KEF LS50 Wireless II review

Few hi-fi speakers have received as much coverage in the last ten or twelve years as the KEF LS50 and the family of KEF wireless speakers derived from it. With the current second generation of the LS50 Wireless, KEF has reached a high level of maturity and an impressive sound level. Much has already been said and written about this. But LowBeats has now listened to the KEF LS50 Wireless II and the brand-new KC62 mini subwoofer. The result inspires. But two little things should be improved…

First Straight to the Conclusion

Serious question: Which HiFi fan and LowBeatsReader is unfamiliar with the KEF LS50 loudspeaker series? … No one raises their hand? I am not surprised. However, let me briefly recap. The triumph of the small speakers with a strongly rounded front and KEF’s coaxial “Uni-Q” driver began in 2012. KEF presented the speaker as an anniversary model for the company’s 50th anniversary, but at the time, they could not have guessed that it would be one of the most popular passive speakers and have created mega sellers of the high-fidelity modern age. The concept: Compact dimensions, extremely low-resonance housing, and a single coax driver per box as a quasi-point sound source. And all this for a reasonable price of around 1,000 euros per pair. With its extremely precise, spatial, and highly audiophile sound, the LS50 quickly became the favorite of the HiFi feuilleton.

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Logically, KEF had to refine this recipe further for success at some point, which they only realized in the form of the active LS50 wireless version in 2017. A year later, the KEF LSX was added, which doesn’t have the same name but can be seen as a shrunken version of the LS50.

A technically advanced passive version of the LS50 only appeared in September 2020 with the “Meta”. Together with the LS50 Wireless II, KEF introduced, among other things, an ingenious component that is also found in the active version described here. More on that later.

KEF also celebrated great success with the public with the first LS50 Wireless. These speakers could be described as the archetype for affordable all-in-one streaming speakers that also meet higher sound demands. Completely different from the one-box solutions with streaming function that have been the most common to date.

But the LS50 Wireless of the first generation also had its pitfalls. Dropouts due to connection problems, somewhat sluggish and sometimes cumbersome operation, the rudimentary app, limited support for streaming services, and other small things were among the inconsistencies that users had to come to terms with.

Of course, the question of whether KEF was able to eliminate these stumbling blocks in the LS50 Wireless II is all the more exciting. In addition, below, we look at how well the recently introduced KEF KC62 mini subwoofer fits the LS50 Wireless II.

LS50 Wireless II: Well-matured and in fresh (matte) colors

The basic concept of the LS50 WII remains unchanged. Two fully active loudspeakers with digital signal processing form a stereo system consisting of a “master” and “slave”. Online streaming services are supported as sources, as well as streaming in the local network and locally connected components such as TV, CD player, etc. Each of the two loudspeakers has two amplifiers (separately for bass/midrange and treble) with a total output of 380 watts per box.

KEF has listed the numerous differences to its predecessor in great detail on its product page, which is why I would only like to go into some of the most important points here. So there is finally a uniform app – KEF Connect – for connection and operation. The range of online streaming services has been massively expanded. While Tidal, Spotify, and QQ Music are the predecessors, there are now ten services to choose from for the new ones within the app. This includes podcasts and, surprisingly, Apple Music. In addition, the Wireless II has recently become Roon Ready. There are other streaming options via UPnP, Chromecast, and Apple AirPlay 2, as well as via a Bluetooth direct connection. Multiroom support is now also available.

Other important innovations are support for PCM sampling rates up to 384kHz/24bit and DSD256. A maximum of 192 kHz PCM can be used natively. This requires a cable connection between the master and the slave. If the music is transmitted wirelessly to the slave (also new), the limit is 96 kHz. The speakers also master the “end-to-end protocol” MQA.

The 12th generation Uni-Q is now used as the driver. They are mainly characterized by the use of a technique called metamaterial absorption technology (MAT). A relatively flat, round disc is used behind the driver, with a kind of labyrinth milled into the inward side. The mathematically calculated corridors of the labyrinth that can be seen on it all have different lengths and branches, the purpose of which is to absorb different frequency ranges as best as possible and thus eliminate the sound components of the tweeter radiated from the rear. A film made by KEF tries to explain the concept.

