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KEF LSX Wireless Speaker Aims for LS50 Performance at 1/2 the Price

By Jacob Green
KEF LSX

KEF LSX

Summary

  • Product Name: LSX Wireless Speakers
  • Manufacturer: KEF
  • Review Date: January 30, 2019 00:00
  • MSRP: $1,100/pr
  • First Impression: Pretty Cool
  • Buy Now

Amplifier Output Power: 70 watts per woofer + 30 watts per tweeter

Frequency Response: 54Hz - 28kHz (±3dB)

Dimensions: 9.5 x 6.1 x 7.1 inches

Weight: 7.9 lbs/ 7.7 lbs

Executive Overview

KEF’s LS50 Wireless all-in-one speaker system has been hugely successful for the British loudspeaker manufacturer, and it recently took home the EISA (European Imaging and Sound Association) award for Best Wireless Loudspeaker of 2017-2018. For $2,200 per pair, the LS50 Wireless offers world-class sound from a compact package that includes a built-in network streamer, Bluetooth receiver, digital-to-analog converter, and amplifier. Now KEF is hoping to bring its wireless speaker concept to a wider audience with a miniaturized speaker system called the LSX. Like the LS50 Wireless, the LSX is a complete hi-fi system housed in two stylish bookshelf speakers. The speakers themselves are closer in size to KEF’s smaller X300A powered speakers from several years ago, but their performance and styling suggest that the LSX share a significant amount of DNA with the LS50 Wireless.

KEF LSX vs LS50W.jpg 


At $1,099 per pair, the LSX costs half as much as its bigger sibling, and its small size will appeal to style-conscious customers who don’t want an imposing loudspeaker dominating the room. Most users will connect to their home networks via the LSX’s dual-band 2.4GHz/5GHz wi-fi connection, though an ethernet input is also available. Once connected, the LSX can stream networked music via DLNA, or from Tidal, Spotify, or Roon. Support for Apple’s AirPlay2 protocol is coming in a firmware update expected to go out in January 2019, and AptX bluetooth makes it easy for friends to stream music from their phones and tablets. Wired connections include a 3.5mm analog aux input, and an optical digital input that can be used to connect a TV, game console, or disc player. Unlike the LS50 Wireless, the LSX lacks a USB input. The omission of the USB input is a bit of a disappointment; the LSX would make a fabulous pair of desktop computer speakers, and a direct USB connection is a simple solution that would allow a computer user to take advantage of the KEF speakers’ excellent built-in dac. Knowledgeable users can still make it work via wireless connectivity or the 3.5mm aux, but a USB input would have been welcome.

 KEF LSX white.jpg

 

KEF LSX vs LS Wireless Speakers

The LSX does include a subwoofer output, allowing the user to add both deeper bass and more potent dynamics, should the need arise. The subwoofer connection is configured via the KEF Control app for iOS and Android, which also allows the user to tailor the sound of the LSX to match its acoustical surroundings. For example, the app will ask whether the speakers are situated on a desk or on stands, if they’re near the rear wall or out in the open, and even whether the room is acoustically damped or lively. This information is filtered through KEF’s Music Integrity Engine, which the company defines as “a cutting-edge collection of bespoke Digital Signal Processing algorithms that ensure accurate time alignment and phase coherence.” It’s a lot of tech to pack into speakers that measure just 9.5 by 6.1 by 7.1 inches. The compact cabinets, designed with extensive Finite Element Analysis, employ constrained layer damping to help dissipate unwanted vibrations. Centered on the front baffle is a smaller version of KEF’s signature Uni-Q driver array. In the LSX, a 0.75-inch aluminum dome tweeter sits inside a 4.5-inch magnesium/aluminum alloy mid-woofer (downsized from 5.25 inches in the LS50 Wireless). In each speaker, the mid-woofer is powered by its own 70-watt class D amp, while the tweeter gets 30 watts of class D power. The larger LS50 Wireless uses class AB amps for the tweeters, and high-power 200-watt class D amps for the low end, but those amps take up more space and create more heat, necessitating the addition of bulky heatsinks. KEF has made inevitable compromises to reduce costs and the size of the LSX’s cabinets, which are made of plastic rather than the MDF used in the LS50 Wireless. But the LSX also has some new tricks up its sleeve — features you won’t find on the larger and more expensive LS50 Wireless.

