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KEF Cadenza refurb / unknown driver?

 
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mcandmar
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Joined: 20 Mar 2014
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Location: Dublin, Ireland

PostPosted: Mon Jul 21, 2014 10:07 pm    Post subject: KEF Cadenza refurb / unknown driver? Reply with quote

Hello all,

I have lurking on here for a while trying to learn all i can about these speakers. I have a pair of Cadenzas that were put into storage about a decade ago when the foam around the main driver disintegrated. My plan is to replace main drivers, replace the caps on the crossover if needed, and then put them back into good use.

From what i have read/understood the main drivers should be B200's, and there seems to be two versions with big or small magnets? What i found are completely different to any KEF drivers i have seen here or on eBay. There is no markings on them other than a W on the base, and 8ohm on the back of the cone. Can anybody identify them?

The tweeter is a SP1032, and the BRF is an SP1042 which i believe are original.

My next question is which drivers should i replace them with?

Mark

http://www.cr-x.org/temp/IMG_7445.JPG - Driver Magnet
http://www.cr-x.org/temp/IMG_7438.JPG - Driver Cone
http://www.cr-x.org/temp/IMG_7446.JPG - Tweeter
http://www.cr-x.org/temp/IMG_7453.JPG - Crossover
http://www.cr-x.org/temp/IMG_6464.JPG - Speaker front
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audiolabtower
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PostPosted: Mon Jul 21, 2014 11:46 pm    Post subject: Reply with quote

Those are just not kef drivers and have been replaced at some time in the past for whatever reason. I think they should have been SP1022.
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speakerguru
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Location: Green Hut, Tovil

PostPosted: Tue Jul 22, 2014 9:01 am    Post subject: Reply with quote

SP1032 Tweeter are correct. As Audiolabtower says, bass units should be B200 SP1022, which do have a very large, 120mm dia., ceramic magnet.

Last edited by speakerguru on Tue Jul 22, 2014 10:04 pm; edited 1 time in total
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mcandmar
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Joined: 20 Mar 2014
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Location: Dublin, Ireland

PostPosted: Tue Jul 22, 2014 8:48 pm    Post subject: Reply with quote

Thank you for the replies, looks like i'm on a hunt for some Sp1022's.

Any advice in regard to the crossover caps. They look like a film construction to me which makes me wonder if they are still good, or should i replace them anyway?

Cheers,

Mark
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speakerguru
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PostPosted: Tue Jul 22, 2014 10:00 pm    Post subject: Reply with quote

mcandmar wrote:
... crossover caps. They look like a film construction to me ....


All capacitors are film, being constructed of alternating layers of conducting and insulating films. Most types are relatively stable unless the breakdown voltage of the insulating layer is exceeded for any reason.

If you meant electrolytic capacitors, the insulating layer is an oxide formed by electrolytic action and this can deteriorate with age as the electrolyte dries. If there are symptoms which make you suspect them, you should measure them with an LCR meter (out of circuit) to determine if replacement is necessary.
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mcandmar
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Joined: 20 Mar 2014
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Location: Dublin, Ireland

PostPosted: Sat Jul 26, 2014 5:21 pm    Post subject: Reply with quote

speakerguru wrote:
mcandmar wrote:
... crossover caps. They look like a film construction to me ....


All capacitors are film, being constructed of alternating layers of conducting and insulating films. Most types are relatively stable unless the breakdown voltage of the insulating layer is exceeded for any reason.

If you meant electrolytic capacitors, the insulating layer is an oxide formed by electrolytic action and this can deteriorate with age as the electrolyte dries. If there are symptoms which make you suspect them, you should measure them with an LCR meter (out of circuit) to determine if replacement is necessary.


Thanks for reply. I was specifically interested to learn what the black Elcap's that are in the crossover are as they dont look like regular electrolytics to me?

In my hunt for main drivers i ended up winning another set of Cadenzas on eBay for 60 which totally made my day Very Happy

The cabinets are in very poor condition, and one of the tweeters has been pushed in but they are going to be a donor pair to replace the main drivers in my good set of cabinets.

I may also refinish those cabinets and stain them a dark wood colour without feeling guilty about it, and keep the good pair original. I will update progress as it happens..

Thanks again,

Mark
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speakerguru
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PostPosted: Sun Jul 27, 2014 11:26 am    Post subject: Reply with quote

mcandmar wrote:
I was specifically interested to learn what the black Elcap's that are in the crossover are as they dont look like regular electrolytics to me?

Elcaps and Alcaps used by KEF were both "reversible" electrolytic type capacitors.

These are made up of two regular electrolytic capacitors connected back-to-back in series in the same case. In this way only one is reverse biased at any one time. It does not get damaged because the other correctly biased one prevented reverse current to the reverse biased one.
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mcandmar
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Joined: 20 Mar 2014
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Location: Dublin, Ireland

PostPosted: Sun Jul 27, 2014 7:50 pm    Post subject: Reply with quote

Interesting, so they are bi-polar electrolytics then, only ever seen those in a metal can.

In that case i am just going to assume they are past their useful life span and replace them.

Many thanks,

Mark
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mcandmar
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Joined: 20 Mar 2014
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Location: Dublin, Ireland

PostPosted: Wed Aug 13, 2014 12:15 am    Post subject: Reply with quote

I received the 2nd pair of speakers, collection of Solen poly caps, and some new speaker cable last week so i spent most of Saturday afternoon rebuilding these.

I ended up using my existing cabinets and bass reflex units, main drivers from the donor pair, and also one of the tweeters as one of my originals had died, measures no resistance at all across it.

They cleaned up well in the end, and sound very clear to the point of being almost a little too bright at times. Really glad i put the time and effort into these, they are just so refined, i really do love the sound.

Thanks for all the help everyone, these speakers should live on for another decade or two of musical enjoyment.

Cheers,

Mark


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