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On the outside, not much has changed at first glance – apart from the newly offered color variants with a matte finish. The evolution is most likely to find visible expression on the back. For example, there is no USB connection. This is redundant insofar as network-capable loudspeakers such as the KEF LS50 WII can also be loaded with music from any computer via LAN or WLAN.

Instead, KEF donates an HDMI eARC port for connection to the television. This not only transmits the sound but also on and off commands from the TV. The volume can also be controlled using the TV remote control. Provided the TV supports HDMI CEC (Consumer Electronics Control), the cable is suitable, and the HDMI input is selected. When using the other inputs, the level control and on/off must be carried out via the IR remote or the KEF app.

Subwoofer KEF KC62: So small and already with the stormtroopers?

Subwoofers are by no means a new invention. Incidentally, the first active bass cubes of this type came from the Danish – at that time still US-American – manufacturer M&K (Miller & Kreisel) in the early 1970s. Today, almost every loudspeaker manufacturer has a subwoofer solution in its range. Some companies have even specialized entirely in this type of product, such as Velodyne or SVS. Most of the time, these are more or less cube-shaped boxes, mostly of a fairly bulky nature. The reason is simple: Without special measures, small membranes are only suitable to a limited extent for potent (low) bass performance.

If you want to add a subwoofer to a small room with limited space, you don’t have many options. This is because finding very small subwoofers that still deliver good bass is hard. The Velodyne MicroVee is one of the few exceptions—it’s small and performs well, but its bass capabilities are limited, especially below 45 Hz.

Now, KEF has introduced the KC62, a compact active subwoofer about the same size as the MicroVee. However, the KC62 claims to reach an impressively low frequency of 11 Hz, which is much deeper than what the MicroVee can handle. This makes it a great option for small spaces where you still want powerful, deep bass.

To achieve this, KEF has developed a completely new and very innovative dual driver system: Uni-Core. At first glance, these are two woofers mounted back-to-back according to the force-cancelling principle, which is also used in the KEF Blade, for example. The drivers support each other, which, among other things, reduces the transfer of kinetic energy to the housing. At second glance, however, it becomes clear: something is different here.

The patent-pending uni-core “double whopper” uses only a single magnet system shared by both diaphragms with two magnetic gaps and concentrically arranged, overlapping voice coils. This allows the drivers to move closer together but still produce a large cone excursion. For this to work, KEF had to dig deep into its bag of tricks.

One of the biggest challenges in the design was to adapt the behavior of both drivers to each other. The different-sized voice coils and their overlapping working areas result in mechanical and electrical differences. But both membranes must behave the same. KEF has described its measures in detail in this white paper (PDF, English).

The Uni-Core works in the KC62 in a closed housing. Flow noises through reflex openings are thus already excluded. To ensure that there are no other disturbing noises with the necessary large cone deflections, KEF has also developed a new surround called P-Flex. Their unusual structure is based on the origami paper folding technique. The purpose of the exercise is that the beading material produces less inherent noise when deformed and, above all, can better withstand the enormous air pressure that occurs inside the housing. KEF also explained this complex development in detail in the white paper.

Further measures to achieve the squaring of the circle: “Smart Distortion Control”. This is a hybrid system that combines DSP pre-correction with indirect detection of cone movement and feedback and is said to have a very significant share in the performance of the KC62. All this sits in a compact, extremely stable housing made of die-cast aluminum and weighs an impressive 14 kg. Anyone who lifts the approximately football-sized woofer will be amazed. And as it turns out, KEF has created a real magic cube with the KW62.

The KEF LS50 WII + KEF KC62 in practice – lots of sun, only a few clouds

The LS50 Wireless II clearly shows the experience that KEF has gained with its predecessors. This makes setup very easy with the new, unified KEF Connect app. Set up the speakers (if possible on good stands), connect the power cable, and follow the instructions in the app. In the factory setting, the master and slave automatically connect wirelessly. The wired mode can be activated in the app’s settings, which I recommend. Because in the test, the slave occasionally lost the connection during the radio connection and fell silent for a few seconds. Not often, but every failure is one too many. In addition, it always takes a few seconds after the system is switched on before the slave also starts up.

