April 2020

KEF LS50 Active Wireless Speaker System
KEF's all-in-one bookshelf speakers still tower over much of the competition.
Review By Rogier van Bakel

  I've long had a predilection for prix-fixe meals. And why not? Hacking your own path through the culinary scene is fine, but it might be unwise to turn up your nose at three or four courses pre-selected by a talented chef. I don't presume to know his cooking better than he does, so if he tells me that the suggested dishes are his way of combining quality ingredients, his special skill in preparing them, and a reasonable bill at the end, I'm in.

And so it is with certain all-in-one stereo systems — none more, for my money, than the wireless version of KEF's venerable LS50s.

The powered LS50Ws, like their amp-less predecessors, offer super-braced, beautifully-finished, glossy MDF cabinets, which house KEF's coaxial Uni-Q drivers. So far, so familiar. But then the company rounds out the package with some mighty sweet gear: four built-in amplifiers (one for each driver); plus four very-good-sounding DACs (ditto); plus a generous complement of both analog and digital inputs and outputs. The DACs are 24-bit/192kHz affairs. The tweeters, shaped like lemon juicers, are driven by 30-Watt Class A/B amplifiers, while KEF's ribbed, distinctly-colored mid/bass drivers get their juice from Class D amps that boast 200 Watts each. It's a bit like beholding a clown car: you giddily wonder how such a small thing — the KEF cabinets measure 11.8''H x 7.9''W x 12.1''D — can hold such a lavish promise of entertainment. Unlike the clowns, however, the LS50Ws are no laughing matter.

Consider: Thoughtful DSP options let you fine-tune the sound to your room. Advanced streaming capabilities — Bluetooth as well as Hi-Res Music — are available at the touch of a button. Dedicated smartphone apps allow you to take full control (though not without glitches; more on that later). Just add a source, and you're off. It's an invitation that's hard to pass up. You don't have to decide anything, except what to play. I like it.

Now, I'm not a philistine, I think. Of course I see the appeal of building a small collection of carefully-matched เ la carte high-end gear. It's just that these British beauties make a worthwhile counterpoint. They all but shrug and call the separate-components route codswallop, and then they chortle at the audiophilia nervosa that afflicts many of us. You know that tiresome phenomenon, don't you? Just when the angel perched on your left shoulder whispers reassuringly how lovely your bespoke hi-fi rig sounds, the little devil on the right softly cackles that maybe the amp is a little tubby in the bottom octave. And he adds that surely you can hear that the cymbals on that reference recording have a hint of tizziness; might it be time for, say, better speaker cables?

It never ends. But with a quality all-in-one system, it could.

KEF's "traditional" LS50 speakers started making their way into audiophiles' listening rooms (and hearts) some eight years ago. For just $1500, you got blue-lagoon-like transparency, an earful of seamless sonic coherence, a wonderfully wide soundstage, and some of the best articulation this side of five grand. On the downside, the LS50s demanded to be partnered with some seriously good components, lessening their appeal as a stone-cold bargain. In addition, the lowest frequency they could reproduce with authority was 79Hz (+/-3dB). Output down to 50Hz was audibly present but diminished in level.

The wireless version addresses both of those drawbacks. For the extra thousand bucks ($2500, but easily 20 percent less if you look around), you get the built-in amps, the DACs, the streamer... and the freedom to stop worrying about the quality of your speaker cables.

As for the bass, these powered bookshelf / stand-mount speakers slam satisfyingly deep and hard, down to the mid-to-low 40s. They manage this without resorting to a solution that lesser designers might choose: artificially juicing the bass EQ curve. Somehow, KEF's engineers matched the drivers with the spiffy electronic innards in a way that coaxes honest, taut, considerably deeper bass from the compact cabinets.

Via the subwoofer-out on the back of the main speaker, I did connect a Hsu VTF2-Mk5, turned up only to somewhere between 10 and 15 percent on the volume dial; but I was often hard-pressed to say for sure whether the sub was even in the mix. It's true that when I played a Marcus Miller bass-torture track like the delectable Cousin John, or Kanye West's Love Lockdown (featuring buckets of subsonic bass), the Hsu made its presence known nicely. But for three-quarters of what I listen to, the sub was just about immaterial. That even includes hard-slamming metal-ish albums like Rage Against the Machine's eponymous debut and TOOL's Lateralus, as well as deep-drum recordings such as Emmylou Harris' Deeper Well and Lhasa de Sela's My Name. Bottom (and I do mean bottom) line: with the Hsu switched off, I almost never felt short-changed.

