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aty000
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Joined: Apr 6 2013 - 7:19am
Kef 207/2 tweeters died again

Hi all,

I have an issue with my Kef 207/2. For the second time the tweeter of both speakers stopped to work; no sound.

the first time I had the issue, the setup was: Onkyo 5008 preout -> CA-Classé 2200 -> Kef 207/2

the second time: Pioneer SC-LX86 preout -> CA-Classé 2200 -> Kef 207/2

both issues have been triggered by high volume (+10db on the Onkyo display the first time and +7db on the pioneer display the second time)

I love my loudspeakers, but now I am living with the fear they will burn again. The current work around is to limit the volume on the A/V receiver (sad enough, the pioneer have only 3 settings; -20, -10 and 0db).

You all will probably know much more then me in the area. Do you have any idea what the problem could be? Is really the Classé too much for the loudspeakers.

Please, let me know if you need any other information to better narrow down the problem.

Thank you,

aty000

aty000
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Joined: Apr 6 2013 - 7:19am
some more info

Hello, nobody has an idea?

Classé CA-2200 has following specs:

Power output 200W/ch continuous rms @ 8Ω, 400W/ch continuous rms @ 4Ω

Voltage gain 29.1dB

Sensitivity 1.4Vrms for rated output @ 8Ω

 

I suppose that the Pioneer SC-LX86 output in pre-out at 0db is 1.4V, so at +6db should be 2.8V. Would then the output of the power amp surpass the specs of the Kef 207/2? 

 

thx,

aty000

 

Demondog
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Joined: Feb 22 2009 - 5:01pm
I have lots of ideas, but this should be simple

Your amp is not too much for your speakers if used correctly, but if an input of 1.4 volts is required to reach its rated output, then any more than 1.4V will likely cause it to distort the signal, which is not good for your speakers. The pre-amp volume control is what most people use to avoid overloading the input of a power amp, regardless of the pre-amp's maximum output.

But I don't know all the details of your system, so maybe it's more complicated?

steve59
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tweeter failure

I am more familiar with older kef's but have read about the 207/2's and there's jumper wires to tweak the tweeters output and thats where I would start. My ancient 105/3's which i've beat the crap out of for 25+ years have only needed 1 tweeter replaced and that was from a short in my even older RGR amp. make sure those jumpers are where they're supposed to be maybe your amps are bypassing the crossover and feeding the tweeters the whole load. imagine the 1" driver trying to reproduce a 20hz signal.

commsysman
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Tweeter failures
aty000 wrote:

Hi all,

I have an issue with my Kef 207/2. For the second time the tweeter of both speakers stopped to work; no sound.

>
Please, let me know if you need any other information to better narrow down the problem.

Thank you,

aty000

I have seen this problem again and again, and in most cases the problem is ultrasonic oscillation of the power amplifier output stage at a high amplitude that burns the tweeter out.

It IS ultrasonic, which means you can't hear it; only by looking at the output of the amplifier with an oscilloscope can you prove that it exists (your dog might be driven out of the room by it...lol).

The CAUSE is a poor ground connection on the amplifier input cables; RCA cables that are not making a tight enough connection at one end or the other.

Cables should be TIGHT when pushing them into place, and the outer ground connector should be TIGHT on the chassis connector. They should NOT just slip into place easily. It should take a fair amount of force to push them into place.

Laen
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Joined: Mar 12 2015 - 6:24pm
Your KEF speakers are not the

Your KEF speakers are not the problem. The problem is your crappy PIONEER. The KEFs have a mind of their own and are rejecting this POS equipment.

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