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Multi-Way Conventional loudspeakers with crossovers

KEF 104/2 cap replacement
KEF 104/2 cap replacement
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Old 16th January 2019, 05:07 PM   #11
Lojzek is online now Lojzek  Croatia
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Quote:
Originally Posted by diyrob View Post
Hi - just wondering if there are any quick opinions on replacing caps on a pair of old Kef 104/2's...
The budget is low...

Before purchasing any new caps, if I were in your place, I'd first measure all the caps for capacitance. Nothing to lose, only gain more experience DIY-ing stuff.
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Old 16th January 2019, 05:58 PM   #12
chromenuts is offline chromenuts  United States
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I spent quite a bit of time researching this same question.

I have a bi-wire pair of the 104/2 that I picked up abandoned at a repair shop after they had the woofer surrounds replaced.

My crossovers are accessed by turning the speaker on its side and removing a panel on the bottom of the speaker.

I read various discussions about the tweeters, some on here. There are substitutes that have been used successfully. One was made by Vifa of which I have a pair sitting on a shelf. There is also currently a vendor on eBay selling “replacements” that look to be virtually the same driver with its faceplate removed and some foam tape applied to the face for $45 each I think.

The thing about these crossovers that I read is that they had there components painstakingly matched to very close tolerances (2% or better I believe) at great time and expense in the KEF factory. The general opinion that was voiced was that it would be pointless to just start ordering replacement caps that have the same values as they would never match the accuracy of the original caps and it would be impossible to obtain the same crossover performance which in a fourth order design like this would be very obvious. These are not my words, just what I found on the subject.

I also found the Falcon recap kits. They originally listed that they had a limited supply of kits that approached the factory selection standard of about 2%. When I sent an inquiry I got no response. I think the kit they still list has a 5% selection standard.

My feeling about the KEFs has been tainted by my involvement with other speaker projects that I have attained some very desirable results with. I haven’t let them go. They have been retained for HT use. If they start sounding really bad or something craps out I will probably take a shot at restoring them.

I’d try the replacement tweeters I have first and then order some ferrofluid to try and restore the originals. As others have said, I’d inspect and measure the original caps for leaks/variances first before replacing them. If it ain’t broke don’t fix it.
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Old 16th January 2019, 08:18 PM   #13
diyrob is offline diyrob  United Kingdom
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thanks for your reply - very interesting
falcon told me they only have the 5%
I will go for ferrofluid replacement with tweeters, though note falcon recommend Audax TWO25A2 as an exact replacement - about $100 a pair
Its quite a job taking these speakers apart - I did it today - so while I'm in there I'm tempted to replace caps anyway, particularly as am doing the job for a friend who wants them to last 'forever' - they may still be OK now but more unlikely when they reach 50, and he may not have the free help I am giving him at the moment.
If I had access to precision cap checking equipment I might take a different approach, but I don't.
I've an inkling these speakers need careful pairing...
R





Quote:
Originally Posted by chromenuts View Post
I spent quite a bit of time researching this same question.

I have a bi-wire pair of the 104/2 that I picked up abandoned at a repair shop after they had the woofer surrounds replaced.

My crossovers are accessed by turning the speaker on its side and removing a panel on the bottom of the speaker.

I read various discussions about the tweeters, some on here. There are substitutes that have been used successfully. One was made by Vifa of which I have a pair sitting on a shelf. There is also currently a vendor on eBay selling ďreplacementsĒ that look to be virtually the same driver with its faceplate removed and some foam tape applied to the face for $45 each I think.

The thing about these crossovers that I read is that they had there components painstakingly matched to very close tolerances (2% or better I believe) at great time and expense in the KEF factory. The general opinion that was voiced was that it would be pointless to just start ordering replacement caps that have the same values as they would never match the accuracy of the original caps and it would be impossible to obtain the same crossover performance which in a fourth order design like this would be very obvious. These are not my words, just what I found on the subject.

I also found the Falcon recap kits. They originally listed that they had a limited supply of kits that approached the factory selection standard of about 2%. When I sent an inquiry I got no response. I think the kit they still list has a 5% selection standard.

My feeling about the KEFs has been tainted by my involvement with other speaker projects that I have attained some very desirable results with. I havenít let them go. They have been retained for HT use. If they start sounding really bad or something craps out I will probably take a shot at restoring them.

Iíd try the replacement tweeters I have first and then order some ferrofluid to try and restore the originals. As others have said, Iíd inspect and measure the original caps for leaks/variances first before replacing them. If it ainít broke donít fix it.
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Old 16th January 2019, 10:24 PM   #14
Lojzek is online now Lojzek  Croatia
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No specialized precision equipment, a multimeter able to measure from 0Vrms and up, one resistor, a laptop headphone out, a sine wave frequency generator software (REW) and some hook-up wire (mini mono or stereo plug). After that some calculations and you are done.
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Old 16th January 2019, 10:58 PM   #15
Max Headroom is offline Max Headroom  Australia
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Location: West Australia, near to the beach, natural ambient sounds mostly.
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Old 18th January 2019, 07:43 AM   #16
diyrob is offline diyrob  United Kingdom
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very interesting and informative page - thanks for link




QUOTE=Max Headroom;5667186]Archived Projects


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Old 6th February 2019, 10:57 PM   #17
diyrob is offline diyrob  United Kingdom
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Thanks for everyone's input. In the spirit of sharing my findings;
Given my friend wants to keep these 'forever' I changed all the caps - some of which were showing signs of slight swelling..
Donuts and ferro done. grommets replaced. 13+14 Janzen crosscap 7.5uf. 15,16, 8, Janzen MKP, 6&7 mundorf plain ecap, all others alcap.
significant overall improvements reported, particularly detail and clarity in mid, extension and clarity in treble, all without detriment to character of the speaker. total cost inc. delivery charges just under £200. Given you can get a set of these for £3-400, surely this makes for a bargain proposition for budget high-end...?
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