KEF 107 T33 replacement?

[Thundermud]

I have read a few forums that recommend using the Morel MDT29 tweeter as a replacement for the KEF 107. I have also recently seen a listing on Fleabay that claims to fix the original tweeter by replacing the Ferrofluid.

Here is a link to the Fleabay replacement:

http://www.ebay.com/itm/KEF-TWEETER-REPLACEMENTS-FOR-104-2-T33-SP1191-107-105-103-102-MORE-/251195268088?pt=Vintage_Electronics_R2&hash=item3a7c679bf8

Here is the link for the Ferrofluid replacement service:

http://www.ebay.com/itm/Repair-rebuild-of-dried-ferrofluid-KEF-T-33-tweeter-50-each-107-104-102-etc-/130736561488?pt=Vintage_Electronics_R2&hash=item1e70819d50

Any suggestions would be greatly appreciated.
Thanks!

 

[SimplySound]

I have read a few forums that recommend using the Morel MDT29 tweeter as a replacement for the KEF 107...

Any suggestions would be greatly appreciated.
Thanks!

Well this will get interesting. I'm embarking on some of this stuff. :yes:

I too have read what you say about the Morel. I would say that it might be interesting to try to see how it sounds. Don't get rid of the original T33's though. Having the original driver is important to maintain the value of the speakers. You might also want to tweak the X-over to get the sound you want, but I don't even know where to begin there!

As for ferrofluid; I am going to attempt to replace mine. I hear it isn't really that hard but requires some patience and focus. The key is having the right Ferro-fluid. I'll post some info on that as I progress.

Good luck with whatever you decide to do.

 

[canuckaudiog]

Well this will get interesting. I'm embarking on some of this stuff. :yes:

I too have read what you say about the Morel. I would say that it might be interesting to try to see how it sounds. Don't get rid of the original T33's though. Having the original driver is important to maintain the value of the speakers. You might also want to tweak the X-over to get the sound you want, but I don't even know where to begin there!

As for ferrofluid; I am going to attempt to replace mine. I hear it isn't really that hard but requires some patience and focus. The key is having the right Ferro-fluid. I'll post some info on that as I progress.

Good luck with whatever you decide to do.

I've been strongly considering replacing the ferro-fluid in my Kef 104/2 T33's as well. Doug, if you get around to it, please post your findings. That ferro-fluid has been tricky for me to track down.

 

[kymers]

I have a pair of C-80's with T33's, so I'd like follow along as well!

 

[mech986]

Caution, I am not sure all T33's have ferro fluid installed in them. Best to double check the manufacturer's literature and see if their specs or description include ferrofluid in them. I do know the 104/2 and 107 do use ferrofluid.

Does anyone know if the ferrofluid dries or rusts, and would the rust be difficult to remove?

 

[SimplySound]

I've been strongly considering replacing the ferro-fluid in my Kef 104/2 T33's as well. Doug, if you get around to it, please post your findings. That ferro-fluid has been tricky for me to track down.

I believe the original fluid was APG 512A. This is discontinued and I believe a similar fluid is the APG S15n.

I'm still piecing this together, but that's as much as I have gotten so far. :scratch2:

 

[dave101260]

Any new info?

How has this endeavor panned out?

I have a pair of 107's and this is something I'm going to need to address sooner rather than later.

 

[orionkc]

I have a set of 105.4's. Does anyone know if the T-33's in these have the same problem as the others? Mine sound really good and don't appear to have lost any SPL. YET?

 

[baco99]

I and canuckaudiog have posted on this issue. Replacing the ferrofluid is easy and doable with strong results.

 

[canuckaudiog]

It turned out well. I picked up some ferro fluid and replaced it in several T33s, all of them making good improvements to the treble response. Highly recommended.


Sent from my iPhone using Tapatalk - now Free

 

[Dony]

Hello fellow KEF 107 fans,

Well, I will revive this old thread as it seems pertinent to what I am working on. Ultimately, I want to ensure I have backup T-33 SP1210 tweeters for my Kef 107.

What I have done is to purchase a pair of KEF 102 with a KUBE and the T-33 SP1210 tweeters. I proceeded to change the ferrofluid in the 102 tweeters but one of the diaphragms/voicecoils was damaged in the process. What I found out is the process is fairly simple but the diaphragms are very delicate.

So now I have one spare T-33 with the ferrofluid replaced and one that is damaged. I will not be replacing the ferrofluid in the T-33 in my 107 until absolutely necessary as there is a chance that it has already been done as I have confirmed the fact that the woofers have already been re-foamed.

So my question for other KEF 107 owners, did anyone ever use the The Midwest MT-1191, Vifa BC25TG15-04 or the Madisound version? And then there is the Audax TW025A2, which is also an option.

One of these options will replace the pair of T-33 in the KEF 102 so I can keep the originals. Seems like the Audax might be a good try for me as they are available in Canada and thus the shipping will be less with no additional duties or extra taxes.

There is some mention on the Falcon Acoustics website - "Audax TW025A2 is a high-quality 4 ohm 25 mm voice coil tweeter, a possible replacement for the KEF T33 but with no ferrofluid. SPICA T50 tweeter."

