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Ah crap.. right Kef 104/2 tweeter is distorting!

canuckaudiog

canuckaudiog

On a quest for high fidelity
Well, it finally happened to me. My T33 in my right Kef 104/2 started to distort, almost sounding like it was blown.

Now, it's well known that these tweeters use ferro fluid in the magnet gap to increase power handling and to reduce heat to the voice coil. I have no idea if this makes it actually sound better. Anyway, so I'm playing Bioshock and the right tweeter is most definitely distorting. Ah crap I think to myself, did the ferro fluid harden and ruin the tweeter?

Off with your head, Kef 104/2! Or more specifically, the front midrange/tweeter enclosure. I unscrew the 4 allen screws, pop it off, unwire it from the little PCB going to the internal crossover, and off it comes. Then it's just as simple as unscrewing the long screw that holds the tweeter in place, and that slides out of the way and the tweeter comes out.

Whew. That was refreshingly easy. All right, now I have to get the coil out of the magnet. Hmm.. well, let's test the tweeter as it stands right now. I get 10ohms.. that's not a good sign. OK, let's just get the coil out of the magnet and test it that way. The way it's held on is with a little piece of paper between the plastic baffle with the dome and the magnet. I had to pry this off very gently starting with one of the corners where the coil wire lead wires into. I say very gently because being plastic, putting too much pressure on one side could very well lead to it breaking. No thanks! With a little prying and time, the baffle comes off. I break out the meter and am now getting 5.8ohms! Ah, that sounds more realistic for a 6ohm tweeter. Nothing looks amiss on the actual coil itself or any of the lead wires, so getting a regular reading makes sense to me. This leads me to think the ferro fluid is somehow increasing the resistance of the coil and causing other fun stuff.

The next step now is to clean out the ferro fluid and see how the tweeter performs without it. Well, this is a bit of a rudimentary method but, I took some paper, and stuffed it into the gap and just kept wrapping it around in there until the paper started coming out clean. Not the, ahem, best way to do it but it worked. OK so now, the real test. I put the diaphragm back onto the magnet (which was simple by the way), put it all together and fired up some music.

Well now. This sounds much better! I did a comparison to the left speaker which still has the ferro fluid and no doubt about it, it now sounds rather dark and a bit midrange strong. Huh. Well, without the ferro fluid in there it's definitely going to cause the tweeter to handle less power, but as long as I'm very careful, I think it should be okay for now until I can source some proper ferro fluid.

The reason I am putting this up is because I know there are many of you whom have Kef speakers with the T33. I think it's imperative to get this ferro fluid changed, there's absolutely no doubt about it. It's as imperative as recapping the speakers. However the tweeter is more important because, if the ferro fluid hardens enough it could actually separate the coil. Not good. For those of you out there who have this tweeter in your speakers, I highly recommend at least cleaning out the ferro fluid and being very liberal with the volume until you can get some proper ferro fluid. I think having no ferro fluid is a better situation than having the goop harden up and ruin a tweeter.

If anyone has any details to add, please feel free, but I think this is the best bet until a solid solution (actually, not so solid in reality :) ) can be figured out.
 
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Bioshock Infinite?


Plus, I would probably just replace the tweeter now, unless you think you can replace the ferrofluid.
 
burgerbob said:
Bioshock Infinite?


Plus, I would probably just replace the tweeter now, unless you think you can replace the ferrofluid.
Click to expand...

I'm fairly certain I can replace the ferro fluid, it's just a matter of finding the right stuff. Replacing the tweeter is an option but, not one I want to explore.

And yes, Bioshock Infinite.
 
Geez... do I have to say this? ;)

:worthless

How are we going to rebuild our tweeters if we don't have any pictures! :scratch2:
 
canuckaudiog said:
I'm fairly certain I can replace the ferro fluid, it's just a matter of finding the right stuff. Replacing the tweeter is an option but, not one I want to explore.

And yes, Bioshock Infinite.
Click to expand...

Great posts. I had no idea ferro fluid was replaceable by the end user. Wonderful speakers BTW.
 
SimplySound said:
Geez... do I have to say this? ;)

:worthless

How are we going to rebuild our tweeters if we don't have any pictures! :scratch2:
Click to expand...

I'm gonna clean out the other tweeter tonight so, I'll snap some shots of it so you can see what it looks like. It's so easy to do though, so if anyone is following what I wrote you will see what I mean.

