KEF LS50 Meta Loudspeaker Review

Does this speaker look familiar? It should. The popular LS50 compact appears as fresh as it did the day it first rolled off the production line in 2011, in celebration of KEF’s 50^th anniversary (founded 1961). You simply couldn’t beat the looks of this squarish two-way, bass-reflex design. Plus, the superb fit and finish of its enclosure made an ideal platform for the space-saving Uni-Q, KEF’s proprietary coincident driver. A decade later, the success of this Editor’s Choice/Golden Ear/Product of the Year recipient has morphed into a full-blown collection that now includes center channels and active/wireless versions.

But ten years is still ten years and a lifetime in the world of audio-product cycles. KEF engineers were aware that its competitors haven’t stood still, either. Rather than taking a winning formula and starting from scratch, KEF chose to innovate its way to a better LS50. To go beyond, and thus, Meta. 

First, let’s revisit the pre-Meta original. Per KEF tradition, the focus of the LS50 revolves around its iconic rose-gold, Uni-Q, coincident tweeter/woofer, a driver that was specifically designed for duty in the LS50. Now in its twelfth generation, it’s positioned dead center in a sensuously curved one-piece front baffle. The mid/bass diaphragm of Uni-Q measures 5.25″ and is made from a magnesium-aluminum alloy. It is installed with aluminum magnet rings to reduce flux modulation, a source of distortion. The 1″, vented aluminum-dome tweeter first seen in the vaunted KEF Blade series uses a similar waveguide design, known as “optimal dome waveguide geometry,” to extend high-frequency response over a wider axis. According to KEF, the distinctive segmented or “tangerine” waveguide uses “radial air channels to produce spherical waves up to the highest frequencies—and this allows for a deeper ‘stiffened dome’ diaphragm, which raises the first resonance, culminating in response that extends beyond 40kHz.” Collectively, these technologies enhance dispersion while reducing driver interference. The crossover point is 2.1kHz and impedance (nominally 8 ohms) never dips beneath a reasonable 3.2 ohms. Still, this is an 85dB-sensitive speaker and benefits from robust amplification with solid power reserves. 

Cabinet construction, as non-resonant as any knuckle rap will tell you, is all MDF, bolstered by optimized internal bracing and constrained-layer damping placed between the struts and the inner walls of the cabinet. The novel curvature and composition of the baffle reduce diffraction effects and reflections.  The elliptical reflex port is offset in the upper corner of the rear panel. The taper of its profile reduces turbulence at high levels, sources of compression and distortion. 

So, what exactly is up with Meta? Acoustic analysis directed KEF engineers to focus their attention on improving the damping characteristics of the LS50. Typically, loudspeaker interiors are lined with absorptive materials (bracing, woolen stuffing, etc.) that damp the cabinet in order to reduce resonances in key frequency ranges and smooth mid and treble frequencies.  KEF rethought this concept and came up with something unique—Meta or Metamaterial Absorption Technology (MAT). Visually, it appears as a disc of a few inches in diameter with a maze-like uneven surface. At a thickness of only 11mm it sits directly behind the Uni-Q basket and magnet surface, to reduce the back wave output from the driver that would otherwise cause—in KEF’s words—“undesirable” cabinet resonances. According to the company’s white paper, the “key aspect of the successful implementation is the optimal coupling between the loudspeaker diaphragm and the metastructure through a specific conical duct.” Meta’s tuned channels absorb 99% of the unwanted sound from the rear of the driver, “achieving almost a near-perfect absorption spectrum starting at 620Hz,” compared to around 60% absorption from loudspeakers using different approaches. Thus, it far exceeds the damping properties of conventional designs. 

Partnering with the room for low-frequency reinforcement is part and parcel of the set-up experience, perhaps most particularly for compact monitors. As most audio enthusiasts are aware, careful positioning is crucial to achieving wide-spectrum musicality. As it happened, I set up the Meta in a different listening room than the last time I reviewed the LS50. Ceilings are taller at ten feet, and overall dimensions are larger; so, the LS50 Meta was being challenged to fill a room of considerably higher volume. Fortunately, this difference only required placement a few inches closer to the back wall. Once that was done, I recouped the sound signature that I remembered from my initial foray with the LS50—a midrange on the warmish romantic side, and a weighty midbass that provides room-filling energy. 

