KEF 107s - Looks like a new project... - diyAudio
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Old 8th December 2013, 06:57 PM   #1
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Default KEF 107s - Looks like a new project...

I recently came across a pair of KEF 107s, free. Yea! Unfortunately, they lacked tremendously of bass. I read a lot about the KUBE, which is missing, and thought that might solve the issue. But, after some close listening, I realized that the woofers were not working at all. So, decided to start disassembling and see what was up.

Immediately, I could tell by the condition of the screw heads that these had been worked on before. Nevermind that, screws are easy to replace. Looking at the crossover, it has been modified, and poorly. (Pictures below) A replacement coil was added, but was too large for the board. Whoever did this used a smaller gage of wire and ran double strands, and then soldered them to the board (extremely poorly) instead of using disconnects. There is a strong potential for contact between the posts. Also, four capacitors were piggy backed. And, the woofer foam is now past tense. All pictures are from one speaker. I have not fully opened up the other, but quickly looked at the crossover. Same story, but additional issue in that the two wires coming of the new coil contact each other.

I'm thinking about rebuilding the crossovers. But, I get the feeling that the woofers in these might not be original (thus the need for modifications to the crossover?). Can anybody tell by the picture?

If these aren't the original woofers, maybe I should just part these out. But, a rebuild would be a fun winter project. Just not sure if I can't find all the crossover components that will be needed. Also, need to learn about refoaming the woofers.

Any thoughts on what to do next?

Thanks,
Ridge
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Old 8th December 2013, 08:31 PM   #2
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The woofers look pretty original to me.
The foam surround where a dust cap would normally be found is a bit of a giveaway on these.

It looks like a nice little project.
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Old 8th December 2013, 08:44 PM   #3
Eldam is offline Eldam  France
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Location: At home, sweet sound home...
BEAUTIFULL PROJECT.... I'm jealous !

Assuming it's the first 107 : 1986 to 1989 :

tweeter is T33 sp1210 4 ohms (I love it in my kef 104/2 first serie)
Mid is B110B sp1209 4 ohms (Like the warm bextrene cones)
Bass is B300B sp1071 8 ohms? Have a doubt here...

Maybe the second 107, 107/2 has rubber instead foam in bass drivers... maybe with the serie number of the speakers you can ask to kef a pair of spares with the genuine concistency (not sure it's important for the bass cabinets).

Give up the Solen. Not sure the white Multicap (or MIT) was original with the XO ?! sad for the self coil, because if I remember the XO of the ref serie was made with less 2% tolerance... (like the drivers spares Kef kept for repair)

Last edited by Eldam; 8th December 2013 at 08:49 PM.
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Old 9th December 2013, 07:20 PM   #4
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Kept working on it after the original posting. Got the bass drivers out, and according to the tags, they are B250s.

Pretty sure these are 107/2s, at least from my initial study months ago.

All in all, I think I can re-foam the woofers, re-wire (adding some disconnects), and give it a test drive.

But I'm a little nervous about the XO. I'm stumped on what the modifications were for, plus after seeing some pics online of the original XO, many of the caps are the wrong ones, nevermind the piggy backs. The modifications are also not consistent between each speaker. I could replace all the caps, but not sure where to find the coil. Perhaps that's where the POs modifications began....

Anybody have specs or a source for new coils?
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Old 9th December 2013, 07:43 PM   #5
DrBoar is offline DrBoar  Sweden
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The vintage KEF web site Home Page hifiloudspeakers.info
Should have some info or at least people in the forum that knows
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Old 19th December 2013, 09:43 PM   #6
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I refoamed the first speaker, cleaned up the soldering and replaced some wires. Put it all back together and it works great. Added a subwoofer amp to help out the low end since I don't have a KUBE. Works even better! Really happy with it.

I now have the second one apart, and the woofers cleaned up and ready for refoaming and installation. Ran into a snag, though. The terminal on one woofer was broken in half, so I got a blank PCB from Radio Shack and cut it to size. Made a replacement and installed. Was quite proud of that little job until I notice that the lead tinsel was also disconnected from the speaker. See photo.

Looks like it is simply glued on... but that surprises me. Any suggestions on a repair?

Thanks,
Ridge
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