Problems, Solved
The LS50Ws began their triumph in late 2016, so they aren't a new product. Why, then, this review? Why now? Fair question. While the storied British company produced a sonic hit with the powered LS50s, batches of the initial product had quality-control issues. Some early buyers complained of dropouts, network problems, erratic behavior from KEF's v1 app, and more. Revisiting the LS50Ws at a later point in their production cycle would perhaps let us assess if the reported troubles persist.

I stress here that I didn't ask KEF for a review sample, nor did I identify myself as a reviewer when I contacted the company with an operational question (to which I received a prompt, courteous, and correct reply). I purchased my KEFs online from an authorized U.S. dealer, so I got a random set, just as any other consumer would.

To cut to the chase, I had almost zero problems during my roughly two-month review period. I did experience a couple of weirdnesses, such as the left speaker being a bit less loud than the right one when using the TosLink input (easily corrected via the tiny balance knob on the rear of the slave speaker, though I ended up preferring the USB input, which had no such issue). Connecting the LS50Ws to my Wi-Fi network required a few attempts, but nothing worse than the 15-minute struggle with the smart lightbulbs that I installed around the same time. For Hi-Res Music, I'd recommend stringing a CAT-6 Ethernet cable between your router and the main KEF speaker anyway, obviating the need for an over-the-air link.

Since launching the LS50Ws, KEF has improved the user experience through frequent firmware updates. For instance, the system used to go to sleep 30 minutes after the last signal, and some users reported that they had a difficult time rousing it from its slumber. Now you can specify the length of the preferred delay in the phone app, and even set the speakers to never power off automatically at all. Also, these days you can designate the main speaker — the one that has the inputs and outputs on the back, and the small control panel on the top — to be your left channel, instead of the default right. That seems like a small thing, and it is, but I love it. Due to furniture and subwoofer placement, I have limited access to the speaker on my right, so I appreciate the flexibility.

During my extended evaluation, the KEFs sat on the far corners of my desk, on four-inch-tall IsoAcoustics Aperta isolation stands, which I'd placed in turn on four-inch custom wooden blocks fashioned from cherry and red balau by the artisans at Canada's Dyckswood. This raised the coaxial drivers almost exactly to ear level.

I found that tonality- and soundstage-wise, they performed at their peak when I had them toed in but not pointed straight at me. The flex-tubed, oval-shaped ports on the back of the KEFs were about eight inches from the wall; and the front baffles, made from polyester resin with glass fiber and calcium carbonate, and curved to minimize diffraction, stood roughly four and a half feet from my face. In other words, I essentially used the KEFs as nearfield monitors. (The company has called the LS50Ws "monitors" all along, partly in reference to their long-ago predecessor and inspiration, the fabled BBC LS3/5a studio speakers from the 1970s.)

DSP settings in the KEF Control app let you specify whether the speakers are placed on a desk or on stands, how far they are from the wall behind them, how much bass extension you prefer, whether you're using a subwoofer, and other variables. I got that dialed in to my satisfaction in mere minutes, no sweat.

The main music source in my home office is a 2017 iMac running Catalina and outfitted with Audirvana v3.5 — a software player and upsampler that lets me access my Tidal and Qobuz accounts simultaneously. Audirvana also taps into my library of 10,000 or so legacy tracks that I have sitting on an old Apple Time Capsule. I connected an AudioQuest Forest USB A-to-B cable between the iMac and the main KEF speaker (routed through an iFi Audio Purifier 3) and did almost all my listening via the speaker's USB input. Two or three times, I used the system's Bluetooth mode, with my iPhone X as the source. To no one's surprise, I'm sure, the USB route sounded best.

Sound Impressions
From the minute I turned them on, the KEFs put a grin on my face, and they weren't even broken in yet (that took about 30 hours). The coaxial configuration — the KEF tweeter is mounted in the center of the mid/bass driver, so the two share an axis — makes you experience the music as one harmonious whole. Because of this design, minuscule timing differences between the two spooning transducers would have to do with their respective mass and speed, rather than with their physical placement. With the KEFs, I couldn't perceive any timing imperfections at all. The visual that sprang to mind was that traditional driver arrays can be like a quilt, with different pieces prettily sewn together. By comparison, the LS50W speakers are more of a tightly-woven cotton blanket — seamless and organic.

Through the KEFs, on Et Si C'ษtait Vrais Part 1 by Martial Solal's terrific big band, the whimsical interplay between trombone and tuba struck me as timbrally accurate to the point of being stirring (when's the last time you were moved by a tuba?). On the second playback, I got positively slack-jawed when the orchestra bellowed its first big chords and I listened specifically to the decay of the sonics after the hard stops, six seconds and then 14 seconds in. The buttery smoothness of that natural fade, the realism of the space it painted... this from speakers that retail for a grand or two? Unreal. I noted just as happily that the soundstage was eight, nine feet wide. The KEFs easily placed the guitar two feet or so outside the far boundary of the left cabinet, and did the same with the oboe on the right.