When connecting to the home WLAN, there was a problem at first. The app kept losing contact with the speakers. After I switched the WiFi pairing from 5 to 2.4 GHz band, this problem did not occur again. If you like and don’t shy away from an additional cable, you can also use a LAN cable to establish the network connection from the router to the master. This is still the most reliable method.

The Connect app offers a clear home screen that offers quick access to inputs, music services, and radio stations/podcasts. Important basic functions can also be controlled via the supplied but somewhat simple IR remote control and sensor buttons on the top of the master speaker.

Sometimes, I miss a display that informs me about the set volume. Also, source switching via the IR remote is often a guessing game. without looking down at the master speaker, where a few touch controls and displays can be found since the inputs can only be switched through one at a time and not directly selected. It’s also a pity that web radio cannot be started/stopped using the play/pause button on the remote control. Workaround when the phone rings: press mute.

Integrated online services such as Qobuz or Spotify can be operated within the Connect App. Although this does not offer the complete comfort of the original apps, it works very well in practice. As usual, the speakers can be selected as an output device via Roon, and the music can then be operated from here. The Connect app is then only needed occasionally if a setting needs to be changed. For example, if a subwoofer is to be connected.

Here are a few more screenshots from the app:

Subwoofer connection and setup via Connect app

Here, too, there are two types of connection to choose from: Via cinch cable from the LFE-Out on the master to the LFE-In on the subwoofer or via radio. The latter, however, is only optional via the KW1 adapter, which costs 200 euros.

Since version 1.6 (which was released with perfect timing shortly after the test devices arrived), the software has presets for various KEF subwoofers – including, of course, the KC62. This makes the setup very easy because the crossover frequencies are already specified here. The KC62 is only coupled at a low 45 Hz (low pass). The main speakers, on the other hand, slowly fade out at 70 Hz (high pass). The gap between 45 and 75 Hz is, of course, well thought out. Due to the edge steepness of the filters, the frequencies overlap, which leads to a balanced overall response. Of course, the preset settings can also be changed depending on the living room acoustics, installation, and taste. The preset then no longer says “KEF KC62” but “Custom”.

The fact that the KC62 subwoofer can produce such deep bass (even at frequencies where the Velodyne MicroVee struggles) is a smart design choice. This allows the small subwoofer to be placed almost anywhere in the room, giving you more flexibility when deciding where to put it. To adjust for different placements, you just need to set the “EQ” switch on the back of the subwoofer. For example, you can choose “Wall” if it’s near a wall, “Corner” if it’s in a corner, and so on. For the correct volume level, the knob should be set to exactly three o’clock.

In a second test, I connected the KC62 to my desktop setup, which includes the Wilson Audio TuneTot speakers and the Lyngdorf TDAI-1120 amplifier using its LFE output. The Lyngdorf’s “RoomPerfect” calibration system helped fine-tune the sound. The KC62 was placed discreetly behind my monitor on the windowsill, almost completely hidden. This is where its small size shines—larger subwoofers simply wouldn’t fit in my desktop setup. The KC62’s compact design makes it perfect for small spaces like this.

It all works great and sounds fantastic (see below), but unfortunately, there are two criticisms of the KC62. First: The automatic signal detection is a bit too insensitive in my opinion, especially when used together with the KEF LS50 Wireless II. The subwoofer found it difficult to start at very low levels; only with a somewhat louder (or very deep) tone did he start his work. In my listening situation, that’s a bit unfortunate because I sometimes listen very quietly and because the main speakers are high-pass filtered at 70 Hz with the KC62 preset, even without the sub switched on. After 20 minutes without a signal – or too low a signal – the KC62 switches to standby. The user has to turn the volume up briefly to reactivate the deep bass fundament.

Secondly. Like many of its subwoofer competitors, the KEF KC62 hums a bit. Quiet, but audible during breaks in music. At first, I thought there was a fan running in the case, but of course, there wasn’t. To completely rule out the LFE line as the cause, I ordered the ” KW1 Wireless Subwoofer Adapter Kit “. This consists of a transmitter that connects to the LFE output of the LS50 master speaker (or other device with an LFE out) and a receiver box with a dedicated four-pin connector for compatible KEF subwoofers, which include the KC62. Result: It hums even a bit more without the LFE cable. But ultimately, this point is academic because when music is playing, the hum is inaudible.

