Key ls50 speakers destroyed

Anyone else have this issue


  • Total voters
    2

RoccoLB

Standard Member
I purchased 2 kef ls50 speakers and attached them to a Sony STR za2100es receiver. This sound system was for my 65 inch tv system. The sound was never that good. After a few months my speakers stopped working and the plastic fronts were blown out, completely broken. I posted the picture below. Has anyone else ever seen this. I brought the speakers and receiver to a local audio store and they are shocked that this happened they have tested the receiver with another set of speakers and found no problems.
 
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Hillskill

Moderator/Games Reviewer
Pretty sure someone else posted a similar fault. Have you spoken to Kef?
 

dollag

Well-known Member
without knowing the rest of your system, i personally would not be using ls50's with that avr.

they are very hard to drive and often drop down to 3ohms impedence and can be taxing on the avrs psu. the sony i believe has a 290w supply which really is not a lot when driving all channels. could be that the speakers were being under powered. probably why it didnt sound to great.

what is the rest of the sysetm??
 

Hixs

Distinguished Member
Sure someone hasn't been at them with a knife?
 

Paul7777x

Distinguished Member
without knowing the rest of your system, i personally would not be using ls50's with that avr.

they are very hard to drive and often drop down to 3ohms impedence and can be taxing on the avrs psu. the sony i believe has a 290w supply which really is not a lot when driving all channels. could be that the speakers were being under powered. probably why it didnt sound to great.

what is the rest of the sysetm??
I agree with above... but that damage is catastrophic!

It looks wilful and psychotic :eek:

Something, obviously, has gone quite literally, spectacularly wrong with the power behind that driver.

But I genuinely cannot imagine what exactly it might have been.

I should think Kef would be willing to replace it instantly from sheer embarrassment.
 

dollag

Well-known Member
My dad done the same thing by playing Spotify connect too loud by mistake. He stopped it pretty quickly but the driver was smashed albeit not as bad as the pic above

E4F3D3A8-B3D6-4C4F-9DA4-CA396FA35C41.jpeg
 

CowFun

Novice Member
Hi RoccoLB

I would like to suggest that judging from your setup, it is likely the amp that killed your speaker. And the likely scenario is clipping, when your amp could not handle the high level input, the signal is clipped, with resultant output to the speaker that is much higher than the max amp output of about 100w. You only need one instance of clipping to blow the speaker. And without the proper electric gauges and meters, it will be difficult to test.

Years ago I blew a beautiful English speaker with my receiver with 100w because of clipping. And that was the nth speaker blown in my family, all for the same reason.

I could probably reproduce the outcome using other speakers by cranking up the output to beyond what the amplifier is capable of handling.

Similarly, our house came with a home theatre with a receiver not unlike what I had years ago, and the speakers are gone, most likely as a result of clipping as well.

Fast forward many years, I finally learn the importance of a good amplifier. I now have a pair of stereophile 600w monoblock power amp driving these tiny ls50 and they sound wonderful. The receiver for my theatre system is also replaced by a good power amplifier. No clipping, louder than my ears can take, if I wanted to torture myself.

I purchased 2 kef ls50 speakers and attached them to a Sony STR za2100es receiver. This sound system was for my 65 inch tv system. The sound was never that good. After a few months my speakers stopped working and the plastic fronts were blown out, completely broken. I posted the picture below. Has anyone else ever seen this. I brought the speakers and receiver to a local audio store and they are shocked that this happened they have tested the receiver with another set of speakers and found no problems.
 

RoccoLB

Standard Member
Thanks CowFun, I'll pass this along to my audio guy. I'm not an audio expert, but this makes sense to me. Surely I can't be the only one in the world to have this problem. So far we are not getting much support from the KEF folks, with the exception that they wondered if some small kid destroyed them. Currently I live alone and so far my dog does not know how to use a sharp object.

Thanks again.
 

CowFun

Novice Member
If you are trying to get kef to fix the speaker for you, then I wouldn't suggest to them it is clipping,which means the problem is your amp, not the speaker.

Thanks CowFun, I'll pass this along to my audio guy. I'm not an audio expert, but this makes sense to me. Surely I can't be the only one in the world to have this problem. So far we are not getting much support from the KEF folks, with the exception that they wondered if some small kid destroyed them. Currently I live alone and so far my dog does not know how to use a sharp object.

Thanks again.
 

muljao

Well-known Member
That looks like a very high current rushed through and blew them, more than (I would have thought) any amplfier should supply.
 

Symphy944

Active Member
without knowing the rest of your system, i personally would not be using ls50's with that avr.

they are very hard to drive and often drop down to 3ohms impedence and can be taxing on the avrs psu. the sony i believe has a 290w supply which really is not a lot when driving all channels. could be that the speakers were being under powered. probably why it didnt sound to great.

what is the rest of the sysetm??
This could be the problem in deed. Asking to much current because of low impedance can cause a basic amplifier to clip. On such moments it delivers peaks of DC current which can hurt your speakers.
My previous amp destroyed the tweeter in my center speaker because of this.
 

noiseboy72

Distinguished Member
Clipping effectively "squares" off the waveform, so the speaker has to stop and start very quickly, which can cause it to fail due to high current combined with the voice coil leaving the protection of the magnetic flux.

Lots of 4 Ohm speakers drop to 3 Ohms at some frequencies, so this combined with a modestly powered amplifier should not be a big issue, but if you run it loud, you do run this risk.

It does look like the speaker does have a design issue in that the voice coil can push the cone far enough to destroy the surround and cone in that way. Occasional clipping should not cause this and the distortion would be very evident. There really doesn't appear to be much evidence of physical damage and it seems unlikely that 3 speakers would suffer the same damage.
 
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Symphy944

Active Member
Most AV receivers are not designed for 4 ohm loads. Most state 6-8 ohm as minimal nominal impedance. I can’t find the minimal requirements for the 2100es, but specifications are indicated starting from 6 ohm.
But looking at the specs of the 2100es, it would surprise me if he ran out of juice. Maybe this Kef’s where set up as full size speakers and just couldn’t handle the power...
 

Paul7777x

Distinguished Member
Most AV receivers are not designed for 4 ohm loads. Most state 6-8 ohm as minimal nominal impedance. I can’t find the minimal requirements for the 2100es, but specifications are indicated starting from 6 ohm.
But looking at the specs of the 2100es, it would surprise me if he ran out of juice. Maybe this Kef’s where set up as full size speakers and just couldn’t handle the power...
Quite the opposite most likely.
 

Paul7777x

Distinguished Member
Not quite sure what you mean...? But...

Its actually easier to break a driver with too little power than too much.

And the Sony is quite feeble.

Add that to the well documented current requirement of the LS50s and Noiseboys answer (#16) seems most likely without being there at the time.
 

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