May 25, 2009 Three years of exhaustive research, testing and experimentation has resulted in the KEF Concept Blade loudspeaker. In particular, the loudspeaker showcases KEF’s cutting-edge capabilities and commitment to furthering innovative design.

At the heart of its design is KEF’s single apparent source technology. In producing smooth, even-handed sound, all the drivers in a multi-way loudspeaker must work together, particularly at the crossover frequencies. The tweeter and mid-range in the Concept Blade share the same acoustic center. Formed from a critically braced liquid crystal polymer – a light but very rigid material – it’s backed by a huge three-inch voice coil and a one-inch rear chamber loaded tweeter, the latter helping to provide resonance free operation through its frequency band.

The single apparent source technology incorporated in the Concept Blade works seamlessly with the four newly developed 10-inch woofers employed in the loudspeaker. These side-firing woofers also share the same acoustic center as the mid-range/tweeter, assisting with the smooth frequency response. Like the other engineering principles in this concept design, the woofer arrangement is simple and logical. The arrangements are mounted in both sides of the speaker enclosure in opposed, symmetrical pairs, so their sound can cancel out one another on the inside of the cabinet. To obtain the full benefit of this configuration, the backs of the magnets of each bass driver had to be bonded directly to one another.

KEF do not state whether the woofers are shielded, but even if they are, it’s likely that such strong magnetic fields in close proximity to one another would reduce the responsiveness of the drivers, producing slight coloration that KEF so carefully tries to avoid. We have to trust that this is where the thorough testing and experimentation have come in.

All this technology is housed in a critically curved cabinet constructed from a carbon-fiber, balsa-wood composite found in ultra-high performance cars. Used for its exceptional lightness and rigidity, the parabolic curvature of the cabinet increases its strength, which means sound is only generated from driver movement and not from distortion of the cabinet.

While the design is different, and some would say rather striking, it seems odd to spend so much time and money designing a cabinet shaped from expensive materials in an effort to reduce coloration of the sound from cabinet distortion. Cheaper, more rigid materials are readily obtainable, easier to work with and achieve the same acoustic result of no cabinet distortion. The one thing that Concept Blade’s shaped design doesn't suffer from is internal standing waves: no two internal surfaces are parallel with one another, which is a problem faced by many “shoebox-shaped" speakers.

According to KEF, the Concept Blade features principles and technologies that will be incorporated into future models in its range. Much the same as the loaded tweeter design did from the B&W Nautilus loudspeaker. But like the Nautilus, will the Concept Blade ever see full production? If it’s everything KEF promises, then it’s a strong possibility.

Tim LeFevre