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—more on why that might be significant shortly. 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 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 sits 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.
I suspect that years ago, with his hearing already failing, the voice coil burnt without him noticing. Continuing to play them, 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 an ex-KEF employee in a forum I stumbled upon stated that the diameter of the voice coil in this kit is too small (2.006" instead of 2.040") and that it'd be near impossible to fit it correctly. Anyone know anything 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
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—more on why that might be significant shortly. 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 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 sits 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.
I suspect that years ago, with his hearing already failing, the voice coil burnt without him noticing. Continuing to play them, 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 an ex-KEF employee in a forum I stumbled upon stated that the diameter of the voice coil in this kit is too small (2.006" instead of 2.040") and that it'd be near impossible to fit it correctly. Anyone know anything 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
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