KEF Corelli crossover rebuild SP1052 + Schematic

[battradio]

I traded for a pair of KEF Corelli speakers and got them home and they just didn't sound correct .

http://www.audiokarma.org/forums/showthread.php?t=592200

And found out one of the crossovers had been replaced with the correct replacement crossover but it still didn't sound correct .

The former owner sent me the original crossover , and the other one he purchased and learned of the melted over heated inductor L2 on each crossover .

I replaced the caps on the two Crossover boards with the good inductors , measured all three on each board with a Meterman LCR555 and drew out the schematic




The over heated inductors had changed value from 2.1 Mh to .375 Mh on one and .265 Mh on the other .

Having the bad crossovers i decided to repair them also by winding new inductors .My first try was made from the barrel of an ink pen and gator aide caps .

Went to the local ACE hardware and purchased nylon washers and spacers and glued them together to make bobbins with gorilla glue










You can see that the insulation came off of the wire due to the heat



The orange bobbin was the prototype , the two larger ones use larger wire gauge , but have the same inductance ,that i will keep for spares .






The totally rebuilt crossovers . The original 30 uf 50 volt caps were tiny compared to the other caps on the board and must have had a terrible power factor and ESR compare to the other caps used .


The only schematic i could find on line was totally wrong for these speakers so i want the part number in the title so if someone else does a search it will pop up .

Will most likely make a pair of speakers with these crossovers if i can find a suitable tweeter .

The Corelli's are now a joy to listen to .

 

[Lavane]

Nice work Mark! :thmbsp:

 

[tyella]

Holy cow! Well done, sir. Those speakers found the right home for certain!

 

[leray1]

I've got Corellis but they're the SP 1051 Type. What's the difference?

 

[battradio]

Post a photo of the crossovers we will take a look .

Every KEf part at that time had a SP number , the whole speaker assy is most likely SP 1051 and the crossover is SP1502

http://kef.com/uploads/files/en/museum_pdf/70s/Corelli_Installation_Instructions2.pdf
http://kef.com/html/en/explore/about_kef/museum/1970s/Corelli_Calinda_Cantata/index.html

 

[toxcrusadr]

Just ran across this thread, well done! This is why I keep every inductor and discarded junk crossover I run across, in case I ever need one. I have about a dozen pairs so next time you need one let me know, I might have it. In any case the tutorial on DIY inductors is great.

 

[leesonic]

Nice work rewiring the inductors. I'll have to remember that tip using the nylon washers.

Lee.

 

[battradio]

Thanks for the nice comments , these speakers sound immensely better than when i got them all the work was worth it .

Mark

 

[spkrdtr]

Rewinding inductors. Now that's dedication and persistance. Good job

 

[custino]

date of 2015 but I think L2 is not 2.1mh, but 0.8 mh maximum. it have not ferrit and with a little calcul, with dimensions, winding number and all the will of the world, L2 can't be a 2mh.
how did you mesure it ? on the pic your two L2 are out of service. So what inductance did you mesure ?


https://www.carnets-tsf.fr/inductance/calculateur.html


and be careful, L3 = 0,3mh... not 3mh


EDIT : ok I re checked winding number, and I was too just. possibly L2 is really 2 mh.

it should be same crossover than in the corelli, dn17 version, picture in this thread, second post :

https://www.ls3-5a-forum.com/viewtopic.php?f=21&t=7811&mobile=on
resistances in serie on self are resistance of the self.

too bad wire gauge of all these tiny kef coil are too little.
maybe a solution, to improve it : replace self by same value but more big wire, and make the complement value resistance of original self with a resistance.