That is correct Gray,why only this one speaker. I know I will probably get no joy from Kef,but if I buy a new driver is it going to happen again, or do I sling the kefs and keep to my Acoustic energy speakers
davidf
Well-known member
Signal level between channels can vary quite a lot during tracks, as can bass. More often than not, people will blow one bass driver, not both.
I appreciate your comments David,but if the driver is damaged,why does the speaker sound fine ,the only reason I noticed the damage was I noticed a shadow on the speaker and went to investigate. The damage could have been there for several weeks or months,the sound was fine.
Gray
Well-known member
Yes, you'd either need a drastic fault, or a careless owner to take out both.
I meant that there has been no obvious damage to other brands of speaker for him, despite them having been subjected to the same amp / music / level. That's his point.
Gray
Well-known member
The cone is visibly damaged Ray. Of that there is no doubt.
David hasn't commented on whether or not it will be audible, he's given his opinion on the cause of the visible damage, that's all.
No not both drivers blown just the other side of the faulty driver has started to crack ,the other speaker is perfect
Al ears
Well-known member
Gray
Well-known member
Ultimately, Kef themselves may be able to do little more than that.
(They're bound to say it's rare, regardless)
Al ears
Well-known member
Probably so but we on the forum are not going to solve this OP's issues....
davidf
Well-known member
Whether the issue would be audible would depend on the nature of the damage, and would probably be less audible with a stiffer aluminium cone, but again, it depends on the nature of the damage to the cone.
The fact that the cones are working tells me they haven’t been overdriven from a power point of view, but the type of damage - the outward curving around the edge of the cone due to the roll surround being pushed beyond its capabilities - points to a high level of bass being passed through them - this of course, could be within the power handling of the speakers. Think of it like playing a 100w amplifier at around 50w, which is fine, but then turning up the bass control to full.
Al ears
Well-known member
please see post #37
The OP is adamant the speakers have not be overdrive in any way, so your "high level of bass" is basically calling him a liar.
I for oneq fail to see how it could happen to only one speaker even if that is what it was.
davidf
Well-known member
I’m not calling him a liar, I’m just stating from experience the likely cause of what I see, based on decades of seeing his sort of thing, and the outcomes. My interpretation of the photos may differ from the story given. Over the decades, I’ve heard many stories about speakers self destructing under normal use, only to find out their kids had a party one weekend without their knowledge and caused the damage. Sometimes kids use their phone to stream some music and they’ve got their phone settings with extra bass etc, they get twitchy with the phones volume and just a moment can cause some damage. There’s numerous ways actual damage to cones can occur - just not when they’re used within their limits. We’ll see what KEF comes back with. He might be lucky - every now and again, a manufacturer might repair something as a good will gesture, but they won’t always make this clear - it’ll just be repaired “under warranty“. But a vertical tear in a stiff aluminium driver doesn’t look good to me.
Al ears
Well-known member
I didn't realise the L50 Meta had been around that long.
Point taken about unknown useage but it seems in this gentleman 's case it is unlikely.
whilst your knowledge is admirable and very valuable you are hypothesesing and, as I have said, it is not us that can solve the OPS issues.
Certainly it would be great to hear what KEF come back with If only to determine their sense of customer loyalty. I feel sure it will be peanuts to them to replace the drivers.
If bass response from a source is not specific to left or right channel can you explain why only one speaker suffers?
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davidf
Well-known member
It’s not only one speaker though is it. Both cones are exhibiting what I see as signs of excessive cone discursion (the rounded effect near the edge of the cone), and now both cones have split. Whether this splitting is a result of the first issue I mentioned, I don’t know, but I wouldn’t expect a tear like that to be brought on by the first issue. Either way, we’re dealing with an aluminium cone that is very strong under normal useage, and would only tear/split due to a physical impact or unusual stress. I’ve seen Q Series cones completely obliterated by massive overdriving, and I’ve seen cones that have had some physical impact. I’ve also seen cones with that ‘rounding’ around the edge of the cone too, which as I say, is caused by the cone trying to travel further than the roll surround will let it.
You can Google “damaged KEF bass cone“ and see some similar effects.
Al ears
Well-known member
davidf
Well-known member
Both speakers show the rounding off around the cone edges. I read post #74 wrong and thought the right one was splitting too - it’s the other side of the cone.
davidf
Well-known member
From seeing the photos in the first post, I presumed the two photos were showing the damage to the left cone and right cone separately, but they’re showing the same cone, which is where my confusion has come in. I’d like to see a close up photo of the right cone. If the right cone has zero deformation, that makes it all the more weird, as this wouldn’t happen to one cone unless there was some sort of channel imbalance where the right one doesn’t see the same level as the left. That would presume, of course, a signal present to cause high cone excursion in the first place.
AJM1981
Well-known member
firstly.. i support your point of view on how the damage originated by external abuse or an accident
It could theoretically be something like the speakers got damaged during transport and the crack bursted while playing. But that will be something to exchange thoughts over with the manufacturer and really hard to get a grip on.
I don't think that the average ls50 or ls50 meta listener that buys them for their fine articulated sound will play them at excessive eardrum piercing db levels, so it would be excessive within the limits of what is normal. Anything beyond that the speakers might be able to handle and probably got tested on that, but it doesn't make sense in most real world situations.
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Gray
Well-known member
Actually, that is not my point of view.
I had a private message exchange with the OP.
I put it to him that the vast majority of people would think the cone has had an external whack.
He explained his domestic situation and the extreme measures he takes in protecting his equipment (reminded me of myself).
All I can say is that I am as sure as I can be, that he has done nothing to cause the damage.
As has been pointed out, nobody here can give a verdict, but I sincerely hope he gets a favourable resolution.
Smokiro
Well-known member
Fit the camera with 24h recording of the system. Simple.
Infrared bulbs.
Jokes aside do what you know why ask strangers who advocate against your own feeling.
EOT
Infrared bulbs.
Jokes aside do what you know why ask strangers who advocate against your own feeling.
EOT
GSV Ethics Gradient
Moderator
I'm in uk at moment seeing my children for first time in 2years re covid ,so am going to give kef a ring while here. An interesting note ,I called into a hifi shop in Manchester yesterday,and discussed my problem with the manager. He said,"Your not the first and will definitely not be the last with this problem ", his opinion was that the cones are "Just to sensitive " and he wouldn't recommend them for that reason. Doesn't solve my problem but interesting to here from a dealer. Regarding my other speaker there is no sign of any damage whatsoever, will send picture when i get back. The dealer did say he didn't think i stood much chance of getting a replacement but was worth a try.
Something i haven't mentioned before but perhaps worth a mention is that around 50% of the 8 months I've had the speakers, they have been connected to a Pioneer M73/C73 Reference amp/ preamp which is about 35 years old and has a Class A output of 20watts,which I wouldn't have thought should have been an issue. Just another difficult thing to explain,but will see what sort of a response I get when i phone on Monday .
Al ears
Well-known member
This may be pertinent as it is possible you have damaged them by attempting to drive then with a amplifier outside of their specified limits.
Perhaps you could explain why a 100 watt speaker should be damaged by a 20 watt class A amp
Thanks
Thanks
Al ears
Well-known member
I have already posted the recommended requirements that KEF suggest for partnering amplifiers.
More damage to speakers is done by attempting to drive them with an underpowered amp than one that is too poweful.
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