Any feedback and recommendations here would be greatly appreciated.

Thanks

Don

 

[SimplySound]

Well, I bought a Peerless by Tymphany BC25TG15-04 (new Vifa) from Madisound. It has the right specs and I thought I would get lucky and that the face-plate would unbolt and it might be a direct mount to the T33 SP1210 square face-plate. The bolt pattern is 58mm diameter which is a touch smaller than the T33 at 60mm, but I thought it might work.

Unfortunately, the coil/dome is molded to the Peerless BC25 face-plate, so if you unbolt it, you can't just drop the T33 square plate on. Some people talk about modify (hogging out) their heads to work, but I didn't want to do that so I sent it back without trying it.

I am thinking I might try the SB Acoustics SB26STCN-C000-4. It too looks like the right specs and it has a 4-bolt pattern of 63mm (pretty close). Thing is it has a wave guide built into it's face-plate. The diameter of the wave guide (magnet diameter) is 46mm, which is pretty much what the T33 has.

Problem is you will have to modify the T33 square face plate to remove the wave guide, but you don't have to go hogging out the heads!

I have some extra face-plates, so I'm thinking a 1-3/4" hole saw carefully removing the wave guide of the T33 face-plate will allow the SB to drop in and be bolted to it. Then the T33 plate can be bolted to the heads.

Only thing I see as a bit of an issue is that the SB will probably be 3-5mm proud of the faceplate which will change the phase alignment of the tweeter just a bit. Will it be noticible? Doubt it!

Other ideas?

 

[Dony]

Well, I bought a Peerless by Tymphany BC25TG15-04 (new Vifa) from Madisound. It has the right specs and I thought I would get lucky and that the face-plate would unbolt and it might be a direct mount to the T33 SP1210 square face-plate. The bolt pattern is 58mm diameter which is a touch smaller than the T33 at 60mm, but I thought it might work.

Unfortunately, the coil/dome is molded to the Peerless BC25 face-plate, so if you unbolt it, you can't just drop the T33 square plate on. Some people talk about modify (hogging out) their heads to work, but I didn't want to do that so I sent it back without trying it.

I am thinking I might try the SB Acoustics SB26STCN-C000-4. It too looks like the right specs and it has a 4-bolt pattern of 63mm (pretty close). Thing is it has a wave guide built into it's face-plate. The diameter of the wave guide (magnet diameter) is 46mm, which is pretty much what the T33 has.

Problem is you will have to modify the T33 square face plate to remove the wave guide, but you don't have to go hogging out the heads!

I have some extra face-plates, so I'm thinking a 1-3/4" hole saw carefully removing the wave guide of the T33 face-plate will allow the SB to drop in and be bolted to it. Then the T33 plate can be bolted to the heads.

Only thing I see as a bit of an issue is that the SB will probably be 3-5mm proud of the faceplate which will change the phase alignment of the tweeter just a bit. Will it be noticible? Doubt it!

Other ideas?

Hi Simplysound,

Well I have a single T-33 that I managed to save out of my 102 which I have replaced the ferrofluid. This will serve as a spare for my 107 and I will also keep my eye open for another spare on the auction site.

For the T-33 replacements in my 102 I am going with the Audax TW025A2 as there is currently stock available. The 4 ohm Morel is out of stock at the moment. I was also considering the Dayton RST28-4 as there has been 107 owners that have added them to the KEF faceplate by increasing the size of the dome opening to 1-1/8”. But after reviewing the options I decided to stick with the Audax and a custom flat faceplate to fit the tweeter and the Kef cabinet mounting which will allow me to keep the Kef tweeter mounting plates original in case I ever want to go back to the T-33.

I will continue to monitor this thread to see what the best replacement solution is going forward.

Thanks

Don

 

[SimplySound]

Hey Dony... So how did you mount the Audax? Do you have pics of your 'customized' face-plate?

 

[Dony]

Hey Dony... So how did you mount the Audax? Do you have pics of your 'customized' face-plate?

Hi SimplySound, the Audax tweeters are on their way in shipping.

I purchased a couple of 4" X 4" X 0.25" aluminum plates to prepare for the custom faceplates. I'm in the process of finding a machine shop that can make the necessary revisions to duplicate the exact KEF faceplate shape with the tweeter dome opening and screw mounting holes to specifically suit the Audax tweeter. I will use the factory Audax round faceplate as a template on the custom faceplate to ensure the dome opening and screw mounting holes are an exact match.

The only question now is it more economical to have the aluminum plates made up, or is it more cost effective to have the custom faceplates made in a 3D printer, so far I think the aluminum plate will be more cost effective but we will see.

 

[SimplySound]

I just ordered the SB Acoustic, so we can compare notes when you get yours pulled together Dony.

 

[Dony]

I just ordered the SB Acoustic, so we can compare notes when you get yours pulled together Dony.

Sounds good... Thx

 

[SimplySound]

OK, the SB Acoustic tweeter looks like it may work out pretty slick, but it will take some adapting. The bolt pattern lines up pretty close, and the diaphrams are identical. The height looks good and the fact it is a Neodymium magnet makes the installation easy.

