Kef ls50 meta cone cracking

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rayolight

Well-known member
Jul 21, 2021
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I can't comment too specifically on the speaker (being from another manufacturer) but it's feasible for the cone to have been damaged that way in use - you have a powerful amp and vinyl in particular can put out some hefty low frequency information (not always audible) which can really push a smaller speaker driver even at modest volume. I experienced this happening first hand on very early AE1 mkIII's.

It's certainly the case you may not hear any obvious ill effect, there will be air leakage and the break-up/stiffness/dispersion will have altered but if the coil is undamaged it can be surprisingly subtle. If indeed the coil is undamaged it's another sign they may not have been overdriven for warranty.

The dealer should be your first port of call - they know you as a good customer and will be able to talk to their KEF rep. They may want to inspect the speakers and have them in for repair, at worst you may have to pay for a new driver if they determine it as "user error". Often it's at the dealer/manufacturer's discretion when the cause isn't obvious.

If you let me know your AE1 serial numbers I'll tell you the day they were made to clear up any confusion as to their age. ;)
Hi Serial number 01001473 and 01001474
 

Edbostan

Well-known member
Aug 5, 2021
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I'm not very hopeful as I agree it does look as though the speaker has been damaged, which i can assure you it hasn't. Am sure the supplier will do everything he can to get out of replacement. According to kef the speakers are guaranteed for 5 years and I have only had them since last October, perhaps they should send a disclaimer if you play level 42 music. At a push I think I can join the tear with superglue. As I have mentioned before, there is actually no noticeable degradation in sound to my ears which I find amazing. It was only by chance I noticed the tear. Will have to wait and see 👀
Kef will find the problem by taking out the cone and inspecting the back of the cone. Kef must have the speakers returned for you to get a definite answer.
 

rayolight

Well-known member
Jul 21, 2021
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I'm very happy for kef to do a full investigation, I have nothing to hide,as I've already posted the speaker sounds fine even with the damage to the meta material. Had I caused the problem I wouldn't have even posted the issue and would have happily paid for a replacement driver. What worries me is why it happened and will it happen again especially if I have to pay for a new driver
 
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Edbostan

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Aug 5, 2021
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I'm very happy for kef to do a full investigation, I have nothing to hide,as I've already posted the speaker sounds fine even with the damage to the meta material. Had I caused the problem I wouldn't have even posted the issue and would have happily paid for a replacement driver. What worries me is why it happened and will it happen again especially if I have to pay for a new driver
The speakers are under warranty so of course the retailer is the first contact because the contract of sale is between them and you. This is where the chain of information will breakdown and an answer from Kef may be lost.
 

rayolight

Well-known member
Jul 21, 2021
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The speakers are under warranty so of course the retailer is the first contact because the contract of sale is between them and you. This is where the chain of information will breakdown and an answer from Kef may be lost.
That is my main concern, and is why I have contacted Kef direct to hopefully get a fair hearing
 

rayolight

Well-known member
Jul 21, 2021
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Your AE1's were made on the 2nd of August 1988. Glad to hear they're still going strong! (y)
Thanks for that Jim,they have been amazing. I am now also the proud owner of a pair of AE500'S, had a few standing wave problems at first but Mat Spandl was invaluable in helping sort it out absolutely love em. The problem was resolved with putting a sock in the baffle😅,it has now been replaced with a purpose made foam strip.
Just one thing you might be able to advise, if I don't get a good response from kef,am thinking of just putting a thin stripe of superglue along the tear to stop it getting any worse. As I said before there is little to no noticeable change in the sound so can't see any point in the hassle with shipping it back to the supplier and having the driver replaced or do you think I should just leave it as it is and see what happens. Your comments would be much appreciated. Thanks
 
Thanks for that Jim,they have been amazing. I am now also the proud owner of a pair of AE500'S, had a few standing wave problems at first but Mat Spandl was invaluable in helping sort it out absolutely love em. The problem was resolved with putting a sock in the baffle😅,it has now been replaced with a purpose made foam strip.
Just one thing you might be able to advise, if I don't get a good response from kef,am thinking of just putting a thin stripe of superglue along the tear to stop it getting any worse. As I said before there is little to no noticeable change in the sound so can't see any point in the hassle with shipping it back to the supplier and having the driver replaced or do you think I should just leave it as it is and see what happens. Your comments would be much appreciated. Thanks
Could it be that the KEFs need a sock?
 

rayolight

Well-known member
Jul 21, 2021
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For vinyl I have a Michell Transcriptors Reference with Ortofon 540mk2 cartridge and Clearaudio Concept with mm v2 cartridge, my Vincent sv-237mk amp does not have a rumble filter, i also stream with Cambridge CXN v2 streamer and S.MS.L SU9 DAC,
 
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plastic penguin

Well-known member
For vinyl I have a Michell Transcriptors Reference with Ortofon 540mk2 cartridge and Clearaudio Concept with mm v2 cartridge, my Vincent sv-237mk amp does not have a rumble filter, i also stream with Cambridge CXN v2 streamer and S.MS.L SU9 DAC,
That's some kit you have there. I'm a big fan of ClearAudio, owned two of their cartridges, the Classic Wood Aurum and the Concept MM V2.
 

