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PostPosted: Wed Jun 13, 2018 4:21 am 
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Location: Lower Coverdale, NB, CA
i picked up a pair of KEF C35 speakers a couple years from an audiophile and they sounded perfectly fine when he demo'd them at his home on his Luxman amplifier. However when i got home, they sounded horrible, muddy, distant highs, and mostly low end. Unusable, even my wife agreed. I was using my Marantz 2216. Maybe its under powered I thought, so I tried them on my harman kardon theater amp (just to test on a higher wattage amp), same results. Finally i borrowed a Optonica SM-4000U, 145 watts at 4 ohm per channel. Again, same results.

Does anyone have any idea what could be wrong? Is it the speakers? Did something die inside, in both speakers?
I'm not an expert in any of this so any advice or help would be appreciated!
Thanks!
Ryan


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PostPosted: Wed Jun 13, 2018 4:38 am 
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Location: Stratford, PE, CA
I drive 4 OHM with a Nad 326 Amp and all is well.

Not to sound judgemental but do you have them connected in phase?Sounds like any of those amps should be able to drive the KEFs


Good luck

Alan


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PostPosted: Wed Jun 13, 2018 4:51 am 
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Location: Richmond Hill, ON, CA
The tweeters are probably not working.
Open them up, and get out your multimeter.
Check the resistances across the driver terminals. There should be a pair for the bass/mid and another for the tweeter. If you get continuity, the problem is likely tp be in the crossovers, possibly failed capacitors or connections.
You can also feed a low-level audio signal directly into the tweeters to make sure they are working.

Cheers,
Alec


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PostPosted: Wed Jun 13, 2018 5:29 am 
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Location: Lower Coverdale, NB, CA
Thanks guys
I believe they are in phase, i tried alternating the phase last night with no change. To absolutely rule that out, 1 speaker on its own should sound ok right?

Thanks for the wiring tip, ill take a peak inside tonight :)


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PostPosted: Wed Jun 13, 2018 6:42 am 
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Location: hawkesbury, ON, CA
if they sounded ok when you first listen to them with the luxman, they should sound still ok with your set up.unles you would have over driven them and blew something. but that should be obvious if let say a tweeter went faulty.so maybe, something else need to be checked, speaker positioning, quality wire, source being played, if he was playing sacd, and you play mp3, there will definitly be a difference.
what do you feel is different?


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PostPosted: Wed Jun 13, 2018 6:55 am 
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Location: Toronto, ON, CA
drhannah wrote:
i picked up a pair of KEF C35 speakers a couple years from an audiophile and they sounded perfectly fine when he demo'd them at his home on his Luxman amplifier. However when i got home, they sounded horrible, muddy, distant highs, and mostly low end. Unusable, even my wife agreed. I was using my Marantz 2216. Maybe its under powered I thought, so I tried them on my harman kardon theater amp (just to test on a higher wattage amp), same results. Finally i borrowed a Optonica SM-4000U, 145 watts at 4 ohm per channel. Again, same results.

Does anyone have any idea what could be wrong? Is it the speakers? Did something die inside, in both speakers?
I'm not an expert in any of this so any advice or help would be appreciated!
Thanks!
Ryan


Possibly a capacitor in series with the tweeter has failed?

First, check the resistance of the tweeters. If you have a capacitance meter, you can check the caps too. You can also tracing out the circuit with the ohmeter from beginning to end and see where it's busted. Note: You will not see a resistance across a capacitor, as the capacitor will block the DC voltage used by the ohmeter. It should show a reading from input at the speaker terminal to the input side of the capacitor.

If the capacitor has failed, and it is showing up as a short, the tweeter may have been damaged by the low frequencies.

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PostPosted: Wed Jun 13, 2018 7:03 am 
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Ya im starting to think the tweeters/capacitors are the problem. Just odd that they changed when i got home with them.

Thanks!


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PostPosted: Wed Jun 13, 2018 7:55 am 
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Unlikely.
Biwireable? Was original owner biwiring?
Jumpers? Did u install?

There's also the synergy thing...

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PostPosted: Wed Jun 13, 2018 9:31 am 
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each speaker only has a red and black post.

synergy?


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PostPosted: Wed Jun 13, 2018 11:25 am 
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Location: vancouver, BC, CA
The uni-Q tweeters on those fail all the time. They begin to gradually fade in output, and then die completely.
I can't account for how they sounded okay when you demo'd them (could the seller have cranked up the treble on his amp to compensate?)
But that is a speaker that is almost ALWAYS going to have tweeter problems nowadays.


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PostPosted: Wed Jun 13, 2018 11:30 am 
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Interesting Trent, thanks for the tip.
Ya the guy demo'd them in his garage, the big door was open so i could have been fooled in such an odd acoustic environment.


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PostPosted: Wed Jun 13, 2018 1:21 pm 
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Why not use some test tones, this would be good for the next time you audition some speakers.

Playing some frequencies from 5 hz to 20khz will determine if there are any flaws in the speakers.

You will not hear the lower tones, but you can see the woofers move.

There are a number of sites with tones that you can download.

Burn them to a disk, then let the testing begin.

https://www.focal.com/en/focal-teach/cd-focal-tools

http://www.wavecor.co.uk/testdisk.html

https://www.discogs.com/Various-Audio-Test-CD-1-91-Test-Signals-for-Home-and-Laboratory-Use/release/8312695

Regards
Ohms

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PostPosted: Wed Jun 13, 2018 1:31 pm 
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Location: toronto, ON, CA
Coaxial speakers?


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PostPosted: Wed Jun 13, 2018 2:02 pm 
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https://www.hifiengine.com/manual_library/kef/c35.shtml
Viewable if you login.

After a review of the manual, looks like the tweeters are ferrofluid cooled.

Chances are that this fluid has dried up, and the tweeter coils are now burnt out.

The tweeters go for around $125 on ebay, no guarantee how long they will last...

Regards
Ohms

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PostPosted: Wed Jun 13, 2018 3:54 pm 
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Joined: Mon Aug 08, 2016 5:46 pm
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Location: Markham, ON, CA
Just to be sure, they sounded fine, you drove home and hooked them up right away and they sound like crap? Doesn't sound like tweeter failure to me.....what are the odds that tweeters on both speakers fail on the drive home?


Call the seller and ask if you can try them again on his system...there is something more going on here....


Last edited by brownslane on Thu Jun 14, 2018 5:14 am, edited 1 time in total.

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