Kef reference 107/2 recap

[andyrlb]

I thought I’d share this with those that may be considering recapping their reference speakers.
This morning I was looking forward to recapping the head unit of my 107/2’s , the only reason was that you read that capacitors have a 20 year maximum life.
Before replacing any I removed one and measured it , turns out it measured within its 2% tolerance and the new monacor replacement did not so I soldered the old one back in its place, tried a few more then eventually I tested all of the old ones and they ALL measured within their 2% tolerance, not bad after 25 years or more .
I will also add that when the Kef reference speakers were made the engineers were not able to obtain capacitors with exact values in the quantity they needed so each crossover would have their induction coils made by Kef to match the capacitor values being fitted , so the values written on the caps were not necessarily the true value, a record was made for each crossover/speaker which is why they are “ reference “ models , trouble is when Kef was sold the new owners destroyed all the records!!

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[Macca]

Why would they destroy all the records? Madness. I've worked places like that, stuff that really needs doing they put off forever but they can't wait to delete information or chuck stuff out and then of course the next day you need to refer to it, you can't, and it ends up costing them thousands. All for the sake of a few boxes in a cupboard or 1% of the space on a server.

[andyrlb]

Why would they destroy all the records? Madness. I've worked places like that, stuff that really needs doing they put off forever but they can't wait to delete information or chuck stuff out and then of course the next day you need to refer to it, you can't, and it ends up costing them thousands. All for the sake of a few boxes in a cupboard or 1% of the space on a server.

I agree mate it’s utter madness.
It’s reminded me of my first job at Hammond organs in Bletchley where I worked in their parts department and I was training to use the electric forklift, the guy training me turned out to be a raving lunatic ( he once drove a car at speed into lake ) he was also an alcoholic! He had showed me which large switch operated the forklift charger and explained that in the morning I must switch it to the off position before unplugging the forklift charger cable , thing is he thought it would be funny to show me the wrong switch! So I do as I’m told and switch off this big switch then I pull the plug on the forklift and off I go , around 10 minutes later I see the finance director approaching me and looking very angry, anyway the lunatic had shown me the mainframe computer switch and NOT the forklift charger switch so apparently I had lost them 3 months worth of accounts, I was sacked on the spot ! They then had my mother to deal with ( I was 16 years old)


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[Macca]

Christ that was bad. Fancy having the mainframe power where anyone could just turn it off.

Worked in a few warehouses and never met a fork-lift driver who wasn't a raving lunatic. I did it for a bit :D (well, low-loader but it's the same basic idea).

Having races around the floor when management weren't about. There was about ten pallets of yogurts stacked and the bloke in the proper forklift took a corner too fast and went into it, clipped the whole edge off of it. Then there was a yogurt fight in the remnants. The mess was incredible.

He held his hand up to it in the hope he'd get off lightly for confessing. But he didn't.

[walpurgis]

He held his hand up to it in the hope he'd get off lightly for confessing. But he didn't.

He broke one of the two golden rules. Deny everything. Never volunteer.

[Firebottle]

I once took out the whole power to where I was working. The computer bods were the most angry.

[andyrlb]

I once took out the whole power to where I was working. The computer bods were the most angry.

Glad it’s not just me [emoji23]


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[walpurgis]

I once took out the whole power to where I was working. The computer bods were the most angry.

I did the same. There weren't really any computers back then though. :)

[Macca]

Some spinning jennys went down though. :D

[walpurgis]

The water mill crashed too. :)

[Macca]

Unstable operating system.

[fatmarley]

Makes you wonder how many speakers out there have been recapped and sound worse for it.

[andyrlb]

Makes you wonder how many speakers out there have been recapped and sound worse for it.

Yes that’s what I thought, hopefully it just applies to the old Kef reference models , I’m still tempted to try one with new caps in it.


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[Lawrence001]

I was wondering if they've already been recapped by a previous owner hence your findings, but it's hard to get a definitive image of the original boards online, they might have been recapped before selling.

Incidentally, I found this video a wife made of her husband restoring their 104/2s. She says she really enjoyed the learning experience of soldering the second board herself. I must have word with my wife...

https://youtu.be/uAMvCsyZFaY

[andyrlb]

I was wondering if they've already been recapped by a previous owner hence your findings, but it's hard to get a definitive image of the original boards online, they might have been recapped before selling.

Incidentally, I found this video a wife made of her husband restoring their 104/2s. She says she really enjoyed the learning experience of soldering the second board herself. I must have word with my wife...

https://youtu.be/uAMvCsyZFaY

All the caps are original Kef marked caps and I can tell that all solder is original. My information came from an ex Kef engineer , it is a pain though that he has advised to not take notice of the marked values as it’s now impossible to know their original values albeit -/+ 2 % . Getting 2% caps now isn’t easy .


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[Beobloke]

Makes you wonder how many speakers out there have been recapped and sound worse for it.


As a former loudspeaker designer, it makes me wonder if this might make some forum "experts" (not AoS of course!) finally realise that most speaker designers aren't just charlatans who use any old shite components they have lying around in order to maximise profits...

