KEF Launches LS50 Meta and LS50 Wireless II Loudspeakers with ‘Metamaterial Absorption Technology’

In early September of 2020, the British speaker manufacturer KEF announced that a 2-year research and development collaboration with a company called Acoustic Metamaterials Group (AMG) had been buzzing along behind the scenes, and that the fruits of this endeavor would soon be revealed as part of a new loudspeaker design. The two firms developed a world-first application of Metamaterial Absorption Technology (MAT), creating an intricately-designed acoustical device to work as a sound absorber inside a speaker cabinet. Many loudspeakers use materials like wool or foam inside their cabinets to absorb some of the sound created by the rearward motion of the drivers. The forward motion of the drivers is what creates the sound waves that we want to hear — the sound that’s launched into the room from the front of the drivers. But every time the driver moves forward, it must then move backward, and this backward motion launches sound from the back of the driver into the speaker’s cabinet. This sound can create all sorts of problems as it bounces around inside the cabinet. It can reflect back onto the driver itself, causing audible and measurable distortion. It can excite the cabinet, causing coloration that can affect imaging and limit the speaker’s ability to “disappear” into the soundstage. Internal standing waves can build up inside the cabinet and wreak havoc on both the driver’s motion and the cabinet’s vibrational behavior.

The use of sound absorption material can mitigate these negative effects, but existing fibers and foams only absorb around 60% of the energy in question. That’s where metamaterial comes in. Together with AMG, KEF has developed what they call a synthetic material or “metamaterial” — though it’s perhaps more accurate to describe it as a carefully-designed acoustical structure — that can absorb nearly all of the unwanted sound radiating from the rear of the driver. KEF describes the Metamaterial Absorption Technology as “a highly complex maze-like structure, where each of the intricate channels efficiently absorbs a range of specific frequencies. When combined, the channels act as an acoustic black hole, absorbing 99% of the unwanted sound, eliminating the resulting distortion and providing a purer, more natural acoustic performance.” While most acoustic absorbers can only address a narrow band of frequencies, this metamaterial absorbs everything from 620Hz to well beyond the limits of human hearing at 20,000Hz. To put it simply, the sound coming from the back of the driver (the tweeter, in this case) is funneled into the maze-like structure, where the 30 different tubes act as sound absorbers for different frequencies. Sound goes in, and virtually nothing comes back out.

A metamaterial is a material that we synthesize that has properties that we can’t find in nature. In acoustics we use a lot of natural materials to absorb sound — foams or wadding — so we can’t have a lot of control over what they do. We just can select them. The idea of a metamaterial is that, rather than trying to find a natural material that does what you want, you create an object that behaves like the material that you really need.

— Dr. Jack Oclee-Brown, Head of R&D at KEF

Metamaterial the Next Breakthrough in Loudspeaker Development?

According to KEF, Metamaterial Absorption Technology is a major breakthrough in loudspeaker design. Usually when a company like KEF spends years developing a groundbreaking new technology, the first products to reap the benefits are its top-of-the-line offerings. When I read the announcement about MAT, I expected that a new version of KEF’s flagship Blade speakers ($32,000/pair) would be announced first, and that maybe the MAT tech would trickle down into more affordable speakers over time. So I was very surprised when KEF announced that the first speakers to feature its Metamaterial tech would in fact be the new LS50 Meta ($1,500/pair), and the all-in-one active streaming version, the LS50 Wireless II ($2,500/pair). But when you think about it, this approach makes sense for KEF. The LS50 has been one of KEF’s best-selling speakers of all time since it was launched in 2012 as a limited-edition anniversary product to celebrate the brand’s 50th year. It has become truly iconic in the audio industry, and is universally respected. Even Stereophile’s John Atkinson, who regularly reviews speakers with 5- and 6-figure price-tags, uses the LS50 as his reference. If you’re KEF, how do you follow an act like the LS50? You need to bring something really special to the table. The new LS50 Meta not only adds Metamaterial Absorption Technology, but also introduces a number of other advancements that KEF has made over the last 8 years. The concentric Uni-Q driver in the LS50 Meta is the company’s latest 12th-generation design, featuring the tweeter-gap damper first introduced in the 2018 R Series, which “mitigates the negative acoustic effects of the small channel of air between the coaxially mounted midrange cone and tweeter.” The new cone neck decoupler and motor system are “precisely shaped to reduce high-frequency distortion in the mid-frequency driver.” KEF has also further optimized the flare and profile of the patented, off-set flexible port, using Computational Fluid Dynamics (CFD) to calculate the most effective shape for delaying the onset of turbulence, thus preventing resonances from interfering with midrange performance. The cabinet of the LS50 Meta features more rigid cross-bracing than that in the original LS50. Best of all, the LS50 Meta costs the same $1,500 per pair that the original LS50 sold for in 2012. The LS50 Meta is available in 4 new matte finishes (as seen in the main photo above): Carbon Black, Titanium Grey, Mineral White, and a special edition Royal Blue.

