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Correction to split/moved thread

 
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speakerguru
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Joined: 18 Nov 2005
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Location: Green Hut, Tovil

PostPosted: Wed Jun 24, 2015 8:56 am    Post subject: Correction to split/moved thread Reply with quote

exkefman wrote:

The NT25s were also a bit more reliable, as initially some NT19's just "fell apart" as there was very little surface area for the glues (that held it together) to actually bond so well...but they got it right after a little while...remember this was all "cutting edge and new technology" at the time...and KEF was at the phase when it was just starting to use cyanoacrylate glues.


This is incorrect. KEF were using ca adhesives to stick rubber surrounds to chassis and voice coils to bextrene cones when I joined in 1975. NT tweeters were mid 80s.

The reason NT19s and NT25s "fell apart" was that Prod. dept. has not set up any humidity booths for the new production lines. CA adhesives do not cure if the humidity is too low. The poor operators were tearing their hair out producing failures when they knew full well what should have been done to fix the problem. I was sent to toubleshoot as I had designed both tweeters.
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Wiesiek Lipowski
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Joined: 10 Dec 2006
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Location: Poland

PostPosted: Wed Jun 24, 2015 3:32 pm    Post subject: Reply with quote

Are humidity packets inside the cabinets a good idea? I've got a DIY pair of Q55.2 and would like to save the tweeters.
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exkefman
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PostPosted: Wed Jun 24, 2015 4:29 pm    Post subject: Reply with quote

Wiesiek Lipowski wrote:
Are humidity packets inside the cabinets a good idea? I've got a DIY pair of Q55.2 and would like to save the tweeters.


Hi

There's no need, as we're talking about a production process and allowing the CA glues to "cure" on the very early Uni-Q tweeters.

I very much doubt that some silica gel bags will make any difference to later HF units long term usage or reliability
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Tim

(I used to work for KEF from 1988-1995 - you can see my "profile" here: http://www.hifiloudspeakers.info/speakertalk/viewtopic.php?t=1706)
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speakerguru
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PostPosted: Wed Jun 24, 2015 10:21 pm    Post subject: Reply with quote

Wiesiek Lipowski wrote:
Are humidity packets inside the cabinets a good idea? I've got a DIY pair of Q55.2 and would like to save the tweeters.

No. Water vapour is required for ca adhesives to cure in a reasonable time, after that they are stable. If humidity is low then the time to cure increases greatly and this is a problem for production with a limited number of assembly jigs and space to store units while they "set". Once cured, you don't need high humidity to maintain the bond.
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