Review: KEF LSX Wireless


Mis à jour le 26 February 2019.

This week we reviewed the KEF LSX Wireless, the famous KEF LS50 Wireless’ smaller sibling. This active speaker fitted with a 4.5” (11.5 cm) UniQ driver is WiFi and Bluetooth aptX compatible. A CD player, a turntable with an integrated RIAA preamp, a UHD TV or a subwoofer may be directly connected to the KEF LSX Wireless.

KEF LSX Wireless: all-in-one concept

With the LSX Wireless, the manufacturer seems to have found a great recipe for success. The KEF LS50 speaker was lauded by the specialized press and by numerous listeners. We can only corroborate this opinion considering how much we loved the Marcel Wanders edition of the LS50. The KEF LSX Wireless doesn’t stray from the original concept and features a 4.5” (11.5 cm) UniQ driver –it’s older sibling was fitted with a 5” driver (13 cm)– and each speaker is powered by a bi-amplification system (70 W + 30 W). One of the two speakers features all of the inputs (Ethernet, digital optical, analog line-in) and outputs (RCA subwoofer).

The KEF LSX Wireless’ range of connectors is sufficient to connect both analog and digital sources. The USB Type A port allows the user to power a DAP for example.

KEF LSX Wireless: wireless, but only to a certain extent

Although the KEF LSX Wireless can connect to a WiFi network to stream audio files, Internet radio stations, and online music services, the master speaker and the slave speaker are connected together by a long, shielded Ethernet cable. This design was chosen to avoid any latency resulting from wireless transmission between the two speakers, especially when a TV or a Blu-ray player are also part of the equation. By doing so, KEF has avoided any audio-to-video synchronization issues. Moreover, the cable connection is not subject to RF interference. Nevertheless, 100% wireless connection is also possible with CD quality audio files (16-bits) and non HD streaming services.

Even though the KEF LSX Wireless speaker can be controlled more conveniently via its mobile app, KEF has still included a remote control.

KEF LSX Wireless: ideal amplification

By integrating two amplifiers in each speaker, KEF resolves the tricky issue of choosing an amp and speaker wires for the listener.

Better still, as each speaker is bi-amped, there are no passive filter components in the signal path, and therefore no deterioration. The active filter includes DSP tone and phase control, which can be adjusted by the listener through the KEF Control mobile app. Therefore, it’s possible to adjust the speaker’s sound signature. In advanced mode it’s possible to choose between three equalization settings for low frequencies, to adjust phase settings and even the cutoff frequency if the speakers are connected to a subwoofer. Even the tweeter’s sensitivity can be adjusted. The settings provided by KEF cover all the needs of demanding listeners. Perfect!

The KEF LSX Wireless boast a textile finish.

KEF LSX Wireless: UniQ driver

If you are not yet familiar with KEF’s UniQ speaker driver technology, know that it is based on the principle of the coaxial driver, in other words two speaker drivers in one. The tweeter is placed in the center of the mid-bass driver’s cone and is crowned with a phase plug. The KEF LSX Wireless is fitted with a 4.5” (11.5 cm) UniQ driver loaded in a bass-reflex enclosure with a back-firing circular port. Its frequency response is 50 Hz – 40 kHz, which is quite surprising considering how small this speaker is.

A LED on the front panel provides indications on the functioning status of the KEF LSX Wireless.

KEF LSX Wireless: testing conditions

We connected the KEF LSX Wireless speakers to our local network using an Ethernet cable. The speakers’ configuration is done through the dedicated KEF Connect app for iOS and Android. To connect the speakers to the WiFi network, simply follow the indications given by the app. Then, download the KEF Stream app to access the various music sources (Spotify, Tidal, DLNA or Roon server, audio files stored on a smartphone, Bluetooth connection, etc.). The speaker also comes with a remote control.

The KEF Control app allows you control the speaker, whereas the KEF Stream app lets you select the audio source. Note that a high-pass filter is included so as to let you connect a subwoofer to handle the low frequencies (and put less strain on the speaker’s amplifier).

KEF LSX Wireless: listening impressions

So, is the KEF LSX Wireless just a second rate version of the KEF LS50? Let’s be honest, it is actually quite the contrary. The KEF LSX Wireless are a lot cheaper than the LS50 Wireless and are only slightly behind in terms of performance. They are even livelier than the LS50. It goes without saying that the sound stage isn’t quite as wide, but the sound signature is the same. The mids are rich and punchy (without being harsh), the highs are well integrated and unobtrusive (adjustable level).

The lows have some serious oomph, sound just right, can sometimes go very low, and benefit from an exceptionally impressive dynamic range and articulation for a speaker this size. Many floorstanders are not able to deliver such a level of performance.

The LSX’s dynamic range quickly becomes addictive and we can’t help but turn the volume up to see if everything stays in place at high volume. Led Zeppelin’s rendition of Kashmir at the O2 Arena and La Grange by ZZ Top are breathtaking. The restitution is spacious, well layered, and extremely punchy.

Although the KEF LSX Wireless might look bright blue in some pictures, in reality it’s actually quite a soft hue.

We listened to FLAC files as well as Spotify (the Connect mode is very convenient) and we made sure to listen to different types of music (jazz, pop, classical musical). Never once did we feel even slightly frustrated.

KEF LSX Wireless: compared to…

KEF LS50 Wireless: The LS50 is fitted with a more powerful amplifier, better suited to its larger driver. Nevertheless, the sound signature is very similar. The smaller LSX, whose driver’s mobile parts are lighter, delivers more precise mids and tighter highs and lows. The LS50 Wireless delivers a wider and more commanding sound stage but the differences between the two speakers are minor.

Dali Callisto 2 C: The Dali speakers deliver more refined highs and boast a brighter sound signature, but are not as good as the LSX Wireless when it comes to dynamic range and cannot rival with the KEF’s scrupulous melodic restitution.

Dynaudio Xeo 2: A little more consensual, although very well balanced. No WiFi connection here, which means Bluetooth transmission and, as a result, a compressed and deteriorated signal.

KEF LSX Wireless: conclusion

It’s easy to fall head over heels for this active speaker, although their 1200€ price tag may seem a bit steep. But if you take into account the price of a system comprised of a good stereo amplifier, a DAC, a network player, and a very good pair of speakers, the KEF LSX Wireless is actually quite the bargain. Moreover, they are extremely compact and can be placed anywhere in the room considering the adjustment possibilities offered by the control app. Simply put, at this price point, we cannot recommend a better package. Everything is here: tones, transient response, dynamic range, coherent sound placement… The perfect recipe to immerse yourself in music for hours at end. On this note, we’re going back to our listening session.

The circular bass-reflex port at the back of each KEF LSX Wireless speaker.

What we liked:

  • The design and the blue tint
  • The sound restitution comparable to that of a fine-tuned high-end system
  • The placement possibilities
  • WiFi, FLAC, Spotify Connect, DLNA, Bluetooth aptX…
  • The gargantuan lows
  • The meticulous mids
  • The dynamic range, even at high volume
  • etc…

We would have liked:

  • We’re still looking for a drawback…


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