KEF 103/3 Tweeter

[ktm-don]

I'm repairing a set of KEF 103/3 speakers that have a lot of sentimental value to me. As expected, the ferro fluid in the tweeters had turned into a gummy mess. I should have followed advice of others and cut the wires when removing the tweeters, but I pushed back the rubber sleeving and unsoldered the connections. In the process, I rotated the terminal on one tweeter, and broke the voice coil wire.

I've researched here and on DYI audio, the go-to replacement for the T33 SP1210 tweeter seems to be the Morel MDT29-4. I can't find stock, Madisound has been out of stock for some time. They expect to eventually have parts again, but I'd like to have a back-up plan. Since the tweeter is 4 ohms, the options are more limited. The OEM units are specified as 93 db sensitivity.

I have a cheap pair of diaphragms on order from China through the auction site. The rings around the dome are small, and not convinced that these are quality replacements. Used T33 units can be had for $100, but I expect the fluid to be dried out in any OEM part by now.

The T33 has a 95 mm square adapter plate, the tweeter itself is about 72 mm in dia. The Dayton RST28F-4 looks like a nice dome tweeter, but the OD of the outer ring is 104 mm. That would require a lot of work to adapt, and I'm not eager to modify the cabinets. Speaker Exchange had nothing to offer, Midwest Speaker Repair has a 1" dome, but the mechanical mounting would be challenging. There are no suggested replacements from KEF, not surprising for a speaker made in the mid 80's!

Is anyone aware of alternative solutions that I've not found?

Thanks in advance!

 

[Buck Rogers]

Easy one, Time to upgrade.

Vifa "Ring Radiator" they come in lots of sizes.

Play nice with crossovers, Super flat response.

Superb sounding, High power handling. Great price...

 

[ktm-don]

Thanks for the lead! I'm following up on that. If I understand the situation, Vifa brand is now Peerless by Tymphany. I see them on Parts Express and other sites. I see the model in your picture has two sensitivity ratings, there were no conditions listed on the KEF part, just 'sensitivity 93 db'.

Half Space Sensitivity @2.83V db@2.83V/1M dB 90.84
Half Space Sensitivity @1W/1M db@1W/1M dB 87.2

Aside from that, the OD of the XT25 is also 104mm, I'll look for physically smaller ring radiators, or contemplate what it would take to fit the larger OD.

Thanks again for opening up some options other than the conventional 1" dome.

 

[DOBIEGUY]

Sorry for your unfortunate situation. I‘ve mentioned cutting the wires in numerous threads.
If your other tweeter is OK you should wait for the correct T-33 to come along. They show up on Ebay, but not often.
Also look for a single REF 102, the do show up.
Replacing the originals with something else just because they drop right in is not a good option. Hacking up the cabinet to put a that round tweeter in the square opening is a non-starter.
Your KEFs deserve better.
Good luck

BTW—— got the KUBE and the correct stands?

 

[ktm-don]

From the photo, it looks like the outer ring 'might' be removable on the XT25. Perhaps I could swap the voice coil and magnet to the KEF adapter plate?

 

[ktm-don]

Sorry for your unfortunate situation. I‘ve mentioned cutting the wires in numerous threads.
If your other tweeter is OK you should wait for the correct T-33 to come along. They show up on Ebay, but not often.
Also look for a single REF 102, the do show up.
Replacing the originals with something else just because they drop right in is not a good option. Hacking up the cabinet to put a that round tweeter in the square opening is a non-starter.
Your KEFs deserve better.
Good luck

BTW—— got the KUBE and the correct stands?

Yep, I have the Kube and its power supply. The original stands were damaged in a Texas flood, I remade them last winter.
I have the desire to keep 'em original, but if I can find a suitable new replacements I would consider it. I'm not excited about buying old, used tweeters on line.

 

[ktm-don]

Due to no availability of the Morel 4 ohm tweeters, I just finished installing a set of Audax TWO25A2 tweeters in my 103/3 speakers. The Audax specifications were very close to the original T33. The original round tweeter face plates removed easily, I fabricated a pair of 95mm square plates to fit the KEF cutout. The KEF cabinet has an interesting oval cut out for the tweeter magnet, so the terminals of the Audax tweeters had clearance without any cabinet mods.

