The story’s been often told: 30 years ago, British speaker manufacturer KEF was asked to design a small, spherical loudspeaker that could be used in a European project to research room acoustics. The speaker had to have wide, even dispersion, so KEF’s solution was to mount the tweeter coaxially, on what would have been the woofer’s dustcap. That “point source” drive-unit, called the Uni-Q, began appearing in KEF’s commercial speaker models in 1989, starting with the Reference 105/3—but it wasn’t until the appearance of KEF’s 50th-anniversary loudspeaker, the LS50, that I felt that the Uni-Q drive-unit had fully fulfilled its promise, at least in a speaker I had auditioned in my own room.
The LS50’s driver was derived from the Uni-Q model used in KEF’s full-range flagship, the Blade ($36,399/pair). Though I had listened to the Blade at shows, at 1.4 metres tall, it was probably going to be too large to work optimally in my room. But when I heard, at last October’s New York Show, that KEF was about to introduce a slightly smaller version, the Blade Two ($36,399/pair), I asked for review samples to be delivered as soon as they became available.
The Second Blade
An examination of the Blade Two gives an overall impression of elegant and effective audio engineering.
At 1.4 metres tall, the Blade Two is only slightly shorter than the original Blade and shares its form factor: an idiosyncratically shaped, parabolically curved enclosure designed by Eric Chan, of New York-based ECCO Design. This is formed from high-density polyurethane that, with a stretch of the imagination, resembles a knife blade, hence the name. The elegant cabinet is no wider than it needs to be, and is shallower and narrower at the base than higher up. It is therefore supported on a wide plinth. The plinth has a spirit level at its rear, and can be fitted with carpet-piercing spikes.
The Two’s complement of drive-units is similar to the Blade’s: an advanced development of KEF’s Uni-Q driver is mounted in a shallow recess on the front of the speaker. Whereas the LS50’s Uni-Q has to operate full-range, and the 5″ cone therefore must be able to undergo significant excursion, the Blade Two’s Uni-Q is crossed over at 320Hz. This means that a different surround, optimized for high-frequency operation, can be used, but other than that, the Blade Two’s midrange cone looks similar to the LS50’s: both are formed from an aluminum-magnesium alloy, but the Blade’s has a ribbed skeleton attached to the rear of the cone and a 3″ voice-coil, which pushes break-up modes as high in frequency as possible. The die-cast basket of the drive-unit’s chassis is profiled to present the smallest degree of acoustic obstruction behind the cone.
The 1″ aluminum-dome tweeter, vented to its rear, is mounted at the exact acoustic center of the midrange cone. It takes over above 2.4kHz and has a dual-profile dome, elliptical at the base for maximal stiffness—which pushes the primary dome resonance up to around 40kHz—but with a spherical cap to optimize dispersion. KEF’s patented “tangerine” waveguide is mounted in front of the dome; this and the profiles of the midrange cone surrounding the tweeter, the drive-unit’s surround, and the its recessed, flared mounting plate, plus the profile of the enclosure, all contribute to optimal control of the Blade Two’s high-frequency dispersion.
Low frequencies are covered by two pairs of woofers, mounted on opposite sides of the enclosure and with their chassis coupled together to cancel reaction forces that would otherwise excite enclosure resonances. However, whereas the Blade’s low-frequency drivers are each 9″ in diameter, the Blade Two’s are 6.5″. The woofer cones, formed from aluminum, have a shallow concave profile, and each opposed pair of bass drivers is mounted in a discrete, ported chamber separated from the other pair by an internal partition, this construction said to increase the frequency of any internal standing waves beyond the crossover point. Two large-diameter ports vent to the enclosure’s rear.
The Blade Two’s crossover filters are said be “simple, low-order” types using “the best components available, carefully selected by a rigorous auditioning process.” Rather than being mounted on a conventional circuit board, these crossover components are hardwired. Electrical connection is via two pairs of WBT binding posts, to allow biwiring or biamping. For single wiring, which was how I used the Blade Twos, patented linking plugs are screwed in between the WBT terminals.
The first recording I played through the KEFs after optimizing their positions was a charming disc of Romantic waltzes Kal Rubinson had given me, with the Orchestra de la Suisse Romande conducted by Kazuki Yamada (SACD/CD, Pentatone PTC 5185 518). The orchestral balance of the SACD layer was rich and full, if sounding undoubtedly more mellow than through the DALIs. But the stereo imaging was superbly precise and stable. In oboe-and-violin duet in the waltzes from Richard Strauss’s opera Der Rosenkavalier, the image of each instrument was appropriately small compared with the orchestral backdrop, yet not obscured in any way.
And like its small sibling, the LS50—which I described in my review as “one of the finest speakers at reproducing female voices that I have heard”—the big Blade Two, too, loved the female voice. I recently treated myself to the live recording of Russian soprano Anna Netrebko singing Strauss’s Four Last Songs, accompanied by the Staatskapelle Berlin conducted by Daniel Barenboim (CD, Deutsche Grammophon 479 3964). I initially felt that Netrebko’s opera-gestated vibrato was too deep for this music, but her voice has a molten-metal quality that draws the listener into her performance and that the Blade Twos faithfully reproduced. In the final song, “Im Abendrot” (At Sunset), Strauss’s sensitive scoring paints a rich-toned soundstage above which Netrebko soared in contemplative calm, without the KEFs editorializing in any way. And again, the image of the solo violin in the third song, “Beim Schlafengehen” (Going to Sleep), was the correct size, and stable. Magic music. Magic speakers.
In the 1970s and early ’80s I was never a fan of KEF speakers, feeling they sacrificed musical involvement in favor of tonal neutrality, resolution in favor of not wanting to offend. A colleague at Hi-Fi News & Record Review, the late Geoff Jeanes, had bought a pair of the original KEF Reference 105s when that speaker was launched in 1977, and too much of the time I listened to the R105 in his system, I found it just too polite. It wasn’t until 1986 and the appearance of the Reference 107, the very last product I reviewed for Hi-Fi News before joining Stereophile, that I felt KEF was managing to marry resolution to an absence of coloration.
The Blade Two carries that evolution to the limit. It preserves all the positive qualities that made KEF’s little LS50 Stereophile’s “Product of 2013,” while adding greater dynamic range and two more octaves of bass extension—though at $36,399/pair, this is for a price more than 16 times greater! The low frequencies are balanced to be neutral in a room larger than mine, though too large a room and the top octaves might start to sound mellow—which could be a concern, considering how sweet they already were in my room. But that imaging magic and its midrange clarity make the Blade Two a winner all the way.
For the full review go to Stereophile.com