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How New Blade Advances State Of The Art

How New Blade Advances State Of The Art

KEF has launched two new Blade loudspeakers near the top of their outstanding range of loudspeakers (the $225,000 Muon superspeaker remains at the very top). Given the very high quality of some of their affordable models, especially the LS50 Meta, one wants to sit up and take notice when KEF builds speakers at 15 or 20 times the price. The original Blade was reviewed in The Absolute Sound magazine, and we said “How do they sound? In a word: glorious.” KEF now builds on that, significantly.

How New Blade Advances State Of The Art

Critical Background

Audiophiles will be especially curious when the company making a new high-end speaker is a venerable firm like KEF. In our technological age, history seems to matter little, but we should reconsider with firms like KEF. They have a method to make improvements that is worth understanding because it is different.

One could say that KEF is part of the British School of loudspeaker design, but with important twists. The British school made revelatory changes to how loudspeakers are designed and built, so this is not just a convenient way of grouping firms by national origin. The most famous part of the British School is the part anchored by the BBC (British Broadcasting Company). The BBC designed and built a whole host of speakers in the ‘60s and ‘70s that were designed to ensure that recording engineers could make superb recordings. They made breakthroughs in sound quality by using science informed with extensive listening tests by professionals schooled in the sound of live music. There are companies who still build updated versions of these speakers and they have been highly reviewed in recent years.

KEF was formed (1961) before the BBC school took off and has always taken a similar approach in spirit (it was an early licensee for the BBC LS3/5a) but eventually hewed to a more radical approach in practice. KEF pioneered work on advanced materials, time-alignment, low diffraction, rear-wave management, and complex filter networks. If we say that the BBC added the idea of empirical science to the art and hobby of loudspeaker design 50 years ago, KEF has taken that mandate and made it the basis of a company that continues to advance these ideas conceptually. That is, KEF is continuing to expand its scientific roots to build better and better speakers whatever the implications of what it learns about speaker distortions. Computer modeling, introduced by KEF in the early ‘70s, is now foundational.  As well, KEF builds its own drivers, which allows them to take computer-based lab innovations and deploy them in a way that many other brands simply cannot do.

KEF also is part of a British tradition that integrates significant work on industrial design into the building of speakers. Not to be confused with styling, industrial design endeavors to create products where form follows function and applies advanced manufacturing techniques which tend to yield very high acoustic quality and finish precision.

The New KEF Blade One Meta and Blade Two Meta

The new Blade One Meta is a large (62.5 inches tall, 126 lb.) floor standing loudspeaker. The core idea of the Blade One is to be the most extreme implementation of KEF’s Single Apparent Source technology.

How New Blade Advances State Of The Art

The Blade One Meta is priced at $35,000. That’s an expensive speaker, but it places the Blade One in a range that has proven popular with audiophiles who want extreme performance but don’t have the room or budget for superspeakers that can cost ten times as much.

There are several ideas brought together here. In simple terms, we want sounds at all frequencies to arrive at our ears at the same time. In practice, this is difficult to achieve with multi-driver systems that have speakers at different distances from the listener and crossover networks with different phase characteristics at different frequencies. To address this, KEF uses their Uni-Q driver concept to physically align the tweeter and the mid-range. The woofers are then physically designed to be on the same axis as the Uni-Q driver, and the crossover is implemented to align all the drivers. This yields what KEF calls Single Apparent Source. There are very few speakers which achieve this level of time-alignment across the full audio spectrum.

And if you wonder whether aligning the woofers is important (the woofers often left being the odd man out in the alignment concept), consider that middle C on the piano keyboard has a fundamental tone of 262 Hz. In the Blade One Meta, the woofer to midrange crossover is at a 350 Hz. That is relatively low and yet the fundamentals of half of the keyboard are mainly being reproduced by the woofer.

Achieving this time alignment is much harder to do in practice than it may sound, because the crossover has multiple jobs to do and must deal with drivers that do not respond in the same way across all relevant frequencies.

There is more. We want the output of the speaker to be consistent across all frequencies. In practice this is virtually impossible because the speaker diaphragms any manufacturer is using are of a specific size, while the wavelengths being reproduced vary (bass has longer wavelengths than mid-range and treble sounds have even shorter wavelengths). The result is that speaker drivers tend to become more omni-directional as frequencies go down and directional as wavelengths go up. For this reason, designers use tweeters that are smaller and woofers that are bigger. Suffice it to say, getting smooth radiation around the speakers in a real cabinet at a huge range of frequencies is frightfully difficult. KEF clearly has this idea in mind with the Uni-Q/Single Apparent Source concept. This smooth radiation matters because the ear/brain system uses both direct and reflected sound, especially the first reflection point, to determine what is making the sound, its location in space, and its distance. If the reflected sound has a different character (different frequency response if you like) this is to the detriment of imaging and soundstaging. The impressive thing is that KEF has achieved a super-smooth radiation pattern using different driver sizes (see figure).

How New Blade Advances State Of The Art

When reading this figure, concentrate on the dark and medium red areas. Note that the horizontal dispersion is about 100 degrees above 1 kHz and then very smoothly expands to about 240 degrees at 300 Hz. Bass, as in almost all speakers is omni-directional.

And to be clear, there is still more. The more in this case is setting a goal of low distortion. With dynamic drivers in cabinets, one of the problematic elements is that the drivers radiate both front and back. But the back wave essentially has to be eliminated, or it will act as a form of distortion. Here’s where the Meta in the moniker comes in. KEF uses metamaterial behind the Uni-Q driver to absorb the tweeter back wave. The Metamaterial is a complex series of frequency-tuned channels that turn the back wave into heat across a broad spectrum, rather than just using cabinet mass and a simple acoustic fabric to do the job (less well). At the woofer end, KEF has used a four-woofer system to create the physical alignment described above and to have a back-to-back arrangement where the woofer vibrations cancel each other out mechanically. Then a massive, damped cabinet is used, with special shaping to minimize diffraction.

Blade Two Meta

How New Blade Advances State Of The Art

The Blade Two is not a trickle-down product that does a rough approximation of the Blade One to hit a lower price point. Priced at $28,000 per pair, the Blade Two does exactly what the Blade One does in large rooms, but the Blade Two low frequency system is designed to work better in smaller environments. Essentially, room gain will differ between large- and medium-sized listening rooms, and the Blade Two is meant for the latter so that bass overload doesn’t become a difficult issue.

Consider the Blade One Meta and Blade Two Meta to be KEF’s latest work on bringing this all together, remembering that work on the first Blade was begun in 2006 and continued for 5 years before it’s 2011 introduction. KEF has had 10 addition years to work on the Blade and get it even closer to the ideal. The improved linearity (same electrical or acoustic characteristics at all frequencies) in the Blade One Meta and Blade Two Meta are impressive achievements: nearly every parameter got better on an already outstanding speaker.

Read the press release here.

KEF Dealer Listing 

How New Blade Advances State Of The Art How New Blade Advances State Of The Art

Tags: FLOORSTANDING KEF LOUDSPEAKERS

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