AEJim

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Nov 17, 2008
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Thanks for that Jim,they have been amazing. I am now also the proud owner of a pair of AE500'S, had a few standing wave problems at first but Mat Spandl was invaluable in helping sort it out absolutely love em. The problem was resolved with putting a sock in the baffle😅,it has now been replaced with a purpose made foam strip.
Just one thing you might be able to advise, if I don't get a good response from kef,am thinking of just putting a thin stripe of superglue along the tear to stop it getting any worse. As I said before there is little to no noticeable change in the sound so can't see any point in the hassle with shipping it back to the supplier and having the driver replaced or do you think I should just leave it as it is and see what happens. Your comments would be much appreciated. Thanks
No probs! Ahh yes, the deeper port tuning on the 500's could certainly cause room issues, they go around 15-20Hz lower than the AE1's. Sealing the port with anything will do - we often recommend a sock or rag to test it out before trying something more permanent.

Funny you ask that - while I was digging through the old serial numbers this morning I mentioned it to Mat and he immediately said "just put some superglue on it"! :) (admittedly he hasn't seen the pics) It's far from ideal of course but will seal the air gap and help prevent further damage in the short term. I'm absolutely sure KEF will sort the problem once they're on it though.
 

12th Monkey

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Aug 31, 2015
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Just one thing you might be able to advise, if I don't get a good response from kef,am thinking of just putting a thin stripe of superglue along the tear to stop it getting any worse. As I said before there is little to no noticeable change in the sound so can't see any point in the hassle with shipping it back to the supplier and having the driver replaced or do you think I should just leave it as it is and see what happens. Your comments would be much appreciated. Thanks
If you do anything to it, their response might be affected - leave until you hear. If they will fix it, I'd take them up. You won't be able to move them on in future looking like that - might not be a consideration now, but may be in future.
 
No probs! Ahh yes, the deeper port tuning on the 500's could certainly cause room issues, they go around 15-20Hz lower than the AE1's. Sealing the port with anything will do - we often recommend a sock or rag to test it out before trying something more permanent.

Funny you ask that - while I was digging through the old serial numbers this morning I mentioned it to Mat and he immediately said "just put some superglue on it"! :) (admittedly he hasn't seen the pics) It's far from ideal of course but will seal the air gap and help prevent further damage in the short term. I'm absolutely sure KEF will sort the problem once they're on it though.
Best not use Superglue until KEF have answered one way or another.......
Apologies, just seen the post above.
Strongly agree.
 

Gray

Well-known member
...all down to Kef now.
If they take you at your word, you'll be OK.
But their action needs to strike a balance between customer service and their own interests.
Of course, good customer service is in their interest - but replacing future (physically damaged) drivers for others, wouldn't be.

If the official verdict is misuse, then that misuse has been on one channel only 🤔
 
Any amplifier can cause damage to any loudspeaker if used incorrectly. Overpowering a speaker with an underpowered amplifier, or overpowering a speaker with an amplifier that is too powerful for the speaker. Each will cause different damage if not used within their capabilities.
That's a generalisation, the case in point is, is that possible with this amp and speaker specification ??
I do notice KEF recommend amplifiers between 40-100 wpc
The Vincent's spec complicates matters as it quotes 10 wpc in Class A and 150 in Class A/B
 
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rayolight

Well-known member
Jul 21, 2021
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Your AE1's were made on the 2nd of August 1988. Glad to hear they're still going strong! (y)
That's a generalisation, the case in point is, is that possible with this amp and speaker specification ??
I do notice KEF recommend amplifiers between 40-100 wpc
The Vincent's spec complicates matters as it quotes 10 wpc in Class A and 150 in Class A/B
Well, here we go ,it looks like the other side of the cone is starting to crack and its definitely not being overdriven, and certainly not been thwacked
 

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Gray

Well-known member
Any amplifier can cause damage to any loudspeaker if used incorrectly. Overpowering a speaker with an underpowered amplifier, or overpowering a speaker with an amplifier that is too powerful for the speaker. Each will cause different damage if not used within their capabilities.
That's all true of course David.
But (presumably) he's put the same signal, at the same level into his other speakers with no such (obvious) ill effect.
That's surely what this is all about.
 
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