KEF 104/2 restoration and crossover recap

[leesonic]

I started taking apart some KEF 104/2s that I'm working on for a friend and fellow AKer. I followed the directions in this excellent thread, and everything went smoothly. Here is the first one I took apart. Lay down some cardboard, and raise one end with a piece of wood to protect the rear terminals.



Remove the four allen bolts, and the mid/tweeter unit comes right off. There is even a little diagram to show where the connections go. I made sure to mark which ones go to the upper mid and which ones to the lower, but I will verify these when I get them back together.




Behind the mid/tweeter unit is an access panel.



Removing this reveals... a woofer with a rotten doughnut ring.



Removing the bottom access panel...



...a woofer with wire nuts on. Doesn't look factory to me.



In order to remove the woofers, it helps to have a long extension bar like this one. It stops the ratchet from sticking to the woofer magnet. If the nut on the woofer turns the screw, use one of these right angled screwdrivers to hold it. It's easier than a "conventional" screwdriver, and reduces the risk of slipping and putting a hole in the cone.



The second one went pretty much like the first, but the mid/tweeter unit was on upside down. These woofers had wire nuts on them as well.

Both crossovers are out. Lots of KEF and Alcap branded caps here. Some are labelled LL, which according to Falcon Acoustics stand for "low loss".



Four woofers. One rotted foam doughnut, one that looks a little bit off-center, the other two seem to be OK. Glad they have rubber surrounds though.

 

[nj pheonix]

 

[baco99]

looks like someone had already gone in and replaced the bottom woofer donuts a few years ago and instead of de-soldering and re-soldering the wires, they just snipped them and wire capped them.

 

[leesonic]

All the old doughnuts cleaned off. The sockets in between all the drivers were used to hold the center of the doughnut while it glued.



The doughnut sits slightly off the cone, so I used some pencils and elastic bands to hold the cones up while they were gluing. I love the shape of these woofer baskets, but it means the elastic bands kept slipping off, hence the tape holding them in place.

 

[leesonic]

New caps for old, new caps for old...

Recapped the crossovers today. I managed to get a set of matched caps from Falcon Acoustics over in the UK. What they apparently do is test a bunch of caps with 10% tolerance, and sort them into groups of 5% or 2% tolerance. Keen eyed viewers might notice the small piece of sandpaper. I like to sand down the legs of new components just to give a nice clean surface for the flux to work its magic on. Am I the only one who does this?



All done, except for the two missing 4.2uF caps, I will have to contact Falcon about that. They didn't have any 240uF caps, so I used two 120uF in parallel.

Wow! I haven't seen that many blue cans since my last session drinking Blue Moon... :beer:

 

[canuckaudiog]

Nice work! Brings back memories

 

[writethis]

Beautiful work Lee - I'm always impressed. I have a spare set of KEF crossovers, and a precision matched recap kit from Falcon in the post. Might have to see if you'll do the honors once I'm ready to move forward.

 

[baco99]

well worth the effort!

 

[leesonic]

Replacing the ferrofluid in the tweeters.

Today, I set about replacing the ferrofluid in the tweeters, I bought the ferrofluid from Parts Express. Here they are, a pair of KEF T33 tweeters, looking like two big eyes...



Diaphragm comes off with careful use of a sharp knife. I used a chisel shaped blade in an Xacto knife, I think the blade is #18.



Cleaning out the old ferrofluid. I used some pieces of card I had lying around, I think they came from Staples or somewhere. I used it dry at first, but as I got more out, I dipped it in rubbing alcohol. I also folded it over to make it thicker.



After a while, all should be clean down in the magnet gap.



Here is the new ferrofluid added. I couldn't take a picture of me adding it, since I needed more hands/arms than I have, one to hold the camera, one to hold the flashlight, and one to hold the ferrofluid. The ferrofluid sits in the magnet gap, it doesn't actually go down into the back of the magnet and pole piece assembly.



Cleaning the ferrofluid off the voice coil before re-installation.



After I got everything back together, I tried the tweeters out using nothing more technical than connecting them across the speaker leads with a 3.3uF capacitor. Everything sounded good to me...

Lee.

 

[leesonic]

Cabinet work...

I tried tidying up the cabinets on these. One thing that's always a problem is fixing what someone else has done. These cabinets have clearly been worked on before, there were a whole bunch of scratches from an orbital sander, as well as some dings that needed to be sanded out (circled in yellow). They also looked like they had polyurethane or something put on them.




Trying to figure out what happened here. If the cabinets had been stained, surely the stain would penetrate the wood all the way through? Yet sanding them down revealed these light patches, I got rid of them by applying more stain.





Disaster! Sanding down the longest side, I managed to break of a piece of veneer. This corner had swollen, and whoever fixed them before used just plain wood filler instead of using glue.



I stabilized this by injecting wood glue with a syringe, the particleboard underneath was very flaky. It was a laborious process, I had to add the wood glue, then put a piece of veneer on, then add more glue. I should be able to hide the joins with a stain pen to match the color of the stain I used.



This is what is nice about a proper oiled wood finish, as opposed to a fake poly or varnish effect IMHO. The wood itself is shiny, as you can see by the reflection of the logo from the box the cabinet is standing on.

 

[leesonic]

Putting them back together...