Wireless Considerations

The LS50 Wireless requires that an ethernet cable be used to connect the left and right speakers. Serious audiophiles may not mind; to them, the LS50 Wireless represents a streamlined replacement for a stack of components and multiple cables. But it’s not hard to imagine that some customers might expect a speaker with the word “wireless” in its name to deliver on that promise in more ways than one. Then again problems with true wireles Hi-Fi stereo connectivity plagued the KEF MUO with syncing issues so they may have felt the need to steer clear of that dilemma.  The LS50 Wireless doesn’t need a wired connection to a source, but there’s no getting around that ethernet umbilical. In the LSX, it’s a different story. KEF has developed its proprietary, wireless inter-speaker connection. Each LSX speaker needs to be plugged into a wall socket, but that’s it. This proprietary wireless connection is limited to 24-bit/48kHz, which will be fine for folks upgrading from Sonos and other mass-market wireless speakers. Audiophiles with high-res aspirations can connect two LSX speakers with an ethernet cable, increasing the resolution of the inter-speaker connection to 24-bit/96kHz, while giving up some of the sleekness of a wireless setup. The choice is yours. (For the record, the LSX can play 24/192 files, but they’ll be down sampled to 24/48 or 24/96, depending on whether you’re using the wireless link or the ethernet cable to connect the speakers.)

Audiophile with Style

Another area in which the LSX excels is in visual style. Designed by the renowned industrial designer Michael Young, the LSX is available in five colors, four of which see the cabinet clad in an industrial fabric by Danish contemporary textile designer, Kvadrat. If you don’t like the fabric look, you can choose the gloss white option, which features a silver mid-woofer cone and red tweeter. Different color options feature different accent colors in the ports and tweeters, and a color-changing LED indicates which input is in use. These thoughtful touches, together with the LSX’s smaller size, will make KEF’s newest offering more visually appealing than its predecessor.

Will the LSX be another success for KEF? Can it deliver competitive performance at this lower price? Share your thoughts in the related forum thread below. 

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Recent Forum Posts:

KenM10759 posts on February 13, 2019 19:31
KEW, post: 1298265, member: 41838
How large of a room were you in? Was a sub connected?
Do you fell it had enough SPL to play in that room and normal (not loud, but room-filling) levels?

The room was the dealer's “lobby”, an area about 15 ft deep, 8-1/2 ft ceilings, about 10 ft to the left of the speakers open and about 18 ft to the right open. The LSX speakers were playing at “very loud speaking, not quite shouting” levels, perhaps 75-80dB. No problem filling that area and plenty more ‘gas in the tank.’ They truly sound SO much bigger than they are that's its nothing short of astonishing, at least to my ears.

I'd own them if the LS50's for $200 less hadn't come available just months before the LSX introduction.
KEW posts on February 13, 2019 09:04
gene, post: 1295271, member: 4348
KEF recently introduced their new LSX wireless speaker system. It offers some unique features, a more compact form factor and arguably better aesthetics over its bigger LS50 brother.


The LSX does include a subwoofer output, allowing the user to add both deeper bass and more potent dynamics, should the need arise. The subwoofer connection is configured via the KEF Control app for iOS and Android, which also allows the user to tailor the sound of the LSX to match its acoustical surroundings. For example, the app will ask whether the speakers are situated on a desk or on stands, if they’re near the rear wall or out in the open, and even whether the room is acoustically damped or lively. This information is filtered through KEF’s Music Integrity Engine, which the company defines as “a cutting-edge collection of bespoke Digital Signal Processing algorithms that ensure accurate time alignment and phase coherence.”