Best practice recommendations for the KEF LS50 Wireless II with KC62

1. For an optimally focused sound, set up the speakers as freely as possible and in an exact stereo triangle on stable feet. Matching ones from KEF cost 449 euros and can be filled with quartz sand, lead shot or similar if required.

2. Angle the loudspeakers toward the listening position so that the sides of the housing pointing inward are just visible.

3. The 2.4 GHz network is usually more reliable for WLAN.

4. Connect the slave to the master with a cable.

5. Use a well-shielded cinch cable for the LFE connection.

6. Set up the subwoofer in the area of ​​the main loudspeakers if possible.

7. Connect all components of the chain to a common power strip. Especially with active loudspeakers, different wall sockets are often used because of the installation, which, in the worst case, can lead to ground loops.

8. Bluetooth or AirPlay are only second-best choices for sonically demanding listening….

Soundcheck: The KEF LS50 never sounded so great

I don’t need to say many words about the musical capabilities of the LS50 Wireless. Only this much: The fantastic three-dimensionality and imaging precision for which they are so famous is, of course, fully retained in the latest version. Thanks to the higher system performance and the optimizations in the high-frequency range using metamaterial, the Wireless II appears even more dynamic, more responsive, and much finer at the top. But maybe also a bit reserved. With plus 0.75 decibels “Treble Trim” (adjustable in the app), I liked the image in my listening room best.

Combined with the KC62, the KEF LS50 Wireless II once again surpasses itself. Assuming the speakers are properly positioned and the subwoofer level is adjusted, it is hard to believe that you are dealing with such a compact set. In my roughly 20 m² small listening room, the KC62 inspires with unbelievable depth and cleanliness that I would never have expected from a sub with such a long excursion and such a small chassis. The KC62 is just as pleasing with music as with (not too extreme) home cinema use with crashing explosions, rumbling avalanches, and hurricane-like storm noises.

The connection to the LS50 WII via the preset in the Connect app works almost perfectly in my room. However, since there is no calibration function for the room acoustics for either the speakers or the sub, I only miss a better balance compared to the results of room correction systems such as the fantastic Trinnov Amethyst. This is simply due to the room’s acoustics. It would be the next logical step for KEF to develop an adequate room correction solution for its DSP loudspeakers.

But, and this is the most important thing: it is always a pleasure to see how tangible and detailed the LS50 WII fans out what is happening between the loudspeakers. There is little competition in this class. Even the recently tested Q Active 200 cannot keep up. Together with the KC62, the necessary sovereignty of the performance is added to experience an extremely lifelike concert feeling in small to medium-sized rooms or acoustically immersive films/series like never before. The KEF LS50 Wireless II with KC62 should be an eye-opening experience for many HiFi climbers.

Conclusion – The Premier League of All-In-One Speakers

2,500 euros is no small matter. If you add the feet and the KC62 subwoofer, we even get around 4,500 euros. And yet I consider the package to be cheap. If you consider that this sum includes a complete high-end entry-level system with a large range of functions and a versatile streaming solution with a comparatively small footprint, the sum is put into perspective.

All-in-one solutions like this are the ideal way for all those who just want to achieve good sound without experimenting with large equipment parks. The KEF LS50 Wireless II with KC62 undoubtedly represents a top-of-the-line solution in this segment. The KC62 subwoofer deserves extra credit for delivering insanely good bass performance from such a small package.

If you can come to terms with the special features mentioned in the text about cabling, the KEF LS50 Wireless II convinces with a high degree of maturity and high comfort. On the other hand, KEF could still make some adjustments to the KC62. Fortunately, its slight tendency to hum when idling and the automatic switch-on, which is a bit too insensitive in some situations, do not affect the actual sound. And so the bottom line remains: the KEF LS50 Wireless II sound excellent, as expected. But if you also have the sub activated, it will be great.

Addendum 05/31/21: The associated Connect app is now available in version 1.7 for iOS and Android in German. In addition to improvements in HDMI-eARC compatibility, the transfer of individual sound profiles via the cloud within the KEF Connect user account is now possible for the first time across devices and operating systems. This should make it particularly easy to transfer sound profiles that have already been created from one device to another.