Kef ls50 meta cone cracking

rayolight

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Jul 21, 2021
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I have a pair of Kef ls50 meta speakers bought in October 2021,noticed this morning that the meta cone has cracked in one place and showing signs of cracking in other areas. I will contact my supplier to get it sorted under warranty, but am interested in what might have caused the problem. The other speaker is perfect . My amp is a Vincent sv-237mk. I would be interested to hear if any other member has had a similar problem
 

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Gray

Well-known member
Is it the left-hand speaker in that bottom picture?
Nothing to do with direct sunlight?
If it were a common problem, others would surely be reporting it 🤔

PS at least you've got two other pairs to switch to.
 

rayolight

Well-known member
Jul 21, 2021
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Is it the left-hand speaker in that bottom picture?
Nothing to do with direct sunlight?
If it were a common problem, others would surely be reporting it 🤔

PS at least you've got two other pairs to switch to.
Yes Gray it's the left hand speaker but window has curtains drawn all the time and doesn't get direct sunlight, actually the right hand gets more direct light and it's fine. Never experienced anything like this ,have written to kef for some input.
 
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twinkletoes

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Nov 16, 2021
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All the hallmarks of being overdriven I'm afraid you can see the deformation at the top of the first photo (ripple near the rubber surround where the cone has bent outward because the rubber can't go any further) and it can just affect one speaker as stereo pairs don't receive the same load all of the time. Seen plenty like this, especially with metal coned subwoofers. , i'd be very surprised if they do replace under warranty, it will be an extreme case of goodwill if they do.

But good luck hope you get back up and running soon. Though you have other speakers so not all doom.
 

rayolight

Well-known member
Jul 21, 2021
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Looks almost like physical damage doesn't it?....but you obviously know it isn't.
Good luck. Your case will be followed by many I'm sure.
Yes,that is a worry, will be a test to see what the response is from the distributor. I've had my AE1'S for 40 years and never had a problem, will let you know the outcome
Cheers
 
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All the hallmarks of being overdriven I'm afraid you can see the deformation at the top of the first photo (ripple near the rubber surround where the cone has bent outward because the rubber can't go any further) and it can just affect one speaker as stereo pairs don't receive the same load all of the time. Seen plenty like this, especially with metal coned subwoofers. , i'd be very surprised if they do replace under warranty, it will be an extreme case of goodwill if they do.

But good luck hope you get back up and running soon. Though you have other speakers so not all doom.
quite possibly although I am curious as to how his amp could do this.
 

nopiano

Well-known member
Without knowing their background, I must say that they look like they’ve been whacked, and hard. I can’t believe that damage could arise from overdriving, as surely the voice coil would expire?

I hope for your sake that KEF agree with your diagnosis. Do let us know.
 
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twinkletoes

Well-known member
Nov 16, 2021
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quite possibly although I am curious as to how his amp could do this.
Any amp will do it especially if it receives a large phase reversal or sudden dynamic swing. Kef cones by design can’t move too far they certainly have a sudden stop. Almost to the point that would be happier in a sealed enclosure.

That crack is fatigue not an impact zone
 
Any amp will do it especially if it receives a large phase reversal or sudden dynamic swing. Kef cones by design can’t move too far they certainly have a sudden stop. Almost to the point that would be happier in a sealed enclosure.

That crack is fatigue not an impact zone
I'll take your word for it. A poor design then?
As the OP says his other speakers are fine....
 

Gray

Well-known member
That crack is fatigue not an impact zone
Give me an axe and I'll show you some similar looking 'fatigue' 😆

Seriously though, do we think Kef are going to come back with an official verdict of fatigue?
If so, there will be more such cases, because plenty of people play at excessive levels.
 
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Give me an axe and I'll show you some similar looking 'fatigue' 😆

Seriously though, do we think Kef are going to come back with an official verdict of fatigue?
If so, there will be more such cases, because plenty of people play at excessive levels.
To be frank if the amp is within the speakers recommended parameters the speaker should be able to handle those levels.....
 

Gray

Well-known member
To be frank if the amp is within the speakers recommended parameters the speaker should be able to handle those levels.....
In my old service dept. we judged speaker overload by the condition of the voicecoil.
Some of those 12 and 15" drivers got a real pasting out on the road with bands. No cone suffered - but then that was in the days before 'improved' cone materials 🙄
 
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In my old service dept. we judged speaker overload by the condition of the voicecoil.
Some of those 12 and 15" drivers got a real pasting out on the road with bands. No cone suffered - but then that was in the days before 'improved' cone materials 🙄
Perhaps so but this is a domestic standmount from a very reputable company.
 
It’d be nice to see a full photo of the drivers, but the first pic looks like external damage, the second pic looks like overdriving/fatigue. Fatigue doesn’t necessarily take place outside of the speaker’s and amplifier’s power limits - play bass heavy music, causing the drivers to move out further than theyre comfortable with, and you’ll end up with what looks like the right sided photo. A speaker like this should be used carefully in larger rooms or at higher volumes, and really, anyone wanting high output levels with heavy bass output should really be looking at another speaker. This is where a good dealer comes in, and shows the downside of buy-whatever-you-like mail order.
 

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