KEF LSX Wireless Speaker Targets LS50 Performance

gene

gene

Audioholics Master Chief
Administrator
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.

kef.jpg

KEF LSX (left) vs LS50 (right)

Read: KEF LSX Wireless Speaker Preview to find out more.
 
hk2000

hk2000

Junior Audioholic
Compact powered speaker designers need to take into account that if you're providing a subwoofer output, you need to design the speaker for sealed operation and provide a port plug to be used when a sub is connected, better yet, make it sealed in the first place. I don't know why those designers can't take that into account. NHT and, recently, Fluance, got it right- you design a compact powered speaker with a subwoofer output, there is no need for a fart port!
 
John Parks

John Parks

Full Audioholic
Compact powered speaker designers need to take into account that if you're providing a subwoofer output, you need to design the speaker for sealed operation and provide a port plug to be used when a sub is connected, better yet, make it sealed in the first place. I don't know why those designers can't take that into account. NHT and, recently, Fluance, got it right- you design a compact powered speaker with a subwoofer output, there is no need for a fart port!
I saw your comment to the same effect n the Sound and Vision website!

I am sure the engineers who designed the LSX certainly took the function with a subwoofer hooked up into careful consideration. I listened to the LSX with and without a subwoofer and it is an incredible (and excellent sounding) piece of engineering. KEF provides port plugs for mist of their ported designs - I would be surprised if this was not the case.
 
KenM10759

KenM10759

Audioholic Samurai
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.
 
Sheep

Sheep

Audioholic Warlord
Compact powered speaker designers need to take into account that if you're providing a subwoofer output, you need to design the speaker for sealed operation and provide a port plug to be used when a sub is connected, better yet, make it sealed in the first place. I don't know why those designers can't take that into account. NHT and, recently, Fluance, got it right- you design a compact powered speaker with a subwoofer output, there is no need for a fart port!
I would rather have the port so the low end is better when there isn't a subwoofer. What I WOULD like to see is a high pass filter applied when a subwoofer is used so the little speakers don't try to handle frequencies that the subwoofer will take on.

SheepStar
 
S

shadyJ

Speaker of the House
The LSX should absolutely be run in a ported configuration. It's 4.5" midwoofer will run out of excursion real fast if it is tasked to play any bass at all. And it has even less surface area than a regular woofer since a chunk of its cone real estate is taken up by a tweetert.
 
KenM10759

KenM10759

Audioholic Samurai
The LSX should absolutely be run in a ported configuration. It's 4.5" midwoofer will run out of excursion real fast if it is tasked to play any bass at all. And it has even less surface area than a regular woofer since a chunk of its cone real estate is taken up by a tweetert.
Until you get a chance to actually hear a pair, reserve judgement. I do understand and agree with your statement, yet the LSX defies explanation as to how it performs as well as it does in such a small package.
 
KEW

KEW

Audioholic Warlord
The LSX should absolutely be run in a ported configuration. It's 4.5" midwoofer will run out of excursion real fast if it is tasked to play any bass at all. And it has even less surface area than a regular woofer since a chunk of its cone real estate is taken up by a tweetert.
Don't you think KEF has done something to control/protect from excessive bass?
I am thinking of the JBL LSR-305, which is pretty bullet-proof!
Since they have the sub output, it really would be nice if they offered a 100Hz XO.
If not, I could see plugging the port for a sealed configuration in order to force a higher roll-off point and protect them from over-excursion!
With such a small woofer, I can't see much likelihood of using them without a sub ... maybe very nearfield.
At $1100/pr, most people will buy a speaker better bass capability if they want a full range speaker.
I'd almost rather see KEF design the roll-off into the monitors and match a quality sub with these and sell a very competent 2.1 or 5.1 system (ala Energy Take system on steroids)!
 
