KEF Ls50 driver issue!

Stuart.W.D

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I can't make sense of it, I turned on the HiFi system tonight. Due to a hectic summer, this was the first time I attempted to play my hi-fi kit. I can't explain how this happened to the driver.
My ten-year-old and partner are not interested in my HiFi system and only use the Alexa wireless speaker in the kitchen. With no pets in the house, I'm lost to how this occurred. I prefer to use my Marantz PM8005 amplifier at the nine o'clock dial because I don't like listening at higher volumes. In May, I had my last listening session and everything was fine.

The warranty has expired and I no longer have the box for the LS50's. I'm uncertain about what to do now that these speakers are no longer available. My discovery this evening is very disappointing.
 

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Stuart.W.D

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Wayne, I recall this as well. I appreciate your input. I was uncertain about the outcome or cause of the defect in the other What Hi Fi member Ls50's. I am hopeful that I can acquire more information. Also sent an email to KEF.
 
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Stuart.W.D

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That would be great, Wayne. Thank you. I moved a pair of KEF Q150's from my TV set up into the Hi-Fi set up tonight, but they are lacking the treble of the Ls50's. Hopefully it's something that can be resolved with KEF.
 
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twinkletoes

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Sorry things like this don’t happen. And seeing as these have no grills I fail to see how this hasn’t been noticed since May? Anyhow these have either been hit/ fallen off the stand/shelf or seriously overdriven somehow.

Marantz has a “soft” turn of feature so doubt your amp has done this.

Sorry to say if this wasn’t you someone is telling you porkys as to what’s happened. I doubt kef would warrantied these even if they where within the warranty period.

Edit: are they near a heat source, such as window or radiator?
 

WayneKerr

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Sorry things like this don’t happen. And seeing as these have no grills I fail to see how this hasn’t been noticed since May? Anyhow these have either been hit/ fallen off the stand/shelf or seriously overdriven somehow.

Marantz has a “soft” turn of feature so doubt your amp has done this.

Sorry to say if this wasn’t you someone is telling you porkys as to what’s happened. I doubt kef would warrantied these even if they where within the warranty period.

Edit: are they near a heat source, such as window or radiator?
Read the old thread in my previous post, we were all condemning that owner too until we were all proven wrong.
 

Stuart.W.D

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Sorry things like this don’t happen. And seeing as these have no grills I fail to see how this hasn’t been noticed since May? Anyhow these have either been hit/ fallen off the stand/shelf or seriously overdriven somehow.

Marantz has a “soft” turn of feature so doubt your amp has done this.

Sorry to say if this wasn’t you someone is telling you porkys as to what’s happened. I doubt kef would warrantied these even if they where within the warranty period.

Edit: are they near a heat source, such as window or radiator?

I take the set up of my hi-fi extremely serious. My hi-fi components are on the opposite side of the room from the radiator. The defect driver is not near a window. The speakers are securely blue tacked to my Atacama stands which are filled, which prevents them from being knocked over. My amplifier does not exceed the nine o'clock dial and I do not possess any subwoofers in my setup. It's a strange situation, but it's also extremely disappointing.
 
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I’m not pointing fingers, but aluminium cones don’t deform for no reason, there’s always a cause. Used within their normal capabilities, it just won’t happen. They can stop working of their own accord for various reasons, but that’s rare. Deformation can be caused by an electrical surge (blown), physical damage(creases/dents/holes etc), or abuse by volume or bass levels (obliterated).

In the other thread, it’s definitely down to stress on the driver due to over-excursion, for whatever reason, as you can see where the damage is all round the edges of the driver where the cone is likely to flex the most. I‘ve only ever came across one pair that were trashed, and that was a chargeable repair - comes were stiff, and you could smell where the voice coils had fried, and the cones looked like a car crash - although that was quite early on in the life of the LS50, about 10 years ago. Maybe if there’s been a few too many instances of damage caused by stress on the driver and KEF feel a little guilty and treat some with a bit of leniency, I don’t know.
 