The trick will be to lower the outer ring of the KEF face plate so that it brings the wave guide down into contact with the SB wave guide. I wish I had a milling machine to do this, but I might be able to get a pretty clean cut with a table saw. Will have to fixture it and take passes on each side. One issue I see though is that the back side of the actual wave guide on the KEF faceplate is flat, so I'll probably end up with a little gap when it engages the wave guide of the SB.

Before I do any of this, I think I'll just throw the SB into the R107 Head to get a quick sound check on it. It won't be ideal, but should give me some idea of the cross-over compatibility. The T33 is crossed at 2500Hz and this tweeter is spec-ed the same, so I'm thinking it shouldn't require any messing with the cross-over.

Bottom-line, if this works then all that gets modified is the face plates. And if you can get a couple of those as spares, you can always get the speakers back to original with no modifications (aka; drilling or hogging out) of the Heads. At least that's my rational for doing this.

Thoughts?

 

[SimplySound]

Also, at some point I do want to replace the Ferrofluid in my T33's. I'm really just playing around with the SB to see what it sounds like and whether it might be an improvement. It would give us another option over the Morel, Audax, Vifa, MW sources.

This is a good thread on the Ferrofluid options at SpeakerTalk (SpeakerGuru is/was an original KEF engineer). Here's a link to FerroTec and for posterity this is some aspects of the thread;

• KEF used to use the now obsolete APG512. From memory it was a 75cp fluid. i.e. the fluid was used primarily to increase conduction of heat to the metalwork, not to provide damping. The base fluid is a synthetic oil and I guess everything dries/evaporates eventually.
• In the APG L series, APG L17 would be the closest to the original low viscosity APG512.
  • APG311 looks closer still and has a higher temperature rating.
  • APG S15N looks to be close to the original in viscosity. If Ferrotec are cautiously recommending it, then it is probably the most suitable for T33 use.
• The exposed part of the T33 vc is high temperature cured epoxy, aluminium and CA (superglue) adhesive. Not much risk of a bad reaction with an oil based fluid, I think, but no guarantees.
• After some conversation with Ferrotec, it appears that due to the relative magnet strength the more critical parameter is the Gauss followed by viscosity. Therefore APGO77n is recommended as the best alternative with a gauss of 265/115cp.
  • Not sure what Ferrotec meant by that. There was never any explanation in their literature of what happens to the fluid if the field flux density is significantly greater or less than the quotes "Gauss"
  • When KEF tweeters first acquired ferrofluid, the primary aim was to reduce the thermal resistance of the air gap whilst introducing as little mechanical damping as possible. A viscosity of ~75cp does this.
• The magnet gap should "only just" be filled with ff. If 100ul (0.1ml) does not completely go right around the gap is does not matter. Do not overfill the gap. The vc length is less than the gap but takes up at least a third of the gap volume, so, if the gap is "only just" full, there will be sufficient coverage as the vc is inserted and displaces the ff.

Feel free to add any insight into this summary with your experiences.

 

[Dony]

OK, the SB Acoustic tweeter looks like it may work out pretty slick, but it will take some adapting. The bolt pattern lines up pretty close, and the diaphrams are identical. The height looks good and the fact it is a Neodymium magnet makes the installation easy.

The trick will be to lower the outter ring of the KEF face plate so that it brings the wave guide down into contact with the SB wave guide. I wish I had a milling machine to do this, but I might be able to get a pretty clean cut with a table saw. Will have to fixture it and take passes on each side. One issue I see though is that the back side of the actual wave guide on the KEF faceplate is flat, so I'll probably end up with a little gap when it engages the wave guide of the SB.

Before I do any of this, I think I'll just throw the SB into the R107 Head to get a quick sound check on it. It won't be ideal, but should give me some idea of the cross-over compatibility. The T33 is crossed at 2500Hz and this tweeter is spec-ed the same, so I'm thinking it shouldn't require any messing with the cross-over.

Bottom-line, if this works then all that gets modified is the face plates. And if you can get a couple of those as spares, you can always get the speakers back to original with no modifications (aka; drilling or hogging out) of the Heads. At least that's my rational for doing this.

Thoughts?

Hello SimplySound,

So it appears that the SB Acoustic tweeter may be a good replacement option for the KEF T-33. If you can please keep the thread updated on the overall SQ and installation difficulties that would be great. Currently I am awaiting the correct Audax tweeters because even though I specifically requested the 4 ohm units they sent the 8 ohm versions by mistake.

For the faceplate revisions required, I've sourced a local 3D printing company and they have quoted about $25 to make up new face plates in hard plastic to suit the Kef cabinet mounting and the Audax tweeter mounting holes. This will save me from modifying my original Kef faceplates.

In addition, he has quoted about $50 to $60 for making CNC upgraded aluminum faceplates if I would like to go down that path at any point in time. I've already purchased the bulk aluminum plate, but just I am waiting to make sure the faceplate design is exactly as desired before I pay for the CNC work.

Once I have the Audax mounted into the new faceplates and mounted back into the KEF 102 then I will update this thread about the SQ and fit accordingly.

Thanks

Don