The various instruments were a bit diminished in size, but I accept that this is a likely consequence of the nearfield placement. In my experience, positioning speakers further apart, with the listening spot pushed back another four to five feet, renders instruments closer to their physical scale.

The KEFs further impressed me when I listened to Infrared by the Canadian post-grunge outfit Three Days Grace (note: not a Christian-rock band, thanks very much). The track was delineated with sweet slam and definition throughout; via the LS50Ws, the crunchy guitars were easily distinguished from each other even when they were thrashing out the same riff.

I kept hearing instruments and voices rendered with exactitude. The singing bowls and resonant drums on Michael Brook's Albo Gator were true to life, and Lyle Lovett's entire Large Band sounded wildly satisfying on Blues Walk (though that's a low bar; somehow that recording always sounds excellent, even on a beat-up boombox). Billie Eilish's You Should See Me in a Crown stood out on the KEFs for the spine-tingling intimacy of her half-whispered vocals, as well as for the authoritative, throbbing synth lines. Both were presented with sonic aplomb.

The recording I've probably played more than any other this year is Parker Millsap's unbelievably affecting version of an old gospel-blues standby, You Gotta Move. Channeling Robert Plant ca. 1971, Millsap wails like a woebegone banshee, dueling in turns with the harmonica, the bottleneck guitar, and the doleful fiddle — until the four parts end up in unison at the end, signifying surrender and resignation. It's a track that can bring me to tears, and the KEFs never stood in the way of taking me to that place of giddiness, sadness, and awe, all rolled into one. (On that note, this is why I value exceptional audio. It breathes life into — and honors — superlative music. For me, in terms of emotional impact, no other art form comes close... and I say that having contentedly visited museums on four continents.)

When listening to the LS50W system on particularly dark-sounding records like Tom Waits' wonderful Orphans: Brawlers, Bawlers, and Bastards, I sometimes felt inclined to add a little top-end sparkle via Audirvana's on-screen equalizer — just a few dBs in the vicinity of 4000 to 5000 Hz. But that was rare, and only a mild preference rather than an urgent imperative.

In fact, on the scale between warm and analytical, the KEFs tip ever so slightly past the midway mark, but I have to emphasize that these speakers don't sound cold or "digital" — far from it. The Edifier S3000Pros I auditioned before the KEFs did exhibit a too-assertive top end, at least in my room; replacing them with the much more organic-sounding LS50Ws quickly brought relief, and yes, joy.

Next, I set up the KEF system in my larger, 450-square-feet listening room, on 26'' Perlesmith stands — and I became less smitten. The speakers occasionally had trouble "filling" the space, although to be fair, this depended on the kind of music I fed them. It wasn't the KEFs' capacity for sheer volume that was at issue; the company claims that they have a maximum output of 106dB, loud enough to dislodge the fillings from your teeth. Truthfully, the speakers still sounded immensely satisfying in the bigger room when reproducing relatively smooth and easy-going material: Donald Fagen's the Nightfly, Rickie Lee Jones' self-titled debut album, Roger and Brian Eno's Mixing Colors, etc. But busy, complicated arrangements by inventive pop artists like XTC or Frank Zappa, or thick, roiling metal swathed in the overtones of guitarists torturing their tubes — different story. The LS50Ws will render such material faithfully, but only if you settle for relatively polite volume levels. Turn the music up, way up, and you may find that the bass gets a bit anemic, and that both the midrange and treble take on a slightly glassy quality.

I can think of two reasons why my listening room might be the bigger culprit than the speakers. First, there's an open stairway about five feet behind my chair, leading to a second-floor landing with an interior volume of about 1,400 cubic feet (in addition to the 3,300 cubic feet of the main room). For a bookshelf/stand-mount speaker with a 5.25-inch driver, that's a lot of space to load with tight, convincing bass — a bit like asking an Oompa Loompa to deadlift an F-150. Second, I had the KEFs about six feet from the wall behind them. The ports on the rear of the enclosures are understandably better at workin' da bass when they're closer to a wall. When I moved the KEFs farther back, performance improved, but I still liked them best in a cozier space — to wit, in my 240-square-feet office, on my desk, just a hand's breadth from the back wall.

If I had to make an educated guess, I'd say that the speakers are likely to perform their magic in "closed" rooms of up to about 350, maybe 400 square feet. Beyond that size, if soft and gentle music isn't your thing, bigger drivers and enclosures are called for.