I replaced the disintegrated woofer dust caps, certainly an interesting arrangement with the support rod bolted to the magnet of the woofer. Curious what the thought was behind that design choice - rigid mounting of the woofer? I did need to rotate the woofer to get the best alignment with the rod and the mounting hole in the speaker base.

So, last night I was able to fire up the venerable KEF's, they have been languishing in the basement for the past couple of years. I rebuilt the bases last winter, and finally decided to wrap up the project before year-end. I put on the Tracy Chapman album that first sold me on the speakers 30 years ago - can it really be so long? The KEF's sounded great, look great, and brought me back full circle on a pair of speakers that I bought here in Ann Arbor and shipped to my sister so many years ago. They compare nicely to the B&W CDM 7 that they displaced, although I'm still getting things dialed in. I guess I like something about British speakers. I'm driving them with a Denon PMA-900, which is one of my favorites.

Merry Christmas AK folks, let the tunes roll in 2024!

 

[Pete B]

Old thread: https://audiokarma.org/forums/index.php?threads/help-me-pick-a-replacement-tweeter-kef-107.175162/

Different system, same tweeter.

 

[ivandezande]

Nice. Midwest Speaker has a drop-in but you'd need to mess with the mounting.

I had a pair but no Kube, and they were still pretty good.

 

[Dony]

Due to no availability of the Morel 4 ohm tweeters, I just finished installing a set of Audax TWO25A2 tweeters in my 103/3 speakers. The Audax specifications were very close to the original T33. The original round tweeter face plates removed easily, I fabricated a pair of 95mm square plates to fit the KEF cutout. The KEF cabinet has an interesting oval cut out for the tweeter magnet, so the terminals of the Audax tweeters had clearance without any cabinet mods.

I replaced the disintegrated woofer dust caps, certainly an interesting arrangement with the support rod bolted to the magnet of the woofer. Curious what the thought was behind that design choice - rigid mounting of the woofer? I did need to rotate the woofer to get the best alignment with the rod and the mounting hole in the speaker base.

So, last night I was able to fire up the venerable KEF's, they have been languishing in the basement for the past couple of years. I rebuilt the bases last winter, and finally decided to wrap up the project before year-end. I put on the Tracy Chapman album that first sold me on the speakers 30 years ago - can it really be so long? The KEF's sounded great, look great, and brought me back full circle on a pair of speakers that I bought here in Ann Arbor and shipped to my sister so many years ago. They compare nicely to the B&W CDM 7 that they displaced, although I'm still getting things dialed in. I guess I like something about British speakers. I'm driving them with a Denon PMA-900, which is one of my favorites.

Merry Christmas AK folks, let the tunes roll in 2024!

Hello ktm-don,

Good work installing the Audax TWO25A2 tweeters into your 103/3. I recently purchased a pair of Kef 102 to keep the T-33 tweeters as backup for my Kef 107. Unfortunately when replacing the ferrofluid in the T33 I damaged the voice coil/diaphram in one of them. So now I am looking to replace the T33 in my 102 with Audax TWO25A2 tweeters. Do you have any info on the 95mm square plates that you fabricated to fit the KEF cutout? What material did you use? Are they completely flat or are they coned like the original? Your help would be greatly appreciated!

Thanks

Don

 

[ktm-don]

Hi Don:

The faceplate of the Audax tweeters is flat, the plate I fabricated was made from some aluminum scrap that I had on hand. Once the plate is fabricated, the switchover is easy. I've attached a simple 2D print that I drew for spotting the holes. The corner radius shown on the print is a guess, I used a stationary belt sander to round the corners to match the original adapters.

The only other recommendation is to use quick connect / Faston connectors to attach the wiring to the Audax. The terminals are staked to a plastic ring, which can soften when heat is applied if you solder the connections.

There are replacement domes advertised for the T33 for sale on the auction site from China, for $12 or so. I bought a pair, and will eventually try resurrecting the original T33 tweeters. There are probably other tweeters out there that could have the faceplates removed and replaced, but the specs on the Audax parts looked very close to the T33 SP1210, and I had seen in another post that the faceplates were flat and easy to swap.

