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KEF LSX Review (Wireless Speaker)

amirm

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This is a review and detailed measurements of the KEF LSX "Wireless" speaker. It is on kind loan from a member and costs US $1,250 from Amazon including Prime shipping.

In every way KEF could nail the look and feel of the speaker, it has done so:

KEF LSX Review Wireless Powered Speakers.jpg


Not only is the iconic coaxial driver there, the whole speaker is now wrapped in nice fabric which you can see better in this picture:

KEF LSX Review back panel Wireless Powered Speakers.jpg


Check out the accent color even on the port which normally would not be seen! Absolutely great.

What is not so great is if you get the speaker without the hard remote and you want to use the Aux in analog input. Upon power up, it would not play anything from that input. A dancing sequence of colors were going on in the front which would require the German Enigma machine to decode. I figured the easiest thing is to plug an Ethernet cable into it so I didn't have to mess with configuring WiFi. Searched for KEF and the KEF Connect app came up. Strangely it said it was from "GP Acoustics." Had to do some searching to see that is the entity that owns KEF now. But why reduce consumer trust by using that name instead of KEF???

Anyway, I start the app and it says to register. :( I register and then it comes up asking me if I want it to search for speakers. I say yes and the app simply hangs forever. :( I try it and try it again to no avail. I see a reset button on the back. I push that it and nothing resets either. What the heck? Sometime later I discover that the hole below Reset market is an LED! The switch is below it. What is remarkable is that you need to reset the speaker if you want to go from Bluetooth to Wifi mode. So why, oh why, is it not a real switch? And why require a reboot for heaven's sake to switch between those two protocols?

Back to trying to figure out why I can't connect, the app says to open "Google Home" if it can't find the speaker. Google Home? I knew there was such a thing on iOS but not on Android. I find and start it. An app opens up that seems to have been written by an intern developer. On top it says something about "IOT" (Internet of Things) exception that it has printf formatting characters in it with back slashes and such. Desperate, I tell it to search for them. To my pleasant surprise it says it found the device and gives me some cryptic designation for it. I say fine.

To test, I bring up Google Music (or whatever it is called) and start to play a track. I hear music! Yeah.... But wait, why is the volume so low? I crank it up and mostly I hear bass. It was just then that I realized the sound was NOT coming out of KEF LSX but elsewhere in the house!!! I immediately hit pause go to the living room. I see my wife in near tears as the Pioneer AVR that we use for TV sound had switched to be a remote device for Google Home and started to play the bloody music at full volume! Had to spend 10 minutes calming my wife's nerves. Shut the whole thing down and left it there for a couple of days.

I came back to it and searched and searched and nothing online would talk about this problem. By accident I watch a KEF configuration video and it shows a different app than the one I used. It is called KEF Control, not Connect! I boot that up and it immediately makes progress past where I was stuck with the other app. Sadly it configures itself using ad-hoc WiFi access point in the speaker. So you need to connect to its network first, give it your real WiFi credentials and then it connects. It should do this with Bluetooth in this day and age. Anyway, once there, I managed to select Aux In and could test the speaker.

Online reports are full complaints about the App with the most serious one being that it doesn't remember its settings. Horrible job here by KEF.

Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field") which sharply reduces the impact of room noise. Both of these factors enable testing in ordinary rooms yet results that can be more accurate than an anechoic chamber. In a nutshell, the measurements show the actual sound coming out of the speaker independent of the room.

I performed over 1000 measurement which resulted in error rate of 1 to 2%.

Reference axis was the tweeter center.

