Some speakers sure know how to make an entrance. They just have a presence when you first encounter them. I know that’s how I felt when I crossed paths with the KEF LS50 a few months ago. At a glance, this two-way bass-reflex compact looks like little more than a stout box-speaker from an indeterminate era—as simple as it gets. But then you realize you can’t take your eyes off it. Designed to celebrate KEF’s 50th anniversary, it tips its hat to the BBC monitors of the 70s. But the LS50 is not an exercise in nostalgia. It bears zero resemblance inside or out to the birch-ply two-ways of that era—popularized by Spendor, Rogers, Harbeth, and, of course, KEF.
Beyond its modest silhouette, KEF has designed the LS50 with enough innovations to stuff a piñata. It’s visually striking with its high-gloss finish and the KEF logo discreetly etched onto a corner of the top panel. The pink-gold (a nice 50th Anniversary touch) diaphragm of the Uni-Q driver is a pure KEF-designed coaxial unit and the star of its current generation of speakers. Bearing little relation to the deep-throated coaxials of yesteryear, KEF’s latest-generation coincident was designed particularly for the LS50. It’s positioned dead center in a radically curved one- piece front baffle—an incredibly dense, plastic compound which tapers to softly rounded edges.
According to the design team, the 5.25″ magnesium-aluminum alloy midrange driver uses a mechanism to damp diaphragm resonances, so the usual peak in response common to metal cones is ameliorated. According to KEF, the now-familiar “tangerine” waveguide uses radial air channels to produce spherical waves up to the highest frequencies—and this allows a deeper “stiffened dome” diaphragm that raises the first resonance, culminating in response that extends beyond 40kHz. Collectively these technologies ensure wide and even dispersion without interference between drivers.
Despite the LS50’s obvious physical differences from the Blade, these speakers have much in common. KEF has applied many of the same engineering principles for coincident-driver technology, internal damping, and innovative baffle design. The unique curvature and composition of the baffle is directly related to the Blade project and is designed to mitigate diffraction effects and spurious reflections—keys to good soundstaging and imaging. The elliptical reflex port is offset in an upper corner of the rear panel. Its profile reduces high-level turbulence—sources of compression and distortion. The ribbing associated with the Z-Flex surround ensures that the surround does not cause any excessive discontinuity for sounds radiated from the high- frequency driver.
The enclosure, including baffle, is as non-resonant as I’ve experienced at this level. Cabinet construction is all MDF, but KEF analysis has optimized placement of the internal bracing. Add to that the constrained-layer damping placed between the internal bracing struts and the inner walls of the cabinet, and the term “acoustically dead” has rarely been more applicable.
When sizing up the potential of a coincident-driver eleven- inch cube like the LS50, one might assume that it would likely be a “voice” speaker—something more akin to a bridge monitor with distinct, perhaps even serious, wideband limitations. But this isn’t the case. Even under levels of dynamic stress that would send a lot of other mini-monitors heading for the hills, the LS50’s output is remarkably even. It hardly flinches, even when it’s pushed hard. This is impressive, but high output alone is not much of a trick for small speakers nowadays. What is much rarer is high output with linearity and extension.
Sonically the LS50 doesn’t suggest the lighter, faster, and edgier personality of the average compact with a five-incher for a driver. This is an essentially neutral monitor throughout the mid-range. But there’s also a prevailing sweet- ness, a harmonic saturation that lends it a dark, velvety overall character, and a bloom that is so pleasing that I began affectionately dubbing it the butterscotch sundae of small monitors.
When listening to a variety of symphonic music I noted image focus was excellent, as I’d expected from a coincident driver. But it’s not hyper-focused. It provides a more spacious, open, and, in my view, authentic representation of an orchestra. Yes, the LS50 has quick transient reflexes, but that is not what grabbed my attention. Rather, it was its bloom and tonal weight. Heavens to Betsy, this little speaker has guts. As I listened to the Rutter Requiem [Reference Recordings], overflowing with the huge Turtle Creek Chorale and the massive voice of the pipe organ, the LS50 supplied a rich impression of large-speaker grandeur (although somewhat scaled back) as it energized the room with ambience and provided the illusion of the walls fading away as the musicians begin to materialize.
The mid- and upper-treble range is smooth; the sibilance region is controlled— crisp and clean, but with compliance. As I listened to the Bryn Terfel and Renée Fleming duet on “Not While I’m Around” from Under the Stars [Decca], I felt the physical presence of these superb singers, their voices seamlessly expressed. Their images were pitched slightly forward, but only enough to grab your attention and not enough to overwhelm or minimize the musical accompaniment. There is probably a hint of energy fall-off in the presence range, which, when combined with the heavier low end, adds a darker hue to vocals and ever so slightly rounds the edges from peakier recordings. As I listened to Leonard Cohen’s “Darkness” from Old Ideas [Sony], I keyed on Cohen’s voice, whose deep, tired, full-chested character seems dredged from the bottom of an old whisky bar- rel. Here it sounded even darker than usual, as if it had further sunk into his chest.
Ultimately, when pressed at higher volumes, the LS50 will give away some of the finer low-level details. I felt that during the Bach Toccata in C [RCA], Kissin’s piano sounded slightly dampened during high- pursuit lines.
As Kissin’s left hand descended into the lower octaves there was a trace of soundboard plumminess that suggested the presence of a hard-working port. As with the Leonard Cohen example, the 12-string guitar that ushers in “All Things Must Pass” from Concert for George receded slightly in the mix, and during Jen Chapin’s ReVisions [Chesky] baritone sax and acoustic bass shed some weight and developed a more strictly midband character.
The heretic in me should add that owing to the wide dynamic and spectral envelope of the LS50, it’s a very satisfying companion when pressed into home-theater mode. I tend to break in speakers with all kinds of material, so if there’s a Blu-ray movie I’ve been angling to watch, whatever speaker I happen to be running-in will be pressed into duty. In this case, the soundtrack to Wes Anderson’s Moonrise Kingdom, which features Benjamin
Britten pieces and Britten-inspired pieces from Alexander Desplat and Devo’s Mark Mothersbaugh, and further contributions from Leonard Bernstein among others, proved to be a lush romantic workout for the KEFs, with terrific orchestral and percussive selections that exploited the speaker’s dynamic range and vivid timbral colors. Not to mention excellent dialogue intelligibility, with no subwoofer or center channel required.
Throw anything at it, the LS50 takes on all comers.
The LS50 is tuned for smaller rooms and is meant to take advantage of the room gain that can give mid- bass response a boost. However, there are always exceptions, and KEF provides elliptically sculpted foam plugs that are effective in reducing bass output a few decibels. These can be helpful in troublesome situations where the speaker setup is optimized for soundstage and imaging but where the room itself is over-boosting LF output, thickening the bass and thus masking details in key regions of the frequency spectrum.
The KEF LS50 is one of the most all-around-satisfying little speakers I’ve reviewed in some time. Construction and execution are exemplary. It delivers the kind of performance that deserves to be on a Wheaties box. And there’s an incalculable coolness factor that makes it a breath of fresh air. The LS50 also answers the classic question, “Who says you can’t teach an old box new tricks?”
SPECS & PRICING
Type: Two-way bass-reflex mini-monitor
Drivers: Uni-Q array, 1″ tweeter, 5.25″ mid/bass
Frequency response: 79Hz–28kHz (47Hz-45kHz, -6dB)
Nominal Impedance: 8 ohms
Dimensions: 11.9″ x 7.9″ x 10.9″
Weight: 15.8 lbs.
GP Acoustics Inc. (U.S. Distributor)
10 Timber Lane
Marlboro, New Jersey 07746