[andyrlb]

As a former loudspeaker designer, it makes me wonder if this might make some forum "experts" (not AoS of course!) finally realise that most speaker designers aren't just charlatans who use any old shite components they have lying around in order to maximise profits...

I’ve no doubt that it happens and will continue to do so , it’ll probably get worse too !


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[sailor]

Hi Andrew, there is merit in replacing caps that are, in your case about 25 to 30 years old, with modern ones even if the original are still within spec. New caps do sound better and today there are lot more to choose from.

Consider that most speakers are built to a price point to be competitive in the market so understandably lower cost options are used. Perhaps 2000 pairs of a certain speaker are to be built and it uses 6 caps/pair at a cost of 6 pounds. To upgrade to some that cost say 40 pounds means an outlay of an extra 68000 pounds! Will probably not go down well with the accountant.

Try replacing just the caps in the tweeter circuit and while you're at it the attenuating resistors as well. The white sand cast jobs are nasty and replacing these with Mills will contribute to the improvement. I mention the tweeter because it usually has the lower value caps in circuit and therefore cheaper as an experiment.

You also get to slightly adjust the result regarding choice of cap. A Mundorf EVO in Oil is great value. It has a very slight tilt up in the extreme high frequency, or a neutral and smooth Clarity Cap CSA. I found the CSA to nicely reduce some sibilance while still remaining detailed. I mention Mundorf and Clarity Cap because I know them well but there are dozens to select from.

As you are only upgrading the tweeters on one pair of speakers it will not hurt your piggy bank too much and you will then hear for yourself what all the fuss is about.

https://www.hificollective.co.uk/catalog/-c-61_68_what all the fuss is abou429.html

[andyrlb]

Hi Andrew, there is merit in replacing caps that are, in your case about 25 to 30 years old, with modern ones even if the original are still within spec. New caps do sound better and today there are lot more to choose from.

Consider that most speakers are built to a price point to be competitive in the market so understandably lower cost options are used. Perhaps 2000 pairs of a certain speaker are to be built and it uses 6 caps/pair at a cost of 6 pounds. To upgrade to some that cost say 40 pounds means an outlay of an extra 68000 pounds! Will probably not go down well with the accountant.

Try replacing just the caps in the tweeter circuit and while you're at it the attenuating resistors as well. The white sand cast jobs are nasty and replacing these with Mills will contribute to the improvement. I mention the tweeter because it usually has the lower value caps in circuit and therefore cheaper as an experiment.

You also get to slightly adjust the result regarding choice of cap. A Mundorf EVO in Oil is great value. It has a very slight tilt up in the extreme high frequency, or a neutral and smooth Clarity Cap CSA. I found the CSA to nicely reduce some sibilance while still remaining detailed. I mention Mundorf and Clarity Cap because I know them well but there are dozens to select from.

As you are only upgrading the tweeters on one pair of speakers it will not hurt your piggy bank too much and you will then hear for yourself what all the fuss is about.

https://www.hificollective.co.uk/catalog/-c-61_68_what all the fuss is abou429.html

Thanks Charles , funny enough I spoke to Nick at Hifi collective and he too said to change the white ceramic components .

Cheers


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[Beobloke]

Personally, the resistors are the last things I would change.

If you really do have the urge to fiddle, then I agree that the component to experiment with are the capacitors in the tweeter circuit. These are directly in the signal path and so are likely to have a bigger effect than those in the midrange or bass circuits.

If it was me, though, I’d still leave them alone and enjoy them.

[Lawrence001]

I used to think that components not in the signal path didn't matter but then I had an idea. To oversimplify, it is that clean signal minus noisy signal equals noisy signal.

So whether the noise is generated by a component in the signal path, or the voltage difference between a clean signal and a noisy signal in a potential divider (ie parallel circuit) does it really matter?

Thoughts?

[sailor]

I have found that everything matters, even the manner of how the components are mounted. I stopped using cable ties a while back and now use Sikaflex (I prefer the 221) which is mostly found in the boat building industry and also to install vehicle windscreens. The patent Sika owned has now expired so there are a lot of similar products available at lower prices.

[andyrlb]

I have found that everything matters, even the manner of how the components are mounted. I stopped using cable ties a while back and now use Sikaflex (I prefer the 221) which is mostly found in the boat building industry and also to install vehicle windscreens. The patent Sika owned has now expired so there are a lot of similar products available at lower prices.

I use CT1 on a daily basis ( and silka products now and then ) .


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[Barry]

I used to think that components not in the signal path didn't matter but then I had an idea. To oversimplify, it is that clean signal minus noisy signal equals noisy signal.

So whether the noise is generated by a component in the signal path, or the voltage difference between a clean signal and a noisy signal in a potential divider (ie parallel circuit) does it really matter?

Thoughts?

It's a common misconception by those who do not understand electrical circuits, that the signal path runs through the centre of the circuit, and that only those components in series matter. As you have already noted, the signal is often relayed through a voltage divider which includes equally important shunt components.

Thus all parts of the circuit are to some extent part of the signal path; including the power supplies.