KEF Blade Two loudspeaker

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, which I reviewed in December 2012, 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.

Designed by a team led by engineer Jack Oclee-Brown, the LS50 is a superb performer. As I wrote in a Follow-Up review last January, "The KEF LS50 gave a sound that was evenly balanced from the upper bass through the high treble, with superbly defined imaging." But the LS50, a minimonitor costing $1500/pair, is necessarily limited in both loudness capability and low-frequency extension.

The LS50's driver was derived from the Uni-Q model used in KEF's full-range flagship, the Blade ($30,000/pair). Though I had listened to the Blade at shows, at 62" 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 ($25,000/pair), I asked for review samples to be delivered as soon as they became available in the US.

The Second Blade
An examination of the Blade Two gives an overall impression of elegant and effective audio engineering.

At 57.5" 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.

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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.

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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.

Setup & Listening
I began with the KEF Blade Twos in the same positions as the DALI Rubicon 8s ($7995/pair), which had preceded them in my room. Though dual-mono pink noise sounded smooth and evenly balanced, with no frequency regions either being too prominent or splashing to the sides, the low frequencies sounded too loose. I moved each speaker from side to side and forward and back, a half-inch at a time, until I achieved the most even transition between the midbass and upper-bass regions; only then did I insert the spikes in the bases. With the spikes, the Blade Two's tweeter is 39" from the floor, which is a couple of inches above my ears when I sit in my listening chair. However, the character of pink noise changed very little as I moved my head up and down. Its Uni-Q drive-unit gives the Blade Two wide, even vertical dispersion.

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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.

The same impression held when I played "The Mooche," from the Jerome Harris Quintet's Rendezvous (16-bit/44.1kHz ALAC file from CD, Stereophile STPH013-2). The sound was mellower than it had been through the DALIs, especially with the polite-sounding Bricasti amplifiers, which made differentiating Bill Drummond's swishing cymbals in the first verse from the air escaping from alto-sax player Marty Ehrlich's embouchure a little more difficult. But again, the stereo imaging was superbly stable. I had recorded Steve Nelson's vibes in stereo and panned them in the mix from audience left to just left of center stage. Through the KEF Blade Twos, every mallet stroke was precisely positioned in space.

COMPANY INFO
GP Acoustics (UK) Ltd.
US distributor: GP Acoustics (US) Inc.
10 Timber Lane
Marlboro, NJ 07746
(732) 683-2356
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COMMENTS
audiodoctornj's picture

As a Blade dealer who has both the LS 50 and the Blades and the Ref 1 and 3 and the R series, I feel I know the line really, really well.

I agree with many of the comments that were made, however, I was really taken back by the comparison to the LS 50 saying that other than increased bass, and dynamics, you seem to be implying that there is some similarity between the LS 50 and the Blade II.

We love the LS 50 and even with the matching KEF R400 sub woofer the sound is really great, and in fact will challenge a lot of $5k plus speakers, but the resulting sound doesn't come close to amazing resolution, and incredible holographic sound stage, which comes out of the Blades, so it is not just about the increased bass and dynamics, there is a wholeness and organic quality to the sound that you just don't get out of the LS 50 or many other speakers.

We had a setup at the New York High End Show in 2013 with the original Blades setup with state of the art electronics, a Merrill Williams Turntable, and an EMM Labs Digital setup and the system was amazing! Yes this system was over a $100k: $30k speakers, and 50k electronics, and $15k front end plus $20k plus on cables, so the system was up there in price but I did listen to the $107k Yg the $54k Wilson's plus some other very expensive speakers and I would say that a well setup pair of Blades offers the performance of speakers in the $50k-100k price range and that is an amazing value proposition that the Kef Blades and Blade II represent.

w1000i's picture

How do you compare Ref 3 to blades ?

brian_pdx's picture

Would love to hear these speakers although esthetics will take time to get used to. Similar to TT dust covers are speaker grills going away? Dust covers serve a need, make total sense and a well designed speaker grill keeping your 5 year old from putting a PBJ through a woofer makes even more sense.

brian_pdx's picture

Went to an event last Saturday at Echo Audio in Portland where the big Blades were featured by KEF. I was completely taken by the sound, one I had never heard from a home speaker before. For that price you expect it but KEF also demo'd the Reference 1 and the LS50s both of them simply outstanding but the Ref 1 was also driven by the 400W Chord monoblocks. The KEF people said the Ref. 1 could be well driven by 200 W. They also said, to answer my above question, the drivers are very "tough" and hard to damage even without grills. I agree with the reviewer that these speakers are very neutral, source material is important but I cannot get over the way the sound of all three speakers embraced me. At 1/4 the price, the Reference series is actually attainable. But the Blades make me want to buy a lottery ticket. Highly recommended.

Venere 2's picture

Although this review is about the KEF Blade, I have to mention another KEF speaker that is highly recommended.
I had the chance to audition the KEF LS50 speakers. The hype and fanfare surrounding the LS50s is out of this world. The performance is anything but… They are very good, but they don't come anywhere close to what all the hype would have one believe. They are a good buy for their price, nothing more. They absolutely do not belong in Class A!

If the 1500$ KEF LS50 belongs in class A, then what Class for the 25 000$ blades? The first Class A++++ ever for Stereophile?

makarisma's picture

I think they are great as desktop speakers.

scott.w's picture

Hi John,
Chatted with a KEF dealer recently about the Blade Two's. He emphasized they absolutely require top flight amps to make them sing properly. Didn't see that mentioned in this review.

Perhaps the unspoken assumption that pricey speakers = pricey amps? Did you try the Blades with other amp combos out of curiosity?

spudnik's picture

Having read your review I have been left with the frustrating belief that it was incomplete. The problem, as you have no doubt been informed, is that there is no comparison between Blades I and II. The ommission is also obvious: Sterephile did not reveiw the Blade I. I do not know the rationale for that choice but as I have complained before, it was a bad one. You are Stereophile. You ought to have found a way.

WM's picture

I'm guessing the slopes are steep with the side firing woofers, but just wondering if there is any issue with that crossover point and 2pi etc.

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