I destroyed my KEF LS50s - how??

[kevlilly]

I'm slowly getting into building a system of nicer equipment to enjoy the sound of my vinyl collection. I recently purchased a set of KEF LS50s and have been loving them for about 6 months. Recently, had a few friends over and things got a bit loud. Next morning, woke to find that I'd put a sizeable wrinkle in one of the woofers and completely ripped through the other one. I mean, it's destroyed.

To be honest, I don't really think the music was on *that* loud and I'm wondering if there is something wrong with my setup or if I just gave them too much power. Hoping some of the more knowledgeable minds here could have a look and tell me what you think.

Setup:

Onkyo SR876 (140/channel) *but* I did have the speakers bridged so that I could set them at 8 ohms, which they are rated for. The only way to get the speakers at 8 ohms was to bridge them, which I understand doubles the power to them. I had my crossover set to 60 hz. I'm using a paradigm 12 cube for my sub.

I might have been listening to them at about -5 db, basic rock music, nothing too bass-y. Am I just putting too much power through them? I got them repaired (for $500) and now I've unbridged them, set the ohms at 4 and upped the crossover to 80 db. But I'm really flinchy now when I turn the volume up even slightly.

Thoughts? Thanks in advance!

 

[plastic penguin]

Welcome...

Try changing your friends.

No levity intended, but I've never heard of a cone (speaker material) to wrinkle unless someone has 'got at them'. I have a 40-year old pair of Wharfedales in my loft, which I used over a 20-year period: Parties, gettogethers, painfully loud and normal levels and they are still as new (not been re-covered, either).

 

[hg]

> Thoughts? Thanks in advance!

These are small desktop speakers that can produce clean reference levels at only 1m. That is, 85dB average with 20dB headroom for peaks, the sound level in a cinema. If you use them as main speakers and at party levels it is only reasonable to expect them to break. My advice would be to change them for a pair of main speakers.

 

[unsleepable]

How is that bridging thing that you did? It sounds like you bi-amped them, but then I don't get how that goes with the impedance thing that you mentioned.

When you are having fun with friends, chatting and not paying so close attention to the music, things can get loud quite fast. I've had to welcome the police at home more times than I think I deserved—although I'll admit I deserved a few. Still, I've never broken speakers but always played them with sufficiently powerful amplification—which your Onkyo seems to be.

The skeptic in me wouldn't absolutely disregard PP's advice about looking more closely to your friends either…

 

[steve_1979]

Welcome...

Try changing your friends.

No levity intended, but I've never heard of a cone (speaker material) to wrinkle unless someone has 'got at them'. I have a 40-year old pair of Wharfedales in my loft, which I used over a 20-year period: Parties, gettogethers, painfully loud and normal levels and they are still as new (not been re-covered, either).

My thoughts exactly.

Speakers/amplifiers driven past their limits usually blow a tweeter, burn out the woofers voice coils or something similar. Ripped cones sounds like drunk idiots to me.

 

[The_Lhc]

How is that bridging thing that you did? It sounds like you bi-amped them, but then I don't get how that goes with the impedance thing that you mentioned.

I also don't know how you'd do that when the LS50s only have one set of terminals on them, they're not biampable!

Aren't the woofers on these metal? How do you "rip" that?

 

[iQ Speakers]

A picture might give us all laugh, oh and add hypothetical theories as to what happened.

 

[Freddy58]

I think your (ahem) friends have done this. Hard to imagine blowing both of them, and you not noticing at the time?

 

[MickyBlue]

I think your (ahem) friends have done this. Hard to imagine blowing both of them, and you not noticing at the time?

i'm with freddy on this one, someone has fubar'd your speakers, nothing to do with the amplification.

 

[Vladimir]

Nothing to do with Kanye West, I'm sure. *acute*

 

[max337]

Man, that's harsh. Going from my own experiences, these are a nice, flashy, attractive pair of speakers. Built by a company renowned for building speakers. I find it incredibly hard to think any amplification could do that bar some Back To The Future type shenanigans.

Sorry to say, but as mentioned I'd first go with deliberate or accidental, human factors. Drunk ahole or jealous ahole. :/

 

[nirvy111]

Sounds to me like your friends keyed your speakers. No speaker covers and that nice tangerine coloured driver can be pretty tempting to some people, disfiguring that is. I have on occasion wanted to touch those drivers but had to tell myself to back down.

 

[MeanandGreen]

Vandalism, pure and simple!