It’s a lot of tech to pack into speakers that measure just 9.5 by 6.1 by 7.1 inches. The compact cabinets, designed with extensive Finite Element Analysis, employ constrained layer damping to help dissipate unwanted vibrations. Centered on the front baffle is a smaller version of KEF’s signature Uni-Q driver array. In the LSX, a 0.75-inch aluminum dome tweeter sits inside a 4.5-inch magnesium/aluminum alloy mid-woofer (downsized from 5.25 inches in the LS50 Wireless). In each speaker, the mid-woofer is powered by its own 70-watt class D amp, while the tweeter gets 30 watts of class D power. The larger LS50 Wireless uses class AB amps for the tweeters, and high-power 200-watt class D amps for the low end, but those amps take up more space and create more heat, necessitating the addition of bulky heatsinks. KEF has made inevitable compromises to reduce costs and the size of the LSX’s cabinets, which are made of plastic rather than the MDF used in the LS50 Wireless.

But the LSX also has some new tricks up its sleeve — features you won’t find on the larger and more expensive LS50 Wireless.

28048
KEF LSX (left) vs LS50 (right)

Read: KEF LSX Wireless Speaker Preview to find out more.


The article says:
KEF LSX vs LS Wireless Speakers

The LSX does include a subwoofer output, allowing the user to add both deeper bass and more potent dynamics, should the need arise. The subwoofer connection is configured via the KEF Control app for iOS and Android, which also allows the user to tailor the sound of the LSX to match its acoustical surroundings. For example, the app will ask whether the speakers are situated on a desk or on stands, if they’re near the rear wall or out in the open, and even whether the room is acoustically damped or lively. This information is filtered through KEF’s Music Integrity Engine, which the company defines as “a cutting-edge collection of bespoke Digital Signal Processing algorithms that ensure accurate time alignment and phase coherence.”

The comment on the subwoofer connection being “configured through the app” is pretty vague for such an important aspect of this speaker!
For a small speaker like this, I would consider the application of a crossover (with high pass filter for the mains) to be extremely valuable in freeing these speakers to focus on higher frequencies where it can put out some strong SPL!
Given app control and DSP, it seems a no-brainer that this should have a proper application of a HPF for the mains, but I did not see it addressed!
Does it?
Thanks!
KEW posts on February 13, 2019 08:56
KenM10759, post: 1295580, member: 76547
I had the opportunity to audition the LSX speakers on the day they were released, though I'd heard about them and seen photos well before the official date. Owning LS50's (not the LS50 Wireless), I must say I was very surprised at just how close in overall performance to those that the LSX actually sounds.

I also don't know if port plugs are included but would be shocked if they weren't supplied. Even so, the DSP affords quite a good way of tailoring the output for nearly every placement situation. These LSX are shocking in how much sound they put out for their diminutive size! And I think the textile finish looks much better in person than any photos I've seen. One small, odd detail is that only the green color ones carry the Michael Young (designer) signature on the front baffle.
How large of a room were you in? Was a sub connected?
Do you fell it had enough SPL to play in that room and normal (not loud, but room-filling) levels?
Sheep posts on February 11, 2019 10:53
It seems like a lot of these powered desktop speakers with subwoofer outs don't put any High Pass filters in place when a sub is used (or without). I was trying out some Kanto YU2 speakers and the little 3 inch woofers were wasting a lot of time and energy trying to play notes below their ~70Hz limit. I swapped those out for a Kanto Yaro amp and some Energy C-50s that I had laying around. Paired those with my spare Velodyne Deco 8 subwoofer and my PC system can take on pretty much anything I can throw at it.

SheepStar
shadyJ posts on February 09, 2019 15:33
KEW, post: 1297193, member: 41838
Thanks for that!
I obviously had a totally wrong conceptual model of how the port influenced the driver's behavior!
Ports use resonance - Duh! I should have thought it through a little better! I was just thinking of the pressure in the box during a large excursion as restricting the driver and limiting the bass.
However, you are looking at it from the perspective of getting the same bass out of the speaker. When we are plugging the port (without attempting to recapture the SPL) aren't we reducing the travel (unless it had a positional servo)?
If you simply plug the port on a passive design, you do increase the back pressure on the driver a little bit above the port's native tuning frequency, and a lot below the port's native tuning frequency. However, that doesn't mean it can't be overdriven. There needs to be filters in place to avoid over-driving these things. Simply sealing them is not enough to protect them.
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