Good luck, if I can answer any other questions just let me know.

 

[Dony]

Hi Don:

The faceplate of the Audax tweeters is flat, the plate I fabricated was made from some aluminum scrap that I had on hand. Once the plate is fabricated, the switchover is easy. I've attached a simple 2D print that I drew for spotting the holes. The corner radius shown on the print is a guess, I used a stationary belt sander to round the corners to match the original adapters.

The only other recommendation is to use quick connect / Faston connectors to attach the wiring to the Audax. The terminals are staked to a plastic ring, which can soften when heat is applied if you solder the connections.

There are replacement domes advertised for the T33 for sale on the auction site from China, for $12 or so. I bought a pair, and will eventually try resurrecting the original T33 tweeters. There are probably other tweeters out there that could have the faceplates removed and replaced, but the specs on the Audax parts looked very close to the T33 SP1210, and I had seen in another post that the faceplates were flat and easy to swap.

Good luck, if I can answer any other questions just let me know.

Hello ktm-don,

Thanks for providing the 2D drawing of the faceplate that you fabricated. Your information will be very helpful. One question that I have is what is the thickness of your plate? I don’t believe I saw that dimension on the drawing.

When searching around I did find information about the Dayton RST28F in which the person removed the Dayton faceplate and then enlarged the dome opening on the KEF faceplate from 1” to 1-1/8” to allow the tweeter to fit into the KEF faceplate. They advised that everything else matched including the faceplate to magnet screw holes. So it appears that the Dayton might make an easier replacement that might look more original. The only downside would be the permanent modification of the Kef faceplate.

With that conclusion, I will probably try to fabricate a new faceplate out of aluminum or have them made on a 3D printer thus allowing me to keep the KEF faceplates in tact so that I can also try to replace the faulty dome in my damaged T-33. If not, I will keep an eye open on the auction site for a T33 - SP1210 that I can purchase and have the ferrofluid replaced to have a standby replacement If needed.

If you could please keep this thread advised on the success of your dome replacement for the T33 that would be helpful. I am somewhat suspect that the $12 domes from china will be acceptable replacements. I will keep my eyes open for better quality dome replacements prior to going down that path.

Thanks

Don

 

[ktm-don]

Hello ktm-don,

Thanks for providing the 2D drawing of the faceplate that you fabricated. Your information will be very helpful. One question that I have is what is the thickness of your plate? I don’t believe I saw that dimension on the drawing.

When searching around I did find information about the Dayton RST28F in which the person removed the Dayton faceplate and then enlarged the dome opening on the KEF faceplate from 1” to 1-1/8” to allow the tweeter to fit into the KEF faceplate. They advised that everything else matched including the faceplate to magnet screw holes. So it appears that the Dayton might make an easier replacement that might look more original. The only downside would be the permanent modification of the Kef faceplate.

With that conclusion, I will probably try to fabricate a new faceplate out of aluminum or have them made on a 3D printer thus allowing me to keep the KEF faceplates in tact so that I can also try to replace the faulty dome in my damaged T-33. If not, I will keep an eye open on the auction site for a T33 - SP1210 that I can purchase and have the ferrofluid replaced to have a standby replacement If needed.

If you could please keep this thread advised on the success of your dome replacement for the T33 that would be helpful. I am somewhat suspect that the $12 domes from china will be acceptable replacements. I will keep my eyes open for better quality dome replacements prior to going down that path.

Thanks

Don

Hi Don - I don't remember the plate thickness, guessing it was around 0.10" or so. I did take a look at the Dayton tweeter, one thing I noticed was the free air response was much different than the the T33. Since this value is well below the crossover value, I'm not sure it's significant. I did not want to modify the original KEF plates. There are a few T33 models on the auction site, but the cost was generally $100 each. That and the fact that they will need service upon arrival did not make them very interesting to me.

When I get around to the dome replacement I'll let you know how that works out. Since the 103/3 speakers are up and running, it's a low priority project for me. The only parts that I could find were lo-cost sourced from China, or you could buy a similar part from a German site, but it sure looked like the same dome. There is very little skirt around the dome to glue it to the magnet assembly, so no way to use the original alignment pins. I have seen posts from folks that have done it by applying a volt or so to the domes to center them.

