Did I Just damage my LS50M?

[Mehdiem]

Today, I was changing cables and forgot to turn of the my amp, all of the sudden I heard a huge popping sound (I think my amp shorted). Later, I looked and I saw a shadow around the driver of my right LS50, the left one is intact. I haven't yet detect degradation in sound
quality but I'm worried, what caused this deformation and what should I do to ensure everything is ok?

 

[Doodski]

To test the speakers use a sine wave generator and sweep the frequency up and down while having your hand on the volume control to ensure as you scan up and down in frequency that you don't overdo the power output to the speakers. This is the best, most accessible and least expensive way to detect if a speaker(s) have any issue(s). When the tweeter is loaded with high frequency sound don't turn it it really loud.

 

[Mehdiem]

To test the speakers use a sine wave generator and sweep the frequency up and down while having your hand on the volume control to ensure as you scan up and down in frequency that you don't overdo the power output to the speakers. This is the best, most accessible and least expensive way to detect if a speaker(s) have any issue(s). When the tweeter is loaded with high frequency sound don't turn it it really loud.

Just used this at moderate volume, I don't hear any buzzing noise when sliding right and left. Does this mean it's ok? What should I look for?

 

[Doodski]

Just used this at moderate volume, I don't hear any buzzing noise when sliding right and left. Does this mean it's ok? What should I look for?

If there was a issue you would have heard it when the specific frequency would trigger the fault to show. So from your explanation it appears that you are good to go and no issue with your speakers. I ask though did you hear any cabinet resonance as you swept the speaker in the low frequencies? Did you see the woofer moving in and out with enough power from the amp to get it moving? It is sometimes heard even with what appears to be good speaker cabinets. I don't expect a KEF speaker to resonate but one never knows.

 

[Salt]

Buy a Umik1, measure the mighty damaged and the other speaker, and done.
Use the microphone further for optimizing room treatment and DSP settings.

 

[Penelinfi]

Most likely your amp put out a nice bit of DC if it blew up, forcing the cone hard to max excursion and deforming when the surround hit the limits. It may still work fine without noticeable sound quality difference though.

 

[Mehdiem]

If there was an issue you would have heard it when the specific frequency would trigger the fault to show. So from your explanation it appears that you are good to go and no issue with your speakers. I ask though did you hear any cabinet resonance as you swept the speaker in the low frequencies? Did you see the woofer moving in and out with enough power from the amp to get it moving? It is sometimes heard even with what appears to be good speaker cabinets. I don't expect a KEF speaker to resonate but one never knows.

I had put cushions foams (provided by manufacture) inside the port (as I'm using sub), I took them out I tried again and now I hear a crazy cabinet resonance at 55 HZ as if someone turned on a fan inside the cabinet. This does happen only with the deformed speakers. I'm not sure even if it's worth fixing it, I'm thinking if I should buy a new pair as they are on sale until the end of August.

 

[Doodski]

I hear a crazy cabinet resonance at 55 HZ as if someone turned on a fan inside the cabinet.

The speaker port may be chuffing and making noise or is it surely a vibrating cabinet noise?

 

[Doodski]

... and there may be loose wires inside the speaker vibrating.

 

[Salt]

What about is this bait?: a mighty divergence on a picture, or a mighty divergence in "55 Hz", ...
Feel free to continue.

 

[Mehdiem]

... and there may be loose wires inside the speaker vibrating.

I look inside from the port, it seems that inside insulation (foam) has shifted to one side. Maybe this is a cause of vibration? I don't dare or even know how to open the speaker. I'm afraid it voids the warranty (or warranty might be useless nevertheless)?

 

[Mehdiem]

What about is this bait?: a mighty divergence on a picture, or a mighty divergence in "55 Hz", ...
Feel free to continue

Do you mean I should ignore it?

I also thought LS50 frequency ranges is 75+ so 55HZ shouldn't be practical issue?

 

[Doodski]

I look inside from the port, it seems that inside insulation (foam) has shifted to one side. Maybe this is a cause of vibration? I don't dare or even know how to open the speaker. I'm afraid it voids the warranty (or warranty might be useless nevertheless)?

It might be the cause. Only you can determine that because you have them in hand per say. If it is in-warranty then this is a job for the KEF service tech to address.

 

[Mehdiem]

It might be the cause. Only you can determine that because you have them in hand per se. If it is in-warranty then this is a job for the KEF service tech to address.

Do you think something like this is covered under warranty? I'm afraid if I tell them the story (that I think they have been over driven) they say it's not cover under warranty. So if they wanna touch it assume they are gonna charge something close to the price of a new pair (when on sale). I bought them back in 2021

 

[FrantzM]

It might be the cause. Only you can determine that because you have them in hand per say. If it is in-warranty then this is a job for the KEF service tech to address.

I'd heed that advice. Whatever happened can't be good, if it so noticeably modified the driver. You may not hear anything just now, but...
If at all possible take it to a Kef service center or at the very least discuss this with Kef support...

Good luck.

Peace.

 

[FrantzM]

Do you think something like this is covered under warranty? I'm afraid if I tell them the story (that I think they have been over driven) they say it's not cover under warranty. So if they wanna touch it assume they are gonna charge something close to the price of a new pair (when on sale). I bought them back in 2021

I shared the same thoughts.. better be honest with them ... You post this, online,
They may still provide services

Peace.

 

[Mehdiem]

It might be the cause. Only you can determine that because you have them in hand per say. If it is in-warranty then this is a job for the KEF service tech to address.

I took another close look, I inserted a stick to see if I can move the foam and I noticed that foam is firmly attached inside, so I highly doubt it that foam had moved a a result of what happened. Maybe it was like this since I bought it? But I'm not sure maybe something else caused the vibration. I really don't want to go though their support, I assume they gonna ask me ship it to them at my own expense and after 2/3 weeks them gonna come back with a considerable repairing cost.

 

[Doodski]

View attachment 387256
I took another close look, I inserted a stick to see if I can move the foam and I noticed that foam is firmly attached inside, so I highly doubt it that foam had moved a a result of what happened. Maybe it was like this since I bought it? But I'm not sure maybe something else caused the vibration. I really don't want to go though their support, I assume they gonna ask me ship it to them at my own expense and after 2/3 weeks them gonna come back with a considerable repairing cost.

I don't believe you damaged the speaker when it went very loud before. I think the internals have some sort of resonating/vibrating thing and that has been there since new. KEF needs to know about the internal vibration but otherwise I don't think they need to know more.

 

[Mehdiem]

A quick update! First, thank you all for your help and guidance and special thanks to @Doodski for introducing the wave generator which helped me track down my issue.

I contacted KEF and and explained the situation, and they sent me a new driver within a week, free of charge, as I was still under warranty period. I'm so impressed with their service! They gave me instruction on how to swap it myself, but I asked them if they can introduce a repair shop to do it for me, and they sent me to their repair shop and they swap the driver at no cost! Amazing service!

 

[Kremmen]

A quick update! First, thank you all for your help and guidance and special thanks to @Doodski for introducing the wave generator which helped me track down my issue.

I contacted KEF and and explained the situation, and they sent me a new driver within a week, free of charge, as I was still under warranty period. I'm so impressed with their service! They gave me instruction on how to swap it myself, but I asked them if they can introduce a repair shop to do it for me, and they sent me to their repair shop and they swap the driver at no cost! Amazing service!

That really is incredibly good of KEF. I can only imagine how you felt when you heard the "huge popping sound". Yikes! I'm delighted things worked out so well for you and your speaker.