Daily Use And Ergonomics
As we've seen, the W in LS50W stands for wireless, but the system is anything but. Each speaker requires a power cord. A CAT cable, also supplied by KEF, must be strung between the two units to allow them to communicate. To get the most out of them, it's highly recommended that you establish an Ethernet connection to the main speaker — that's another cable, and we haven't even attached any sources yet. By the time you connect a computer, maybe a CD player, and (if desired) a subwoofer, you're looking at a serious cluster of spaghetti. This didn't bother me in the slightest, and I knew about it going in; but if you're drawn to the mighty little KEFs because of that tantalizing W, know that the letter means "Will work with Wi-Fi," not "WTF ma, no wires."

Turning the LS50Ws on and (especially) off can be moderately irksome. You get no tactile feedback from the small, smooth OLED display on the main speaker's top, where the power button resides along with controls for input selection and volume; you have to look and tap carefully on exactly the right area. When you turn the speakers off via the top control, there's a delay in response of about three seconds. The KEFs then chirp out their four-note "K bye" confirmation, and finally, after another second, the backlit controls go dark. Often, I touch that on-off control twice, either because the first press doesn't register, or because I'm simply too impatient. I realize this is akin to stupidly and unnecessarily mashing the call button to summon the elevator. Zenmasters and natural slowpokes should have no problem here.

But doesn't the LS50W system come with a remote control? Couldn't I just press the power button on that? Yes and yes. Let us now speak briefly of the KEF remote, and then never mention it again. I could perhaps forgive the company for making the wretched wand out of cheap-feeling plastic if it wasn't for the complete lack of ergonomics. The handfeel of the thing is preferable to gripping a cactus, but only just. Without carefully studying the surface, you can't tell which is the front and which the back, or even which side is up or down. This is greatly worsened by the color scheme. A slow-witted child would understand that dark red print on black plastic is barely legible even in broad daylight, let alone at night. It took me just an hour or two to decide to replace KEF's risible effort with a 10-dollar Chinese learning remote that, though ugly, at least lets me see and feel what I'm doing. After five minutes, I could operate it by touch. Problem solved.

To continue with my very brief enumeration of cons, the KEF streaming iOS app is as buggy as a fetid Louisiana swamp, with frequent dropouts and errors beyond anything I've experienced with other audio software. I've never heard my music slowed down drastically in tempo, but that's the effect I got more than once during just the first hour of using the app. I kid you not — several times, a song with, say, 120 beats per minute slowed down to 90 to 100 bpm for a few seconds. What on earth? I soon ditched the app and jumped back into Audirvana's familiar embrace.

Thankfully, KEF Control, the companion app that lets you pause, play, fast forward, etc, as well as tweak DSP/room-correction settings, worked without glitching, and so did streaming from the Tidal app.

Conclusion
I wish KEF nothing but the best. Still, because I love seeing affordable high-end audio soar to new heights, it's exhilarating to see competitors beating up the company (and each other!) with bad-ass powered/wireless speakers of their own. Kudos must go to the wonderfully voiced ELAC Navis ARB-51s ($2200 per pair), the too-bassy-for-me-but-still-winsome Devialet Phantom Golds ($5800), the sultry B&W Formations ($4000), and others.

Of these, the KEFs may just take the cake. Rubbish remote and silly streaming app aside, the company knocked it out of the park and into the stratosphere with the LS50Ws. And again — for a measly two grand? Holy hell! I'd consider the system a great value at twice, even three times that price!

Obviously, then, this is one prix-fixe feast I couldn't, and didn't, pass up.

Specifications
Type: Type: Active wireless loudspeaker system
Drivers: Tweeter: 1" vented aluminum dome; LF/MF driver: 5.25" magnesium/aluminum alloy
Frequency response: 45Hz to 28kHz (+/-3dB), measured at 85dB/W/m
Peak SPL: 106dB
Amplifier output power: LF/MF driver: 200W / Tweeter: 30W (per speaker)
Net: 2.4GHz / 5GHz dual-band Wi-Fi
Inputs: Bluetooth 4 with aptX, USB Type B, optical TosLink, and RCA analog line-level input
10/100 Mbps RJ45 Ethernet (for net and service)
Resolution: Up to 24 bit
Sampling rate: Up to 192kHz (USB)
Up to 96kHz (TosLink)
Power input: 100–240V, 50/60Hz
Dimensions: 11.8" x 7.9" x 12.1" (HxWxD)
Weight: Main speaker 22.5 lbs.; slave speaker 22 lbs.
Price: $1999.98

Company Information
KEF USA
10 Timber Lane
Marlboro, NJ 07746

Voice: (732) 683-2356
E-mail: info.us@kef.com
Web: https://us.kef.com