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KEF 105.3 refoam and ferrofluid Cadmium washers?

 
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oldandintheway
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Joined: 16 Mar 2018
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PostPosted: Mon Aug 26, 2019 11:41 pm    Post subject: KEF 105.3 refoam and ferrofluid Cadmium washers? Reply with quote

So, just carried out a refoam and ferrofluid replacement on my lovely rosewood 105.3

When I removed the speaker pod at the front, there were four washers, they were corroded but they looked like cadmium coated washers - white powder is the corrosion by product. I cleaned it away and washed hands afterwards just in case. Does anyone know whether they were cadmium coated?

If so, we ought to warn people about it! It's pretty toxic, not just to people.
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speakerguru
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Joined: 18 Nov 2005
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Location: Green Hut, Tovil

PostPosted: Tue Aug 27, 2019 4:03 pm    Post subject: Reply with quote

Sorry can't remember definitively but the words "zinc plate, chrome passivate" seem to be lurking in the back of my brain for all KEF metalwork of that era. Could that be it?
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oldandintheway
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PostPosted: Wed Aug 28, 2019 9:09 am    Post subject: Reply with quote

That's probably it, although the passivation process isn't considered that safe anymore the corrosion by-products of an item such coated (white powder) 'shouldn't be too bad (obviously, don't lick!).

Cadmium coating would have been a very extreme measure for some washers used on home speakers!

Thanks for getting back to me.
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oldandintheway
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PostPosted: Thu Sep 12, 2019 10:25 pm    Post subject: Reply with quote

Another thing...behind one of the SP1240 tweeters, i noticed that there were two 'washers' behind it (the 'C' shaped ones with the hex centre) the other speaker had only one (as part of the main driver chassis to align and support the SP1240).

Were they used to space the SP1240 to the correct position to maintain phase relationship?

Or was it simply fitted by mistake?


Last edited by oldandintheway on Sat Sep 14, 2019 3:46 pm; edited 1 time in total
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speakerguru
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PostPosted: Fri Sep 13, 2019 9:00 am    Post subject: Reply with quote

oldandintheway wrote:
Were they used to space the SP1240 to the correct position to maintain phase relationship?

Or was it simply fitted by mistake?


No. You can calculate one washer's worth of phase shift assuming the the velocity of sound in air is 345m/s Laughing

Yes, a mistake.
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oldandintheway
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Joined: 16 Mar 2018
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PostPosted: Sat Sep 14, 2019 3:44 pm    Post subject: Reply with quote

Don't tempt me, i just might haha!

it was a quick job to remove, desolder and get rid of the 'spare' washer. I had the then check the other speaker, it had just the one fitted as part of the main driver chassis to support the SP1240. Normality has been restored.

Thanks for the insight.
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