KEF LSX Measurements
Acoustic measurements can be grouped in a way that can be perceptually analyzed to determine how good a speaker is and how it can be used in a room. This so called spinorama shows us just about everything we need to know about the speaker with respect to tonality and some flaws:

KEF LSX Frequency Response Measurements Wireless Powered Speakers.png


Ignoring a few kinks, this is a very reasonable on-axis frequency response. There is a strange drop post 8 kHz and a glitch around 800 Hz. We can see the cause of both in our near-field measurements:

KEF LSX driver Frequency Response Measurements Wireless Powered Speakers.png


We see that a resonant tone is coming out of the port around 800 Hz and interfering with the woofer response. We also see quite an uneven response from the tweeter. it is worse than our spin graph though so this may be partially due to artifacts of measuring the tweeter at very close distance (comb filtering from the face of the microphone and woofer).

Directivity is very good which is why the early window response is reasonable:
KEF LSX Early Window Frequency Response Measurements Wireless Powered Speakers.png


Combined we have a very good predicted in-room response:

KEF LSX Predicted In-room Frequency Response Measurements Wireless Powered Speakers.png


The best news is dispersion. Check out the beam width in horizontal axis:

KEF LSX Horizontal Beamwidth Measurements Wireless Powered Speakers.png


I think the last time we saw something this good was on a Genelec with coaxial driver. Very nice.

This is reflected just the same in our contour plot:

KEF LSX Horizontal Directivity Measurements Wireless Powered Speakers.png


Being coaxial, the vertical contour looks almost as good:

KEF LSX Vertical Directivity Measurements Wireless Powered Speakers.png


What this means is that the speaker tonality will not change much if you sit above or below tweeter axis. Or slide to left or right. It will also be room friendly as reflections have similar tonality to on-axis response.

Distortion at 86 dBSPL is reasonable. Not so at 96 dBSPL:

KEF LSX THDpercentage distortion vs Frequency Response Measurements Wireless Powered Speakers.png


KEF LSX THD distortion vs Frequency Response Measurements Wireless Powered Speakers.png


I could hear massive distortion in low frequencies as the sweep was running in the lab. This is typical of many small powered speakers as I think the amp is running out of power, not the driver.

KEF LSX Listening Tests
I chose to test these speakers in near-field since many will buy them to use on their computer desk and such. It took just a few seconds to realize the tonality was correct. Listening spot was wide and I could detect very little change as I moved left and right, and sat taller and lower. Track after track sounded excellent, obviating the need for any equalization in my setup (for the speaker that is, the room you still need to EQ).

Throwing sub-bass heavy tracks to LSX created no drama. It simply attenuated them heavily and went about its business. I much rather have this that a driver bottoming out and cracking as many speakers do.

Conclusions
The KEF LSX is not quite technically perfect but comes pretty close. It is wrapped in super attractive packaging making for a very nice combination. It is expensive for the fidelity you get but studio monitors that do as well are very ugly and industrial compared to LSX.

I am happy to put the KEF LSX on my recommended list. I hope they improve their App and documentation though. I hate them for that. :)

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As always, questions, comments, recommendations, etc. are welcome.

Appreciate any donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

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Somafunk

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I see my wife in near tears as the Pioneer AVR that we use for TV sound had switched to be a remote device for Google Home and started to play the bloody music at full volume! Had to spend 10 minutes calming my wife's nerves.

:facepalm:
 

Anmol

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How does it compare sound wise to q350, obviously not wireless? I see higher preference rating for q350 but not recomended but this at double the price is recomended with lower preference rating?
 

VintageFlanker

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Thanks, @amirm

This is confirming measurements from @John Atkinson: exceptional performance for such a small box, except for high SPL...

Still, 54Hz at -3.8dB is quite an accomplishment from a single 11.5cm coax driver.:cool:
I see higher preference rating for q350 but not recomended but this at double the price is recomended with lower preference rating?
Apples and Oranges: first, Amir recommandations are not directly related to Olive's Score. Second, it costs twice the price since this is an entire system (including DAC, DSP, amp and streamer) in a very compact design.
 
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MediumRare

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With the greatest respect, there’s no way this should get a champion Panther. I tried them at an audio store and they were dull and muddy. I’m guessing it was both the roll off above 8k (I hear only to 14k) and the distortion when played loud. They were so disappointing.
 