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Stuart.W.D

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Hi David, thanks for your message, I have a surge protection installed in my Hi-Fi setup. In this thread, I have mentioned the volume dial level multiple times. My belief is that my daughter and partner are both honest individuals, and they never come into contact with the system. As previously mentioned in my opening post, I had a busy summer taking a Human Resource Management IPA course that kept me occupied. May was the last time I had my system playing, and everything was fine. I initiated the thread to gain more knowledge, as I was both shocked and disappointed by the findings last night.
 

podknocker

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This is strange. I see the crease is at the top right of the cone. Any physical impact would have needed to come from below the speaker, or horizontally, as this part of the cone could not have been struck by anything falling from above.

I can't think how an aluminium speaker driver could just develop a crease, without being hit by something. Even doped paper cones don't tear, unless driven by massive amps at full volume, or underpowered amps, struggling with the speaker load and then start to clip etc.

I blew a pair of Tannoy 603 speakers decades ago, trying to get them to go loud with a 35WPC Kenwood amp. I learned a lesson that day.

KEF are proud of their speakers and I'm sure QC is tight. I can't explain it. Very unusual.
 
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WayneKerr

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This is strange. I see the crease is at the top right of the cone. Any physical impact would have needed to come from below the speaker, or horizontally, as this part of the cone could not have been struck by anything falling from above.

I can't think how an aluminium speaker driver could just develop a crease, without being hit by something. Even doped paper cones don't tear, unless driven by massive amps at full volume, or underpowered amps, struggling with the speaker load and then start to clip etc.

I blew a pair of Tannoy 603 speakers decades ago, trying to get them to go loud with a 35WPC Kenwood amp. I learned a lesson that day.

KEF are proud of their speakers and I'm sure QC is tight. I can't explain it. Very unusual.
Totally agree Pod, both these reported issues are difficult to understand or explain.
 

Stuart.W.D

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.

I blew a pair of Tannoy 603 speakers decades ago, trying to get them to go loud with a 35WPC Kenwood amp. I learned a lesson that day.

KEF are proud of their speakers and I'm sure QC is tight. I can't explain it. Very unusual.

I appreciate your perspective. I spent most of the night looking through various American sites and gathering information. These images, comprehend the appearance of a blown LS50 driver. The comparison is vastly different from my driver, which I'm putting down to a durability issue. The amplifier is not the culprit in this case.
 

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podknocker

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I appreciate your perspective. I spent most of the night looking through various American sites and gathering information. These images, comprehend the appearance of a blown LS50 driver. The comparison is vastly different from my driver, which I'm putting down to a durability issue. The amplifier is not the culprit in this case.
Wowzer!

I dread to think how loud these were pushed to cause that level of destruction.

When you hear clipping, or distortion, you turn the volume down.

Most of these issues are obvious signs of abuse and many people should know better.

Your KEFs are intact with just a bit of a crease. It's still a mystery to me.
 

Stuart.W.D

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The only thing I can do is wait for KEF's response. What worries me is that I have the original Ls50's that are now obsolete. I'm certain that the Meta driver will differ from the anniversary model.
 

Gray

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In May, I had my last listening session and everything was fine.
That's the mystery.
We know that metal expands and contracts.

You'll probably confirm Stuart, that they were not subject to any temperature extremes.....but who's to say that the temperature needs to be extreme?

Maybe there are loads of non-troubled cones out there.
Maybe they've just been lucky so far.
But who here would bet on their long-term futures?
And by long-term, I don't mean 10-15 years.
My long-term starts at 20 years.
 

podknocker

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I know polypropylene sounds different as the temperature changes.

I'm not sure about paper, or other materials.

For an aluminium cone to suffer, you would need to expose it to very high and/or cold temperatures.

It is crackers.
 

Stuart.W.D

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I recently discovered that I purchased them on 20 March 2019, not 2017 as I had previously thought. I have included a picture of the driver in natural daylight. @Gray - The speakers are located on the opposite side of the room from the radiator. My heating system is a kerosene oil tank located outside which heats the radiator. It is on for only one hour in the morning and one hour in the evening during the cold days. Due to the increase in oil prices in Europe.
 

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