Kef Reference Tweeters-Ferrofluid Replacement



It took me three months to build up the courage to replace the Ferrofluid oil in my Kef tweeters.
There were several good videos on the internet how to go through the process, one in particular out of Texas. 
There were no videos or instructions which directly related to my specific speakers; Reference 3~2.
They are ~ 20 years old and I noticed that the highs were muddy and dull in the right speaker.
I run a Cardas Frequency Sweep record every 6 months or so.  The tweeter issue was noticeable during this maintenance procedure.
No replacement speakers (tweeters) are available from Kef or anywhere on the internet, so one wrong move and the speaker system would be worthless.  I felt like I was performing brain surgery.

First speaker took ~ 3 hours.  Second about 30 minutes.
I am happy to announce that the 'oil change' was successful!
The speakers are back to full factory operating specifications.
I've attached a link with some photos below.
If anyone needs to perform this procedure I can help walk you through the process.

Take care,
Lou
https://photos.app.goo.gl/qt1ZUPk8jF1QNkUu6

quincy
"No replacement speakers (tweeters) are available from Kef or anywhere on the internet".
This is a warning to current owners.

1. Do your tweeters use ferro-fluid?
2. Are replacements currently available?
3. Are you planning to keep your speakers a long time?

If you answered "Yes" to all three, might want to get those replacements now while you can!
A timely post for me. I have KEF Reference Model Ones and will shortly be replacing the ferrofluid in them. I did the ferrofluid in my KEF 104/2s previously and it was a very simple job. Took about 30 minutes for each tweeter. The Reference Model Ones seem a bit more complicated in getting the tweeter out. 
A couple of questions for Lou:

Does the NT25 tweeter just come out from the back side of the midrange driver assembly after removing that one screw in your photos?

Was the voice coil diaphragm attached to the magnet with an adhesive? If so, what adhesive did you use to reattach them?
Kef Reference only guarantees replacement parts for 10 years, fortunately their drivers, all in house are robust. My R105/3, were regularly run at 104 db and in 25 years never failed, well 1 did by OE no fault of kef.
ljgerens,

The tweeter needs to be gently pushed out forward from the mid range speaker once you pull the screw and rubber washer out.  Use a 1/4 drive extension about 6" long.  You will need to un-solder the small, thin wires first or the tweeter will not come out far enough to work on it.  Purchase a small electronic soldering iron for this purpose.  Use a pair of small electronic needle nose pliers to help get the wires out once you melt the solder.

Carefully remove the tweeter dust cover using a 'eye glass' flat bladed screw driver.  There are 2 small gaps for this purpose.  The voice coil is right under this 'cap'.  The voice coil is actually immersed into the Ferrofluid.  It sits into the groove annulus of the tweeter.  So, I can now understand how this system works.  The Ferrofluid is used as a lubricant and coolant for the operation of the voice coil.   I'm not 100% certain, but I believe the voice coil dithers up and down some how in this groove to create the high frequency. 

Use great caution.  Everything is very fragile!  Good luck!  Let me know how you make out.   
Awesome!  Thanks for posting.  This has been something thats been coming up with me lately.  Many speakers I’ve been interested in lately would probably benefit from this procedure.  Good to knoW that it isn’t too too dificult
OP - Did you have to clean the old fluid off the voice coil first? If so, how?
Thanks
Lou,

Thanks for the info. Was there any adhesive holding the voice coil diaphragm to the magnet. On the T33 tweeters in my KEF 104/2s they had a thick double sided tape holding them together and it was reusable.
Dweller,
The voice coil sits in the fluid.  
Yes, I cleaned it.
Q-Tip with rubbing alcohol in a circular motion.  Very gentle!
Both inside and outside diameter was cleaned.

lljgerens,
I did not remove the voice coil entirely from the speaker body.  Enough slack is avail in the wires to lift it out an off and to one side.  See photo.
hi, Lou
thanks for the interesting and necessary topic you created!
I needs to perform procedure of Replacement Tweeters-Ferrofluid in my Kef Reference two - two (almost the same as yours 3-2)!
can you help me to walk through this the process?
now question number one and basic:
how to remove the front black plate to get to the midrange and tweeter speakers? i need to extract this speaker!
on your first photo (by link) the speakers are already without the black front plate.
Thanks!
Regards, Alex
Enter your text ...
Hello Alex,
I will try my best to assist you in your rebuild of your Kef speakers.
The black plastic 'diffuser'  (not sure what it is called) is held on with Allen head hex screws.  Six each speaker in my case.  Borrow or purchase a inexpensive set for this process step.  It has to come off, you can't get to the speakers with it in place.  I had 6 plastic plugs that were in front of (on top of) the allen hex screws.  I saw no purpose to these 'plastic plugs' other than to confuse you about the disassembly process.  I did put them back because, well, you just never know.....  You can get the plugs out by jamming a phillips head screwdriver into them and rotating counter clockwise.  These plugs are not attached to anything, only a press fit.  I often wonder how many folks stopped at this stage because of the confusion created.  No written or visual instructions exist, that I could find anyway.  That's why the first speaker took me 3 hours of 'discovery'.
Hi Lou,
Thank you very much for your prompt reply.
I have already solved this problem with this video from the audio forum (post 114)
who would have thought of these plastic plugs !!!
I broke my whole brain how to do it, but I was sure that it could not be very difficult :) ...
I will move on to the next stage ...
good luck
best regards Alex
https://audiokarma.org/forums/index.php?threads/kef-nt25-tweeter-refurbishing-with-pictures-and-a-question.709897/page-6
Post removed 
Okay Alex,

Any thing else just ask away.

Don't know if its possible, but if you send a pm, I'll supply my phone number and try to help that way if you wish.

Good luck!
Lou
Hi Lou,
How many packs of ferofluid APG L11 100ul for the two tweeters did you use?
is one package enough?
Thanks!
Regards, Alex
Yes, same place I purchased mine!

I had no idea how many or how much when I did mine.
I bought six, used two.

So, to answer your question, one packet per tweeter.

Its amazing stuff.  The tweeter magnet just grabs the ferrofluid and it distributes itself around the entire annulus via magnetism.

Don't forget to clean off your voice coil with q-tips saturated with rubbing alcohol.   You need to get all the old gunk off.  Be gentle!

I’ve been telling the older Thiel owners this for years now, when they all started complaining about harsh highs.
It’s just the Ferofluid drying out and turning into thick paste and making the voice coil bind in the magnet gap, causing non linear distortion, and it can cause overheating as well. 
Do a search, there's even better instruction with the links I posted in those Thiel threads.

Cheers George
Alex,
For 1 inch tweeters, you only need one 100ul tube for each tweeter. I purchased 2 tubes from Parts Express for my KEF 104/2s which have 1 inch tweeters. 
Thanks for the additional info and support guys!
Lou
I posted the Ref 2 video that is mentioned above. If you have any questions about the process of getting the tweeter out, let me know. I did send in the tweeter to an authorized Kef repair center for the ferrofluid replacement.
Please post the contact information for others in regards to the company authorized to work on Kef equipment.  Phone, e-mail address, etc.

Good luck reassembling everything!

Thanks,
Lou