SpeakerTalk

[Huba Buba]

Hi everyone,

I am currently in the process of restoring a pair of KEF 107s, complete with the original matching KUBE. They had a single previous owner who took good care of them, a retired sound engineer with a severely failing hearing. Talking to him about them, he explained that the head assembly with the mid drivers and tweeters worked perfectly, but that he hadn't used them for years and that the woofers would probably need refoaming. As expected.

Upon arriving home, and more careful testing, the mids and highs seemed flawless, but I noticed some light distortion from the left bass cabinet. Turning the volume up a little produced buzzing and light distortion from both cabinets. Surely the surrounds were all gone. I ordered a refoaming kit, and started prepping everything. I bought new ferrofluid for the tweeters too while at it.

Taking the drivers out, three of them had completely disintegrated surrounds, but on one they were more or less intact, although quite cracked. Sitting down with the drivers to start stripping them of glue and residue, the driver with the surrounds still on revealed a potentially big problem. The voice coil had burnt through the paper tube it is wound on, and made a tangle of burnt copper wire in the little circular space beneath the donut. I also noticed that the cone was protruding beyond the frame, and the spider seemed to be bulging.

One possible (?) hypothesis is that years ago, with his hearing already failing, the voice coil burnt without him noticing. Continuing to play the speakers, the mechanical motion caused the coil wire to tangle up, thereby seizing the woofer and preserving the surrounds on that particular driver.

Two drivers seem fine, with resistance readings of about 7Ω (they're rated at 8Ω, so that's acceptable/normal (?)). One driver reads 15Ω, and the one with the burnt coil reads 4Ω. Any insights into these readings?

I've looked at the reconing kit from The Speaker Exchange (https://reconingspeakers.com/product/kef-sp1215-10-aftermarket-recone-kit-kef-107-b250/), but according to this post (http://www.hifiloudspeakers.info/speakertalk/viewtopic.php?t=1917) the diameter of the voice coil in this kit is too small (2.006" instead of 2.040") and it'd be near impossible to fit it correctly. The info text does state that "This kit requires some modifications!", although I don't know exactly what that means. I have contacted them about this, but have not heard back yet. Does anyone have more information about this?

Another option is having the driver professionally reconed/rebuilt, but I wouldn't know where.

Lastly, I could look for a replacement driver, but the KEF B250 seems very difficult to obtain.

To sum it up, I now have an issue on my hands that I hope someone could help me figure out. Any advice would be massively appreciated!

All the best,
- Kristoffer

[Huba Buba]

Update:

The Speaker Exchange got back to me regarding the stated modification requirements of the reconing kit:

[ebf]

I ordered the kit. They sent me the wrong parts! They have re-sent it, but I have not yet received it. I live in Norway. I have now 7 spare B250s, but at least 4 need new coils (I ordered 4 kits).
So I dont know yet if they fit. They have sent me pictures of them re-coning, and it seems OK.

But yeah, ordering from the US and having them ship to NO, has taken me 6-10 weeks now in the covid19 times...

Patience!

E

[speakerguru]

[Huba Buba]

Hi everyone,

Thanks for your replies! I still haven't made any move with this project, as I'm still trying to navigate the options.

Also very interested to hear your experience with the reconing kit when you receive the correct parts, ebf!

All the best,
- K

[Derekdick]

Hi I just purchased a pair of KEF 107s with a KUBE.
Looks like the vendor was the type that buys and sells old equipment. Says they refoamed the woofers. Says they got them from the one original owner.

As I am using a NAIM amp and pre-amp I am having to wait on the arrival of new cables to connect the KUBE to the proprietary sockets that NAIM uses, 4 pin to dual RCA and back again.
Speakers are running well so far, and they sounded good when auditioned, but hoping I will get a little more bass when I get the KUBE installed.

Anyway, "restoration" questions, as this is what this thread is about.
I have ordered ferrofluid for the tweeters, thought it was going to be fairly simple as I watched a Youtube video on replacing the fluid, then I see that maybe the cabinet on the mid and tweerer does not just fall apart when the screws are removed -so how do I get the tweeters out - will all become clear once I start?
The other big questions is where do I buy grille cloth? There is a small hole on one grille, front corner, - it looks like the material is stretched over fours side of the cube - is there a recommended supplier of material that stretches that much with no wrinkles?

Happy to be a member of the KEF Owner's Club at last

[ebf]

First off, I dont think you EVER need to take apart the heads.

Unscrew the tweeter and midrange and you should be all good.

For parts, mostly Falcon Acoustics is a good source, maybe even for grill cloth.

[Derekdick]

Indeed, on examination, the speakers just unscrew from the front.

Grill cloth is more of an issue, with the need to cover a cube with no seams, rather than the usual flat speaker covers. Obtaining something stretchy enough would be the concern, so if anyone has bought, and the same material is still available, then that would be good.
The eBay sellers often seem to be sold out before they respond to a question, or they are not really going to know if the material is pliable enough, and nor will I until I order a lot and try fitting it.
There is no rush, this can wait until more info is obtained.