Revisiting a loudspeaker that has consistently beaten expectations long after the original review was published is an interesting proposition. In such instances, I ask myself, “Do my conclusions, be they praise or criticism, hold up? Are they confirmed?” For the LS50 taken as a whole, I’d say yes. This was a speaker that was easy to enjoy and relax with then, just as it is now. It often surprised me with its vitality, authentic midrange, and hell-raising output, all from a package barely a foot tall. Vocal reproduction was especially strong by virtue of the speaker’s unwavering focus and image stability, which cast an almost hypnotic spell over this listener’s attention. And rhythmically it still knows how to cut a rug.

Sonically, Meta technology hasn’t caused LS50 to undergo a Jekyll-Hyde personality shift. It doesn’t reshuffle the deck to that extent. Yet, there was a difference. Meta has produced a more open, more transparent version of the original. The laser-like focus of the Uni-Q has grown more open, and there’s a new-found clarity and image stability. Low-level details and micro-information were more explicitly resolved. Transients were refined but retained the level of attack that suggests the authentic rattle of a snare drum or the percussive crackle of a flamenco guitarist’s rasgueado across the strings. Further, I found that during Norah Jones’ “The Nearness of You,” the singer’s sibilance range was less emphatic, her piano more naturalistic. Bottom line—the Meta version of the LS50 has become less visible as a speaker.

Soundstaging and dimensionality were strong suits for the LS50, but Meta was even more convincing at disappearing from the room. Still, left a bit unresolved was its unremarkable height replication—the loudspeaker’s ability to allow the acoustics and air of a venue materialize into the room. As was the case in the original, there seemed to be a ceiling hanging low over the soundstage. 

Dynamically the Meta finds its sweet spot in the mids and higher octaves, which is another reason it’s at its most electric and lively with soloists and smaller groups at moderate volume levels. But I found its limits during the intro to Mary Chapin-Carpenter’s “Shut up and Kiss Me.” At the point when the full rhythm section kicks in, the Meta lacked the dynamism and drive in the power range to fully crank up the band’s kickass energy.

Midbass resolution, the range beneath a hundred cycles, remained something of a shocker, even in light of the passing years. While there’s no mistaking the LS50 Meta for a multi-woofer floorstander, there’s something remarkable about the impact of the driving and ripping electric basslines, tympani, and kettle drums that KEF manages to achieve within the confines of this little box. I’d have bet that port overhang or some other coloration would creep into the soundscape, but even at moderately high levels, not a whimper.  There are limits, of course, and when the Meta is pushed outside its comfort zone, the soundstage foundation loses some of its definition, and low-level bass cues succumb to some compression A final impression: In listening to the Meta version, I was reminded that nothing that occurs in a loudspeaker happens in a vacuum, that upstream tonal differences modify and refine downstream output. The clarifying effects of the Meta in the upper fundamental and first- and second-order harmonic ranges showered resolution and timbral and textural details down into the octaves below.

Much to the relief of the legions of LS50 owners I’m not going to even hint that they put their beloved originals up for sale. They still have more than enough sonic chops to stand on their own. However, if you’re new to the compact-monitor market or itching to upgrade, it would be serious malpractice on my part if I didn’t encourage you to take a sharp look and bring a keen ear to an audition of the LS50 Meta. It’s no easy task to take a fully formed, class-leading success to the next level, but that’s what KEF has managed to do. Plus, at $1499 for the pair, KEF held the line on pricing. A winner that only keeps getting better. 

Specs & Pricing

Type: Two-way, bass-reflex mini-monitor
Drivers: Uni-Q driver array (concentric 25mm aluminum dome/5.25″ aluminum cone mid/bass)
Crossover: 2.1kHz
Frequency response: 47Hz–45kHz -6dB
Nominal impedance: 8 ohms
Sensitivity: 85dB
Dimensions: 11.9″ x 7.9″ x 11″
Weight: 17.2 lbs.
Price: $1499/pr.

KEF
10 Timber Lane
Marlboro, NJ, 07746
(732) 683-2356
kef.com