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Crossover Documentation

 
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crdm6
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Joined: 21 Jan 2020
Posts: 8
Location: Puget Sound

PostPosted: Sun Jan 26, 2020 7:16 pm    Post subject: Crossover Documentation Reply with quote

Since KEF actually measured all the parts in the crossovers and kept records of what the values actually were not what it said on them, would it be a good idea for me to measure the values of the caps in my Reference 102s before they have a chance to drift?
They weren't made yesterday so this is assuming they're still good.
I thought it might be a good idea for future preservation since they were part of the "Reference" series they would of a higher precision.
Am I being OCD about this or does their sound REALLY depend on the crossover's precision?

Thanks
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speakerguru
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Joined: 18 Nov 2005
Posts: 1037
Location: Green Hut, Tovil

PostPosted: Mon Jan 27, 2020 2:02 pm    Post subject: Reply with quote

A bit OCD, a bit late but better than nothing I suppose. Laughing

The Cs will have most likely have drifted in value and increased in loss factor after ~40 years.

I personally wouldn't worry about it until some thing audibly stops working.
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crdm6
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Location: Puget Sound

PostPosted: Mon Jan 27, 2020 6:51 pm    Post subject: Reply with quote

For some reason I didn't think of them as 40 years old probably because now days a 6.5" woofer and a dome tweeter is so common. It wasn't back then. You're right the train has left on getting original values on the caps. I was going to open them up for some cabinet refurb but I guess I'll redo the crossovers as well. I'll still measure them all.

I don't suppose anyone has any old documentation on the caps KEF used?

It is a bit OCD but it makes me crazy when people say "Sure, that'll work. The tolerance is +/- 10%".

If the values are +/- 0.1% and pair matched, I don't have to wonder if I can hear it.
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SaSi
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Joined: 24 Aug 2008
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PostPosted: Sat Feb 22, 2020 6:35 pm    Post subject: Reply with quote

The way matching seems to have been with reference speakers in KEF is to separate components in tolerance ranges and then mix and match various ranges of each component together to cancel out each other's effect.

Not sure whether the drivers themselves were included in the mix'n'match algorithm, but they should probably be.

What I'm going to is that it's pretty much impossible to re-create something like the original today. And the capacitors are most likely drifted already.

And then there are the drivers themselves. Haven't they deteriorated mechanically at least a bit?

I would simply recap using tight tolerance (5%) capacitors and call it a day. It will be a vast improvement against drifting values in the crossover and probably 98% of the original target.
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