Putting them back together again. Tools you need are :

Crossover board - 8mm deep socket.
Woofer bolts - 7mm deep socket.
Brace bar - 10mm deep socket.
Midrange enclosure - probably metric, but a 5/32" allen works just as well.
Access panels - Posidriv bit number 2. *

* Do yourself a favor, don't use a normal Philips bit, get yourself a proper Posidriv bit. It grips these screws even if they've been a bit rounded off. I was able to use all but two of the original screws, the last two I cut a slot in the top with a Dremel and used a flathead screwdriver.

Crossover gets maneuvered in via the top woofer hole. It is easier to plug the multi-way connector in before you get it all the way in.



Top woofer fitted. Check the gasket on the back of the woofer, if it is compressed, replace it.



Brace bar refitted to the top woofer, feed this in through the bottom hole, and use a small flashlight to help align it with the bolt that goes through the center of the woofer magnet.



Put the upper woofer enclosure stuffing in, making sure that it doesn't sit on the cone.



Bottom woofer goes in. It's easier to take the foam out rather than squeeze the woofer in past it.



Put the foam back in, followed by the stuffing. These woofer enclosures need to be sealed, so make sure the seals are good, I used the speaker sealing tape from Parts Express.



Make sure you connect these wires up inside, otherwise you'll have no sound. Remember, the black and white wires from the terminal, the white wire is the positive, the black wire is the negative.



The upper enclosure access panel needs sealing tape on it as well. From the factory, it was stuck on the cabinet side. I chose to stick it on the actually panel, since this is smoother.



Get out your hot melt glue gun (what do you mean, you don't have one?), and glue the port trim pieces in. After this is done, resist the temptation to move or lift the cabinet using these, otherwise they'll pop right out again.



Midrange/tweeter enclosure wiring is labelled, just take your time and get each wire back where it belongs. I tightened up the spade connectors by squashing them slightly with some pliers.



Here they are next to my Genesis 320s.

 

[mech986]

Great work and even better photo documentation!

 

[baco99]

Two thumbs up!!

 

[Franz Kafka]

Wow! Lee, thank you so much! I have a pair of 104.2s that I'm planning to start on soon. Your photodocumentation is brilliant and will make my life much easier.
This is really fantastic! You make thr work seem much easier than I'm sure it will be, especially for someone like me with little experience. I can't wait to get started.

I actually have two pair of 104.2s and plan to combine the best of the two into one pair. The project is meant to be a learning experience for me so I'll take my time and enjoy it.

Thanks again and bravo!

 

[Franz Kafka]

And I should have added my thanks for your link to the previous thread from last year, that too is tremendous work. You guys are as smart as you are generous with time. What a great site!

 

[canuckaudiog]

Wow! Lee, thank you so much! I have a pair of 104.2s that I'm planning to start on soon. Your photodocumentation is brilliant and will make my life much easier.
This is really fantastic! You make thr work seem much easier than I'm sure it will be, especially for someone like me with little experience. I can't wait to get started.

I actually have two pair of 104.2s and plan to combine the best of the two into one pair. The project is meant to be a learning experience for me so I'll take my time and enjoy it.

Thanks again and bravo!

Franz, the work is actually as easy as it looks Kef designed the speakers to come apart, so these are fairly simple to restore. It's a bit time consuming because of the number of steps, but the work itself is not challenging in the least.

Good luck with your project!

 

[Raynald]

Wow, great document of your superb work. I am sure that will help a lot of members. The tweeters section will probably come in handy for my 107s some day.

Thanks.

 

[goonybird]

Reading this and similar posts has finally given me the courage to do my 104/2s
I have had mine since the mid 90's (looks like they are made 1988)
Already done the ferrofluid on the tweeters which improved them. They don't sound as dull.
Just finished the central doughnuts and used Moyen RS-3087 (JBL) adhesive.
Expensive but dries black like the original adhesive.
Was going to replace the Caps but some are becoming unavailable at Falcon Acoustics (who also ingnored my emails!)
So checked caps, coils, resistors for any obvious open circuit and resistance checks and all similar, in cross comparison (and a spare full crossover for comparison) so had to leave alone.
Did re-cable tie a few coils as now a bit loose, and affix capacitors so they didn't rattle.
When refitting the mid/hf unit I rotated the tweeter through 180 in case the ferrofluid sinks to the bottom (just a mad thought!)
Put a bit of extra foam between the wood crossbrace and the tension bar.
Replaced rubber grommets on speaker mounting holes.

Does anyone know what the screw does on the back of the mid units?

 

[audiodon]

Within the last three months, I have had two positive business transactions with Falcon Acoustics.

Rather than email falcon acoustics with questions, if you just order the capacitor upgrade, you'll be in good shape and it will come. See my review here:
http://www.audiokarma.org/forums/showthread.php?t=633986

Don't order the crossover kit. Order the cap upgrade.

 

[nj pheonix]

Finally had the opportunity to visit Lee Monday night. Had a pleasant but brief listening and BS session with him and took these home. Too late to play when I got home. Came home from work Tues. and dryer crapped out (another distraction) Listened to them for about 5 minutes in what was set up which in itself was an experiment so no idea how they really sound. Finally today listening now. my recently acquired prized Fisher seems to really like these. (I also now think my Polks which I thought were better than most opinions seemed to be, may be more wanting than I thought or maybe its a synergy thing) In any event , anybody thinking of these I think will be really happy and anyone who doesn't want to do the restore themselves will be really happy with Lee. Thanks again Lee!