 

[plastic penguin]

Or it could be that his so-called friends hate Dale Winton. *ROFL*

 

[Vladimir]

I've destroyed lots of speakers at parties and you have no idea some of the drivers are gone untill the next day, simply because you are dead drunk all night. However when you kill the amp, you notice immediatly.

If the drivers have actual physical damage to the cones/domes, that's someones elbow entry zone. No doubt about it. I've vacummed out lots of dustcaps and domes after parties. Unfortunatly, aluminium drivers are not as resilient as paper cones and silk dome tweeters.

 

[chebby]

Buy some cheapo speakers on ebay when you have a party coming up.

Then you can let your friends kick the living #### out of those instead with minimal financial loss.

 

[Anderson]

I'm curious to see the damage.

 

[kevlilly]

Ok, in an effort to give my friends the benefit of the doubt (you guys are really tough...) I've been doing some reading. Here's what I think happened:

I bridged the speakers. That means I pulled the power 2 unused surround channels (in a 7.1) system up to the front R/L speakers to double the wattage, taking them from 140 W to closer to 280 W. That's the only way I was able to get the impedance up to 8 ohms. But in doing so I probably just overloaded the power to the speakers. The amp requirements for the LS50s are 25-100W so I probably just blew them with 240W power. On top of that, I had the crossover set to 60 Hz, whereas the crossoer response is 79 Hz (with a range down to 47 Hz) - my limited understanding is that this would have been sending a lot more LF to the KEFs instead of to my sub.

All of that seems to add up to a pretty reasonable explanation for them blowing, right? Not trying to let my friends off the hook - just trying to make sure that I do all the necessary math now to make sure I don't do it again. Does that all sound reasonable, friends aside?

And just to give you all a laugh, pic below

.

Kevin

 

[kevlilly]

On the onkyo, you can bridge the front channels and the surround channels so that the front channels get double the power. It's different than bi-amping.

 

[kevlilly]

On the onkyo, you can bridge the front channels and the surround channels so that the front channels get double the power. It's different than bi-amping.

 

[Vladimir]

Overpowering them at the worst the voice coil will fry or fall appart from hitting the stops and they just stop working. The damage you described is not possible to do with just playing music.

Take a look at speaker destroying videos on Garret Claridge's channel. He tortures speakers in the worst possible ways with high power pro amps and they don't get damaged like you described. Only when he starts throwing them off his porch, chopping them with an axe, it really gets interesting.

 

[plastic penguin]

If you "fry" speakers it will always be the tweeter that blows before anything else. I remember seeing a friend do this to his dad's set-up many moons ago. And with this system it tone controls, with the bass cranked up to the max.

Not really sure why the OP has come on here to ask the question. If it was me I'd keep schtum and just replace the speakers. That isn't normal. I would part exhange the friends with ones that are wallet friendly.

 

[Vladimir]

However, what you really want to know is if you can damage your speakers using your amp configuration as is while playing very loud. The answer was already given. YES! Playing loud is playing loud, doesn't matter if it's at a party or not.

Those speakers will poo their diapers at any party simply because they are not meant to survive one. Doesn't even matter if you have a sub. Just don't use them to a party and don't play them too loud for too long. End of story. If you want more SPL, you don't buy small bookshelf speakers.

 

[hg]

All of that seems to add up to a pretty reasonable explanation for them blowing, right? Not trying to let my friends off the hook - just trying to make sure that I do all the necessary math now to make sure I don't do it again. Does that all sound reasonable, friends aside?

And just to give you all a laugh, pic below

I see an error message instead of an image.

If you put too much power into a driver it tends to melt the voice coil and slam the cone against the stops. Depending on the details of the driver construction the voice coil might pop out of the gap. Depending on the details of the driver the metal cone might get hot during sustained high power use. Wrinkled and split cones are not beyond the realms of possibility but are not what would normally be expected from too much power. Are the voice coils and tweeters still working? If so, it might be worth getting in contact with KEF and asking if this is a known failure. If so, they might replace them free. If not, KEF replacement drivers are usually reasonably priced.

 

[andyjm]

If you put too much power into a driver it tends to melt the voice coil and slam the cone against the stops. Depending on the details of the driver construction the voice coil might pop out of the gap. Depending on the details of the driver the metal cone might get hot during sustained high power use. Wrinkled and split cones are not beyond the realms of possibility but are not what would normally be expected from too much power.

Speakers don't have 'stops'

Overdriving leads to blown or distorted voicecoils. Beer leads to ripped cones.