MZKM

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Apples and Oranges: first, Amir recommandations are not directly related to Olive's Score. Second, it costs twice the price since this is an entire system (including DAC, amp and streamer).
Plus I think Amir tested that as a regular speaker and this as a desktop/computer speaker. Besides the resonances of the Q350, it seems Amir didn't like the narrow horizontal soundstage of the Q350; may be worthwhile to test the LSX as a regular speaker and see if he feels the same.

That said, the LSX has noticeably wider horizontal dispersion than the Q350, maybe due to using a 0.75" tweeter,

It's still using my old scaling, but here is the Q350:
index.php


And the LSX:
index.php


The LSX doesn't even go past -20dB. Plus it becomes more omni higher in frequency (~200Hz vs ~120Hz), so that likely helps as well.
 
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Anmol

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Plus I think Amir tested that as a regular speaker and this as a desktop/computer speaker. Besides the resonances of the Q350, it seems Amir didn't like the narrow horizontal soundstage of the Q350; may be worthwhile to test the LSX as a regular speaker and see if he feels the same.

That said, the LSX has noticeably wider horizontal dispersion than the Q350, maybe due to using a 0.75" tweeter,

It's still using my old scaling, but here is the Q350:
index.php


And the LSX:
index.php


The LSX doesn't even go past -20dB. Plus it becomes more omni higher in frequency (~200Hz vs ~120Hz), so that likely helps as well.
while i do understand value proposition due to number of features/functions included but primarily a speaker needs to sound good. didn't sound good to me at all so everything else became irrelevant. if olive score is not a correlated to Amir's recommendation then thats fine, nothing to comment upon - different strokes for different folks. thanks
 

wwenze

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hrowing sub-bass heavy tracks to LSX created no drama. It simply attenuated them heavily and went about its business. I much rather have this that a driver bottoming out and cracking as many speakers do.

Looks like dynamic range compression in the bass, looking at the 86dB vs 96dB graphs

86dB graph FR looks flat all the way down to 100Hz. That's nice.

BTW I notice the 86dB / 96dB graphs have wriggles in the bass while the spinoramas don't. Are those measured differently from spinorama?
 

Ata

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Thank you @amirm ! Looking forward to reviews of other KEF speakers, particularly LS50 Meta and Wireless2.
 

phoenixsong

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Poor wife, that must have been terrifying :oops:

I've listened to this speakers in a shop with my recruit before, at near-field with the wall not too far behind them they have really nice spatial cues and beefed-up bass
 
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amirm

amirm

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BTW I notice the 86dB / 96dB graphs have wriggles in the bass while the spinoramas don't. Are those measured differently from spinorama?
Yes, they are in-room measurements. I can make them anechoic but it is extra work and doesn't change the message much.
 
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amirm

amirm

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Thank you @amirm ! Looking forward to reviews of other KEF speakers, particularly LS50 Meta and Wireless2.
More KEFs are here to be tested. :)
 

Kachda

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Damn. Was thinking of getting this from ebay, prices are going to shoot to as fellow asr members bid up prices :)
 

brandall10

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Damn. Was thinking of getting this from ebay, prices are going to shoot to as fellow asr members bid up prices :)

FWIW, the LSX II is rumored to drop sometime this summer... would def wait if you want a deal on this version or the latest and greatest.
 

brandall10

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With the greatest respect, there’s no way this should get a champion Panther. I tried them at an audio store and they were dull and muddy. I’m guessing it was both the roll off above 8k (I hear only to 14k) and the distortion when played loud. They were so disappointing.

As an owner of Buchardt A500s in my living room and a set of LSX for my bedroom, I find these to be pretty competent, though I'm surprised they performed this well. I can't imagine them sounding all that good in a larger space though (my bedroom is about 900 cubic feet).
 
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brandall10

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Only if they plan to use this wireless speaker non-wirelessly. Can they do that?

What does this mean? It should have no qualitative impact. They do have digital inputs as shown in the photo above.
 
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