Kef Takes Streaming to the Next Level

The all-in-one LS50 Wireless II is an active version of the LS50 Meta, featuring all of the same acoustical advancements. While the LS50 Meta is a traditional passive loudspeaker, the LS50 Wireless II has streaming functionality, digital-to-analog conversion, and amplification all built in. At $2,500 per pair, the LS50 Wireless II costs $300 more than the original LS50 Wireless did when it was introduced in 2016. But it also sports some important new features, including a brand new wireless platform, built around a much more powerful streaming board. The KEF Connect control app has also been rebuilt from the ground up, and now boasts Sonos-level user-friendliness, both for initial setup and for daily use. Unlike the original LS50 Wireless, the new version is fully Roon Ready, and offers MQA decoding and rendering, along with support for Apple AirPlay 2 and Google Chromecast. Spotify Connect is also present and correct. These certifications don’t come cheap, and likely contributed to the $300 price increase, but they’re appealing to customers who are focused on streaming audio, and that is precisely the demographic that the LS50 Wireless is designed for. The LS50 Wireless II also has new, more powerful amplifiers built in, with a 100-Watt class A/B amp for each tweeter, and a 280-Watt class D amp for each mid/bass driver. The amps were developed in-house by KEF to mate perfectly with the new Uni-Q MAT driver. The crossover is handled in the digital domain by KEF’s custom “Music Integrity Engine,” a cutting-edge collection of DSP algorithms that deliver better phase performance than the passive crossover network in the LS50 Meta.

New Improved Kef LS50 II Details

The original LS50 Wireless drew some complaints from users (and potential users) who were unhappy that a so-called wireless speaker system required the use of an ethernet cable to connect the two speakers together. The ethernet cable and its 24-bit/192kHz interlink are now optional on the LS50 Wireless II, which can instead operate using a wireless interlink between the two speakers, though this connection maxes out at 24-bit/96kHz. The original LS50 Wireless included a USB input for connecting the speakers to a computer. The new version trades the USB input for an HDMI eARC input, allowing the LS50 Wireless II to connect to a user’s TV and become the backbone of a 2-channel home theater. (Subwoofer outputs also make it easy to extend the speakers’ already-impressive bass response.) Optical and coaxial digital inputs are also present, along with an ethernet input for those with questionable Wifi. A 3.5mm stereo analog input allows users to connect analog sources, such as a phono preamp. Analog purists should note that the input is digitized, which of course it has to be, since the speaker’s crossover is performed in the digital domain. But while some may consider this analog-to-digital-to-analog signal path to be less than ideal for spinning vinyl, the DSP-powered audio optimization and hand-picked amplification components in the LS50 Wireless II will almost certainly deliver superior overall sound quality than what you’d get from the passive LS50 Meta driven by a $1,000 integrated amp. Based on my experience with the original LS50 Wireless, I think it’s safe to assume that you’d have to spend a LOT more than the $2,500 asking price of the LS50 Wireless II to put together a competitive stereo system based around the passive LS50 Meta.

The LS50 Wireless II comes in the same finishes as the LS50 Meta, except the special edition blue color is replaced by a special edition Crimson Red finish. Both speakers can be mounted to the optional S2 speaker stands ($450/pair), which come in all the same finishes as the speakers, for a truly custom and unusually stylish look. (Unlike the original LS50 and LS50 Wireless, the new LS50 Meta and LS50 Wireless II both have screw threads in their bottom surfaces, so they can be securely fastened to their matching stands.) I think there’s little doubt that these new speakers will be incredibly successful for KEF, and that the LS50’s winning design and unique form factor will live on for many years to come. KEF has also hinted that the Metamaterial Absorption Technology will eventually trickle up, rather than down, and so will find its way into the brand’s more expensive offerings, such as the Reference Series and Blade Series. It will be interesting to see how the tech can be applied to an even greater extent in a larger speaker, where the increased interior space might allow a larger Metamaterial device to be used — perhaps absorbing the back-wave not only from the tweeter, but from the entire Uni-Q driver array. 

Unless otherwise indicated, this is a preview article for the featured product. A formal review may or may not follow in the future.