Next step I think now is to get at the crossovers, get cap values, order caps and recap these beauties. I think the tweeter distorting was a blessing in disguise, it's just the ticket I needed to start restoring these speakers. Who knows, maybe I'll start using them as my mains over my little IMF's for a while. I can only imagine how much better these are going to sound once the ferro fluid is replaced and the crossovers are redone. Oh and, I guess I have to replace those donuts on the B200's as well.
 
canuckaudiog said:
I'm gonna clean out the other tweeter tonight so, I'll snap some shots of it so you can see what it looks like. It's so easy to do though, so if anyone is following what I wrote you will see what I mean...
Click to expand...

Here's some info I have gleened from the SpeakerTalk board, but pictures speak a thousand words...

Taking apart a T33 is fairly straightforward. Use a Stanley knife to pry the diaphragm assembly away from the magnet top plate, complete with the glass fiber ring and wires. Try not to damage the thin yellow double sided adhesive tape (it is almost impossible).

Re-assembly and centering is easy with the semi-shear top plate locating pins but you will most likely have to source a substitute for the adhesive tape.

While it is apart, use blotting paper to remove any ferrofluid and residue from the gap. Then use folded over masking tape to remove anything else.

If you can get ferrofluid, refill.

Another post....

The tweeter dome is bonded to a ring that is stuck to the magnet with double stick tape. It is possible to gently lift it up using a thin bladed knife.

Once off, gently clean off the old ferrofluid from the coil using a soft cloth, then also remove the gunk from the magnet gap. This will be more difficult as it is of course attracted to the gap, but using Q-tips, masking tape wiped into the gap, and lots of patience, you may well be able to get the tweeter working again.

Of course it will no longer have the power handling it once had due to lack of ferrofluid, so be careful. It may be possible to find a source of new ferrofluid that you could put in.
 
SimplySound said:
Here's some info I have gleened from the SpeakerTalk board, but pictures speak a thousand words...

Taking apart a T33 is fairly straightforward. Use a Stanley knife to pry the diaphragm assembly away from the magnet top plate, complete with the glass fiber ring and wires. Try not to damage the thin yellow double sided adhesive tape (it is almost impossible).

Re-assembly and centering is easy with the semi-shear top plate locating pins but you will most likely have to source a substitute for the adhesive tape.

While it is apart, use blotting paper to remove any ferrofluid and residue from the gap. Then use folded over masking tape to remove anything else.

If you can get ferrofluid, refill.

Another post....

The tweeter dome is bonded to a ring that is stuck to the magnet with double stick tape. It is possible to gently lift it up using a thin bladed knife.

Once off, gently clean off the old ferrofluid from the coil using a soft cloth, then also remove the gunk from the magnet gap. This will be more difficult as it is of course attracted to the gap, but using Q-tips, masking tape wiped into the gap, and lots of patience, you may well be able to get the tweeter working again.

Of course it will no longer have the power handling it once had due to lack of ferrofluid, so be careful. It may be possible to find a source of new ferrofluid that you could put in.
Click to expand...

Those instructions strongly reflect what I have found. But it is true, pictures are indeed worth a thousand words. I've got another project to work on first tonight (some AR3a's) but after that is complete I am going to tackle this.

You have to give a lot of credit to Kef, they made servicing these speakers a real breeze. I mean you pop the enclosure off and there is a PCB with crimp connectors, and it just comes right off! Super super easy. I didn't have to desolder a single thing and I was able to fix the tweeter, it's seriously the most painless repair I've ever done. So I am looking forward to getting this restoration underway, let's hope the rest of the speaker is just as serviceable.
 
Last edited:
Little update guys.

Well, as it would turn out, the tweeter distorting was not the ferro-fluid in the tweeters. It was the receiver itself. Who woulda thunk that. I noticed it because all of a sudden it started distorting again, after taking out the fluid. So I thought, it's either a bad tweeter or the receiver is no good. And it turned out to be the receiver. Regardless, it got me started on the restoration of these speakers and also improved the HF response considerably. I'm kinda glad it happened, although now I have a receiver to sort out.

Anyhow, I've done some researching into recapping the crossovers. I understand what makes these so complicated, that the parts were computer-matched to the specific drivers in the cabinet. The problem is by this point, nearly 30 years later, the capacitors have degraded. At least, that's been my experience with speakers this old. At this point in time it's impossible to actually match the original parts with modern replacements, you'd need Kef's computer system to do that. Instead, what can be done, is you take the crossover out, and e-mail the list of values to Falcon Acoustics, and they will supply a matched 2% toleranced set of Alcaps to replace the ones on the boards. You just can't expect to get the factory values, unless Kef has them recorded somewhere.

