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RR105-3
Intermediate Contributor 25+
Joined: 13 Jul 2007
Posts: 29
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 Posted: Wed Jun 24, 2020 3:38 pm Post subject: Tweeter replacment NT25 KEF 105/3 |
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in the search for replacement units for my KEF 105/3 tweeters NT25's, I was offered the SP1628, are these useful types as a replacement?
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history: 1978 RR104ab /1984 RR104-2 /1990 RR105-3
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in my posession at this moment -
RR105-3 / RR104ab / C95 / C75 / C60 / C10 / Chorale / Cresta 1970 / Corelli / |
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speakerguru
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Joined: 18 Nov 2005
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Location: Green Hut, Tovil
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| Posted: Wed Jun 24, 2020 5:39 pm Post subject: |
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| SP1628? Can't say it rings any bells. Where is it on offer? Do you have any pictures? |
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RR105-3
Intermediate Contributor 25+
Joined: 13 Jul 2007
Posts: 29
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| Posted: Wed Jun 24, 2020 6:54 pm Post subject: |
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| speakerguru wrote: | | SP1628? Can't say it rings any bells. Where is it on offer? Do you have any pictures? |
the SP1628 is a 4Ohm, 25mm unit, and with some work (ripping of the plastic housing) it wil probaly fit physical.
its offered to me by a well known respectable audio-repair company here in the Netherlands . it has the looks of the tweeters used by KEF today
question is, wil it be a good sonical match in a RR105-3 ?
_________________
history: 1978 RR104ab /1984 RR104-2 /1990 RR105-3
-------------------------------------------
in my posession at this moment -
RR105-3 / RR104ab / C95 / C75 / C60 / C10 / Chorale / Cresta 1970 / Corelli /
Last edited by RR105-3 on Tue Jul 07, 2020 1:56 pm; edited 2 times in total |
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speakerguru
Über Contributor 1000+
Joined: 18 Nov 2005
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Location: Green Hut, Tovil
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| Posted: Thu Jun 25, 2020 5:03 pm Post subject: |
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Is Transtec still the dutch KEF distributor? I guess they have a supply of service replacements for the current KEF Uni-Q.
Other than the magnet assembly, I know next to nothing about the current Uni-Q drivers. I would think that being metal dome, the tweeters are significantly different in acoustic response compared to the older cloth dome T33s. The on and off axis response will undoubtedly depend on the combination of XO eq, the protective grid and the woofer cone shape. Without acoustic measuring equipment it will be impossible to say how close the response would be if used to replace the old T33 in an older system. OTOH, if you have no alternative and can live with non-reference series response limits then there is little to lose in trying it. The sensitivity. at least, may well be in the right ball park. |
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RR105-3
Intermediate Contributor 25+
Joined: 13 Jul 2007
Posts: 29
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| Posted: Thu Jun 25, 2020 11:07 pm Post subject: |
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| speakerguru wrote: | Is Transtec still the dutch KEF distributor? I guess they have a supply of service replacements for the current KEF Uni-Q.
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thank you for the response
No, Transtec is not the KEF distributor anymore )-;
plan A is to do a cleanup/ferrofluid refill on the original NT25's in my 105/3's
waiting until they stop working is a unnessecarry risk.
(Raymond Cooke will turn in his grave if I kill these RR105-3 without trying not to save the original design  )
I do have some experience with taking out a set NT25's from a pair C75's
Where to order/buy the FerrorFluid will be the first challenge...
And these SP1628's will probaly be placed in the C75's, just curious how this will match/sound.
_________________
history: 1978 RR104ab /1984 RR104-2 /1990 RR105-3
-------------------------------------------
in my posession at this moment -
RR105-3 / RR104ab / C95 / C75 / C60 / C10 / Chorale / Cresta 1970 / Corelli / |
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RR105-3
Intermediate Contributor 25+
Joined: 13 Jul 2007
Posts: 29
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speakerguru
Über Contributor 1000+
Joined: 18 Nov 2005
Posts: 1192
Location: Green Hut, Tovil
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| Posted: Mon Jun 29, 2020 12:22 pm Post subject: |
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| 80cp as opposed to the 75cp of the original APG512 sounds close enough to me. Very reasonable price too. Good find! |
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RR105-3
Intermediate Contributor 25+
Joined: 13 Jul 2007
Posts: 29
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| Posted: Mon Jun 29, 2020 1:34 pm Post subject: |
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| speakerguru wrote: | | 80cp as opposed to the 75cp of the original APG512 sounds close enough to me. Very reasonable price too. Good find! |
thank you for the response,
this German side has a lot "magnetic" stuff, very handy.
