive motors employed means that thermal or pressure related compression is also vanishingly low compared to conventional systems.

Most speakers rely on boundary reinforcement to deliver deep bass from a manageable driver/enclosure combination. KEFs adherence to the point-source principle means it has to generate bass through sheer swept area. Hence the four bass drivers a side, the massive motors and the relatively modest -3dB point at 40Hz. Not much on paper, but boy, what bass it is!

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Sidebar: Set-Up and System

It’s not just the sound of the KEF Blades that is different; you need to treat them differently too. Positioning a speaker in the listening room is usually about optimizing bass weight, pace and timing – integrating the bottom-end into the whole. With the Blade, positioning is not so much to do with weight; it’s all about the continuity and integration of the soundstage, establishing the spatial relationships between the elements in the band. And by getting the stereo perspective locked in, you are locking in rhythm too.

I worked the speakers backwards and forwards to establish the best placement for bass linearity, using toe-in to focus the soundstage. With the speakers pointing just outside of my shoulders, I then used rake (a small degree of forward tilt) to lock the soundstage together. You may not recognize that description, but believe me, try it and you’ll hear it clearly enough.

The other consideration with the Blades (as with most speakers) is the choice of driving amplifier. A nominal four Ohm load, with a stated minimum of 3.2 Ohms and a 90dB sensitivity, there’s nothing particularly frightening about the KEFs on paper. But, like many really clean, low distortion designs, the Blades go very loud almost without you realizing it. Get carried away and let your enthusiasm outrun the capabilities of the driving amplifier and you’ll hear the tweeter start to shout. Sonically it’s not a massive shift, but what does the damage is the way it forces instruments forward in the soundstage; normally so spatially coherent, anything out of place stands out like a carthorse in the Derby.

I spent a lot of time on this issue as it is the one major question mark over the speaker’s performance, and the conclusion I came to is that while the Blade isn’t blameless, it’s not an inherent failing. I suspect there’s something a little nasty in the impedance load at high frequencies that under extreme conditions drives amplifiers beyond their comfort zone. The evidence for this lies in the fact that it never occurs at lower levels, it never happens with genuinely powerful amplifiers and it rarely happens with a reasonably powerful valve amp, insulated as it is by its output transformer. In practical terms it means that you need to listen to these speakers with your intended amp and be realistic about your material and listening levels. As long as the amp is up to it, you’ll be rewarded with truly exceptional performance.

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One of my favourite tests for bass performance is the Cure’s masterpiece, Seventeen Seconds (Fiction FIX 004). The whole album offers a serious low-frequency workout, but the combination of heavily damped kick drum and the rapid, repetitive notes of the bass guitar line on ‘A Forest’ are a test not just of a speaker’s weight or bass impact, but its ability to delineate individual bass notes. The Blades’ incredibly quick, clean and responsive bottom end allowed it to separate each successive bass note, identifying both its rhythmic placement and pitch. Sometimes, this cut can sound almost lethargic, on other occasions smoothly meditative, but the KEFs instill it with its true sense of urgency and anxious undertones.

This bass performance reflects several aspects of the Blade design: the lack of slowing or slurring effects from cabinet or boundary related non-linearities; the dynamic range and speed of response at low frequencies, delivered by the multiple massive motors on the bass drivers; the lack of thermal compression under continuous load. They add up to one of the most impressively convincing and engaging bottom-ends Although the -3dB spec is modest, the -6dB point is at a much more impressive 28Hz, suggesting that the bass rolls off more slowly than in most reflex designs.

The Blades position instruments with considerable precision, in terms of width, depth and height. There’s no tendency to stack instruments according to frequency, no tendency for louder instruments to shift forward in the mix – unless it’s the electronics doing the pushing. Where the KEF scores is in its ability to float a truly independent soundstage. It may not enjoy the boundary definition of the biggest speakers, but nor dose it suffer the inaccuracies introduced by faking that effect. Instead, the space between and around instruments is beautifully consistent and coherent, ensuring that each and every musical contribution has a place and occupies it.

These speakers drive a simple four beat bar with the impact and purpose of a jack hammer, but they’re equally comfortable unraveling complex be-bop rhythms or bringing a simple voice and guitar track to almost spookily realistic life. Notes are defined by pitch and placement. The KEFs’ spatial coherence rests in their mastery of the temporal domain; they don’t just show you where the musicians were sat, they preserve the precise impact of that layout on the arrival time of what each one plays. 

So often, the true test of a hi-fi system comes down to whether it allows you access to great musical performances, or does it diminish the drama and artistic achievement. When you listen to du Pre playing the Elgar Cello Concerto, it should be an emotional and heartfelt performance; when you listen to Elvis Costello, you should get the edge and attitude in the lyrics, qualities underpinned in the playing; and when you listen to Narcisco Yepes you should marvel at the controlled intensity of his playing. The Blades are truly transparent to the musical performance, but they are also transparent to the driving system.

By now it should be apparent that the KEFs perform well above their price point. Just be aware that as well as sounding like a £50K speaker, you need to treat them like one too, especially when it comes to partnering electronics. At last year’s RMAF, KEF demoed the Blade with Parasound Halo mono-blocs, to considerable effect. Despite their (comparatively) modest price, these amps are long on quality and even longer on power – the perfect recipe for sonic success with the KEFs.

What don’t the KEFs do? Well, as I’ve already stated, they don’t recreate the full, recorded acoustic. But in almost all other respects they are remarkably accomplished. If they miss anything, it’s the last ounce of instrumental texture, but again, that really is only available from speakers that cost many times the KEFs’ price. Above all, their performance is so coherent and well balanced, that their sound is almost inherently satisfying. They are dynamic and rhythmically involving, communicative and capable of considerable musical subtlety.

In an industry faced with indifference, where too many of the opportunities we get to impress, end with a “How much?!?” or a “So what?” – and that’s before we reach the realms of “You’ve got to be joking!” – the KEF Blade genuinely delivers. These speakers wear their heart well and truly on their beautifully tailored sleeve. There’s no such thing as the universal product, and speaker manufacturers know that you can’t please all the people all the time. Nevertheless I think the Blade is a phenomenal speaker system and definitely one that I could happily live with. You might not agree. Listen to the KEF Blade and you might not fall in love – but I can’t believe you won’t be impressed.

TECHNICAL SPECIFICATIONS

Type: Three-way, coincident source loudspeaker system
Driver Complement: 1x 25mm aluminium dome, 1x 125mm Li-Mg-Al alloy midrange with LCP rib reinforcement, 4 x 225mm aluminium bass units in force cancelling pairs
Bandwidth: 40Hz – 35kHz ±3dB, 28Hz – 45 kHz ±6dB
Maximum Output: 117dB
Impedance: 4 Ohms nominal (3.2 Ohms minimum)
Sensitivity: 90dB
Dimensions (WxHxD): 363 x 1590 x 540mm
Weight: 57.2kg ea.
Prices: Standard Finishes (Black or White): £20,000 per pair; Special Colours: £23,000 per pair

Manufactured by:
GP Acoustics (UK) Ltd
URL: www.kef.com/gb
Tel: +44 (0)1622 672261

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