I'm having difficulty getting at the crossover, otherwise I'd have the parts ordered, so if anyone has any tips on removing the woofers in the 104/2's please help me out, I can't seem to get the bottom one out which I understand you have to do first to get the pole and the top woofer out.

So for now, the restoration is on hold until I can get at the crossovers and get the woofers out. They are due for a recap, replacing the donuts and refilling the ferro fluid. I've got just about all my bases covered, so it's only a matter of time more or less.
 
canuckaudiog said:
I've got just about all my bases covered, so it's only a matter of time more or less.
Click to expand...

Oh don't we all know that! ;)

Thanks for the update Jeff, I'm still trying to get my second IMF finished, before I start jumping into a "pile" of KEF R107's I have lying around!

Aren't old speakers fun! :thmbsp:
 
canuckaudiog said:
Little update guys.

Well, as it would turn out, the tweeter distorting was not the ferro-fluid in the tweeters. It was the receiver itself. Who woulda thunk that. I noticed it because all of a sudden it started distorting again, after taking out the fluid. So I thought, it's either a bad tweeter or the receiver is no good. And it turned out to be the receiver. Regardless, it got me started on the restoration of these speakers and also improved the HF response considerably. I'm kinda glad it happened, although now I have a receiver to sort out.

Anyhow, I've done some researching into recapping the crossovers. I understand what makes these so complicated, that the parts were computer-matched to the specific drivers in the cabinet. The problem is by this point, nearly 30 years later, the capacitors have degraded. At least, that's been my experience with speakers this old. At this point in time it's impossible to actually match the original parts with modern replacements, you'd need Kef's computer system to do that. Instead, what can be done, is you take the crossover out, and e-mail the list of values to Falcon Acoustics, and they will supply a matched 2% toleranced set of Alcaps to replace the ones on the boards. You just can't expect to get the factory values, unless Kef has them recorded somewhere.

I'm having difficulty getting at the crossover, otherwise I'd have the parts ordered, so if anyone has any tips on removing the woofers in the 104/2's please help me out, I can't seem to get the bottom one out which I understand you have to do first to get the pole and the top woofer out.

So for now, the restoration is on hold until I can get at the crossovers and get the woofers out. They are due for a recap, replacing the donuts and refilling the ferro fluid. I've got just about all my bases covered, so it's only a matter of time more or less.
Click to expand...

There is a good video on youtube on how to take apart the speakers and replace the annulus or whatever the donut ring thingy is called...I cannot link to it because I am at work and they block it. Just search Youtube. I think getting the cabinet apart and removing the metal bar that runs down the center of the cabinet is the hardest part. I need to do the same thing.

I am not going to change my caps I do not think it is necessary yet. I really do not listen to mine every day like I should lol. I have them set connected to a Marantz 1060b along with some Pioneer CS-99as which I just found. Of course the KEFs are better but I like the Pioneers too. Just better not run both sets at once....
 
Just to let you know that the HF drivers for the KEF 104.2 are non-existent.... Mine died and KEF said the original drivers are no longer available.
 
Jon S said:
Just to let you know that the HF drivers for the KEF 104.2 are non-existent.... Mine died and KEF said the original drivers are no longer available.
Click to expand...


The Morel MDT29 is an (almost) drop-in replacement. There's a great YouTube video on replacing the tweeter and getting the Morel magnet assembly to fit.
 
good_news_everyone-525x296.png


Good news everyone!

I now have the official disassembly instructions from Kef in PDF format for the Kef 104/2, and I also have them for the 105/3.

If you would like a copy, please PM me your e-mail address and I will forward it along to you.

Now that I have these, it's time to get back into pulling those Kef's apart!
 
All right guys, a little progress. I have ordered the donut foam rings for the inner woofers. They have been shipped and are en route.

Also, I decided to fix up the grills. They had been attacked by a cat and also the top two pegs broke off on both of them, so I reglued those back on with super glue and then I took a lighter and reduced the snags. They actually turned out pretty nice, and I think the speakers look really smart with them on:

photo2hh.jpg


Now I just need to get onto getting at those crossovers.
 
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