Next to the Ferrofluid I also orderd Self-adhesive neodymium magnets for mounting a set of "future DIY " new grills for my 104ab's
update 02 June
FerroFluid arrived today
_________________
history: 1978 RR104ab /1984 RR104-2 /1990 RR105-3
-------------------------------------------
in my posession at this moment -
RR105-3 / RR104ab / C95 / C75 / C60 / C10 / Chorale / Cresta 1970 / Corelli /
Last edited by RR105-3 on Thu Jul 02, 2020 10:55 am; edited 1 time in total |
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RR105-3
Intermediate Contributor 25+
Joined: 13 Jul 2007
Posts: 29
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| Posted: Wed Jul 01, 2020 11:01 am Post subject: The SP1628 is a perfect replacement for the NT25/SP1240 |
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today I replaced the NT25 tweeter in my KEF C75 with a modern 25mm 4Ohm tweeter from KEF the SP1628.
to build in the SP2628 I only needed an approximately 4 cm long 4mm bolt
I used a suitable bolt i found in my old constructor/Mecano kit
I was wondering if this job would be easy, in preparation for face-lifting my RR105-3 tweeters. and yes on the C75 it was a easy job
the result is excellent, the C75 is completely fresh and fruity again.
here a impression, made with my smartphone, to give you an idea :
https://youtu.be/t79uhTbla6M
The SP1628 is a perfect replacement for the NT15/SP1240 !
see the photos for the old_new version of a reborn C75.
sounds great.
next week I will tackle the 105-3, I will consider whether I refresh the NT25 with new FerroFluid. or that these SP1628 will end up in the RR105.
work in progress ...
Oh. until today my C75 had a another "C75 unworthy" embarrassing DIY
"chinese" low cost 4Ohm tweeter replacement which also worked good ...
see picture below...
_________________
history: 1978 RR104ab /1984 RR104-2 /1990 RR105-3
-------------------------------------------
in my posession at this moment -
RR105-3 / RR104ab / C95 / C75 / C60 / C10 / Chorale / Cresta 1970 / Corelli /
Last edited by RR105-3 on Wed Jul 08, 2020 12:56 pm; edited 1 time in total |
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RR105-3
Intermediate Contributor 25+
Joined: 13 Jul 2007
Posts: 29
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| Posted: Tue Jul 07, 2020 1:59 pm Post subject: NT25 drama |
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Yesterday I removed the NT25 from 1 RR105-3 for a ferrofluid refill, loosening the PCP from the diaphragm became a disaster, the coil was stuck in the air gap, and came off the diaphragm .... and also the wires broke .. ..
so I replaced it with the one spare NT25 that I had from a C75.
situation now:
1 pair of RR105-3 working, 1 with an new Ferrorfluid refilled NT25 from the C75, and 1 with the original unit (sounds ok),
1 pair of C75 working fine with the SP1628 tweeters.
this week I'm going to pick up a a pair C95 with dead tweets, hoping to get the NT25s back to work.