Let me know if you where you end up with your project, and best wishes for 2023!

 

[Dony]

Hi Don - I don't remember the plate thickness, guessing it was around 0.10" or so. I did take a look at the Dayton tweeter, one thing I noticed was the free air response was much different than the the T33. Since this value is well below the crossover value, I'm not sure it's significant. I did not want to modify the original KEF plates. There are a few T33 models on the auction site, but the cost was generally $100 each. That and the fact that they will need service upon arrival did not make them very interesting to me.

When I get around to the dome replacement I'll let you know how that works out. Since the 103/3 speakers are up and running, it's a low priority project for me. The only parts that I could find were lo-cost sourced from China, or you could buy a similar part from a German site, but it sure looked like the same dome. There is very little skirt around the dome to glue it to the magnet assembly, so no way to use the original alignment pins. I have seen posts from folks that have done it by applying a volt or so to the domes to center them.

Let me know if you where you end up with your project, and best wishes for 2023!

Hi ktm-don,

Thanks for your prompt reply. I confirmed that the existing KEF faceplate is around 0.10 inches (2.5mm). If I go with aluminum then I will stick with that thickness, if I get the plate made in 3D printer in plastic then I will probably increase the thickness to be around 5mm to ensure the plastic will be resistant to cracking when I attach the tweeter mounting screws.

I will probably still keep an eye open for a used T33 on the auction site even if it still needs fresh ferrofluid. I think having good T33 tweeters in my KEF 107 is still worth $100 to $200, especially if it lasts another 35 years.

I will continue looking for a good source for a new dome/diaphram to repair my damaged T33. l hope someone will make new domes that work with the alignment pins, if so I will be a customer that will buy at least 4 domes as spares.

I will keep you posted on my project. All the best to you and your family for 2024!

Regards

Don

 

[Dony]

Just to keep this thread alive, I have now had the faceplates made up in a 3D printer and installed a Audax TWO25A2 to replace the T33 - sp1210 in my KEF 102.

So far the sound quality is very close. I would go as far to say if I had to replace the T33 in my KEF 107, that the Audax tweeters would be acceptable. I think the only revision I might make is to have the faceplates made in aluminum using a CNC machine.

And now when I replace the T-33 in my second KEF 102 then I will have at least one functional spare T33 for my KEF 107.

 

[ktm-don]

Glad that all worked out for you Don. I can't really compare the original sound of the 103/3 tweeters to the rebuild using the Audax drivers, since I had not heard the speakers in 30 years. I've not been doing much critical listening, but I'm very satisfied with the Audax units.

 

[Dony]

Glad that all worked out for you Don. I can't really compare the original sound of the 103/3 tweeters to the rebuild using the Audax drivers, since I had not heard the speakers in 30 years. I've not been doing much critical listening, but I'm very satisfied with the Audax units.

Hi ktm-don,

Well so far the Audax tweeter is a comparable to the Kef T33 - SP1210 with new ferrofluid In my KEF 102.

Currently the Audax has only been installed for about 24 hours so I expect the SQ to get better given more play time. I would like to maybe compare the Audax with the Morel MDT-29-4 ohm at some point but right now there is no stock available on the Morels so I will continue with the Audax.

Ultimately it is good to know there are viable replacements for the Kef T33 if mine ever stop working in my KEF 107.

 

[ktm-don]

Thanks, if you do eventually try the Morels or other tweeters, please update the thread. I'm still curious.
Happy listening!

 

[ktm-don]

What a coincidence - I just received this email from Madisound:
"The Morel MDT29-4 (4 ohm) Textile dome tweeters are now back in stock and ready to ship!"

 

[Dony]

What a coincidence - I just received this email from Madisound:
"The Morel MDT29-4 (4 ohm) Textile dome tweeters are now back in stock and ready to ship!"

Hi ktm-don,

Good to know that the Morel MDT29-4 (4 ohm) are available once again from Madisound.

I have some other projects that are going to take priority as the Audax tweeters are now installed into my KEF 102 and functional.

At some point in time in the future I will consider ordering a pair of the Morels from Madisound just to give them a try as a comparison to the Audax for replacing the KEF T33.