KenM10759

KenM10759

Audioholic Samurai
The DSP in the LSX does indeed limit excursion, among the myriad other things it can do. I don't know if it's a fixed subwoofer crover point or not, haven't delved into it. Not going to either, because I have LS50's as near field monitors in my office. :)
 
S

snakeeyes

Audioholic Samurai
Don't you think KEF has done something to control/protect from excessive bass?
I am thinking of the JBL LSR-305, which is pretty bullet-proof!
Since they have the sub output, it really would be nice if they offered a 100Hz XO.
If not, I could see plugging the port for a sealed configuration in order to force a higher roll-off point and protect them from over-excursion!
With such a small woofer, I can't see much likelihood of using them without a sub ... maybe very nearfield.
At $1100/pr, most people will buy a speaker better bass capability if they want a full range speaker.
I'd almost rather see KEF design the roll-off into the monitors and match a quality sub with these and sell a very competent 2.1 or 5.1 system (ala Energy Take system on steroids)!
Not interested in a bookshelf with drivers that small unless it is for surround duty only. :)
 
John Parks

John Parks

Full Audioholic
Again, like @KenM10759 said, you should reserve judgement until you actually hear them. My KEF dealer had a pair (well, several, in all of the colors) and I gave them a listen in a large room from at least eight feet away. They played louder than what I am comfortable listening to and with no audible distortion. Granted, hooking up a sub (KEF R400b) filled in the lowest octaves nicely, but they sounded freakin' awesome on their own. I do not really picture them replacing my two channel rig (one never knows) but in a supplementary or desk top system, they rock. The built in amplification, in tandem with the onboard DSP is really something else.
 
S

shadyJ

Speaker of the House
Until you get a chance to actually hear a pair, reserve judgement. I do understand and agree with your statement, yet the LSX defies explanation as to how it performs as well as it does in such a small package.
It produces as much bass as it does because it uses a bass reflex design. I am saying that it wouldn't be able to were it a sealed speaker.
 
S

shadyJ

Speaker of the House
Don't you think KEF has done something to control/protect from excessive bass?...

If not, I could see plugging the port for a sealed configuration in order to force a higher roll-off point and protect them from over-excursion!
A sealed configuration would force it to get into much higher excursions much more rapidly to produce any bass at all. Far from protecting it, sealing it would drive it into gross distortion much more quickly.
 
KEW

KEW

Audioholic Warlord
A sealed configuration would force it to get into much higher excursions much more rapidly to produce any bass at all. Far from protecting it, sealing it would drive it into gross distortion much more quickly.
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)?
 
S

shadyJ

Speaker of the House
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.
 
Sheep

Sheep

Audioholic Warlord
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
 
KEW

KEW

Audioholic Warlord
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?
 
KEW

KEW

Audioholic Warlord
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.

View attachment 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!
 
KenM10759

KenM10759

Audioholic Samurai
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

KEW

Audioholic Warlord
This has been out long enough that I looked into the manual to address our previous concern about whether or not KEF provided the ability to apply a HPF to the L & R speakers.
The following is from page 28 of the user manual:
The Expert Mode lets you configure the EQ preferences in greater precision. They include:
• Desk Mode (On / Off, -6.0 dB to 0.0 dB)
• Wall Mode (On / Off, -6.0 dB to 0.0 dB)
• Treble Trim (-2.0 dB to 2.0 dB)
• Phase Correction (On / Off)
• Bass Extension (Less / Standard / Extra)
• High-Pass Mode (On / Off, 50 Hz to 120 Hz)
• Sub Out Low-Pass Frequency (40 Hz to 250 Hz)
• Sub Gain (-10 dB to 10 dB)
• Sub Polarity (+ / –)
When the settings are done, tap “Save” at the bottom of the screen and create a name for saving your sound profile.
The above is the "Expert mode" in the DSP phone app. According to the instructions for the "Basic mode" it simply asked for a yes or no as to whether a sub is attached. I might guess it then applies a fixed (80 or 100Hz?) HPF, but don't know!
 

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