in the worst case, the modern SP1628 \s will go into the 105-3 , the working NT25s will go into the C95, and 2 chinese aliexpress 4Ohm tweeters will end up in the C75
_________________
history: 1978 RR104ab /1984 RR104-2 /1990 RR105-3
-------------------------------------------
in my posession at this moment -
RR105-3 / RR104ab / C95 / C75 / C60 / C10 / Chorale / Cresta 1970 / Corelli /
Last edited by RR105-3 on Tue Jul 07, 2020 7:02 pm; edited 1 time in total |
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speakerguru
Über Contributor 1000+
Joined: 18 Nov 2005
Posts: 1192
Location: Green Hut, Tovil
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| Posted: Tue Jul 07, 2020 4:24 pm Post subject: |
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| I'll have a deep excavation of my garage, when the mood takes me. I'm sure there are some tweeters in there somewhere. If I do find some, I wonder what state the ff would be in after years of storage unused? |
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RR105-3
Intermediate Contributor 25+
Joined: 13 Jul 2007
Posts: 29
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| Posted: Tue Jul 07, 2020 6:57 pm Post subject: |
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| speakerguru wrote: | | I'll have a deep excavation of my garage, when the mood takes me. I'm sure there are some tweeters in there somewhere. If I do find some, I wonder what state the ff would be in after years of storage unused? |
The NT25's that came out of the C75 almost fell apart by themselves, the NT25 out of my 105-3 was different , it was hard to remove the PCB from the metal magnet. the coil was trapped in the aircap in a kind of rubber residue, the dried up FerroFluid. ended up with a separate coil and dome-conus
i think probaly a good/better way to open up a NT25 is to open it up on one side 1mm, and then inject alcohol to dissolve soften the rubber residu in the aircap, and then gently separate the PCB/tweetercoil from the iron/magneet
the 105-3 NT25 had a serilal number, and the twosided thin gluetape was visable, this was not the case with the "default" C75 NT25
_________________
history: 1978 RR104ab /1984 RR104-2 /1990 RR105-3
-------------------------------------------
in my posession at this moment -
RR105-3 / RR104ab / C95 / C75 / C60 / C10 / Chorale / Cresta 1970 / Corelli / |
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RR105-3
Intermediate Contributor 25+
Joined: 13 Jul 2007
Posts: 29
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| Posted: Tue Jul 28, 2020 7:24 pm Post subject: |
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| RR105-3 wrote: | | speakerguru wrote: | | I'll have a deep excavation of my garage, when the mood takes me. I'm sure there are some tweeters in there somewhere. If I do find some, I wonder what state the ff would be in after years of storage unused? |
The NT25's that came out of the C75 almost fell apart by themselves, the NT25 out of my 105-3 was different , it was hard to remove the PCB from the metal magnet. the coil was trapped in the aircap in a kind of rubber residue, the dried up FerroFluid. ended up with a separate coil and dome-conus
i think probaly a good/better way to open up a NT25 is to open it up on one side 1mm, and then inject alcohol to dissolve soften the rubber residu in the aircap, and then gently separate the PCB/tweetercoil from the iron/magneet
the 105-3 NT25 had a serilal number, and the twosided thin gluetape was visable, this was not the case with the "default" C75 NT25 |
_________________
history: 1978 RR104ab /1984 RR104-2 /1990 RR105-3
-------------------------------------------
in my posession at this moment -
RR105-3 / RR104ab / C95 / C75 / C60 / C10 / Chorale / Cresta 1970 / Corelli / |
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RR105-3
Intermediate Contributor 25+
Joined: 13 Jul 2007
Posts: 29
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| Posted: Wed Jul 29, 2020 10:24 am Post subject: Ferrofluid and NT25 .... here is what you can do ... |
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yesterday I bought a very nice mind set C95's on ebay for only 100 euro , both speakers with working but dull NT25 tweeters, today the 2 tweeters are cleaned and filled with new ferroFluid, and now they really play like new .... I'm happy!
splitting the tweeters open was exciting, because they were stuck in the air gap, first carefully pry the pcb max 1mm open from the magnet ,
(be careful not to far away, you can ripp the coil off from the diagram !!))
to make a "gentlle controlled" first little cap, see how I did this:
do not tap to hard!
https://youtu.be/2J2Xwbj1pNA
then let some alcohol run into the 1mm gap between pcb and magnet to dissolve the olf ferrofluid to loosen the coil from the air-cap, then gently turn the pcb back and forth (max 1 mm !!!) until there is some movement, then gently pull the VC out of the aircap (let the alcohol do his job voor 30 seconds, if necessary add some more alcohol) BUT DO THIS ALL VERY VERY VERY GENTLY !
here some picture's of the new couple !
_________________
history: 1978 RR104ab /1984 RR104-2 /1990 RR105-3
-------------------------------------------
in my posession at this moment -
RR105-3 / RR104ab / C95 / C75 / C60 / C10 / Chorale / Cresta 1970 / Corelli /
Last edited by RR105-3 on Mon Oct 05, 2020 2:29 pm; edited 1 time in total |
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oldandintheway
Intermediate Contributor 25+
Joined: 16 Mar 2018
Posts: 32
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| Posted: Fri Sep 04, 2020 1:13 pm Post subject: |
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| That's brilliant work RR105-3,would you say the SP1628 is an acceptable replacement for the SP1240 sound wise? +1 on the ferrofluid find/source! |
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