This driver was damaged in an earthquake decades ago. It made an audible distorted sound only with loud piano music. The driver was replaced with a new one. It appears that some paint has been scaped off. I don't see any cracks or dents. Is it possible to repair this tweeter?
Check if the magnet of the T27 was dislodged. It is a very common issue of t27. The magnet was just held by glue.
if so, you can peel off the cone carefully using razer. Alcohol can soft the glue between the cone and the plate. By the way, first check the resistance first and see if any anomality before any action.
Odd, there never were voice coil/cone replacement for those old Kef drivers that were distributed everywhere
I never knew if those Kef tweeters were made by Audax. Anyway I am not aware of cone/voice coil that match the patern of the motors (three holes often iirc).
The refurbishing must be done very carefully as you have a chance to reak the thin wires that ends the voice coils through the motor binding post. The voice coil in the one I knew had doube taped mounted voice coil on the motor you should be prudent when removong (because the thin wires).
Most of the time they lack some of the shelac on the dome. Maybe Planet 10 has some sauces receips for refurbishing the domes. However it has Ferro fluid so the top has to be removed to clean the dryed FF.... FF of the Kefs was low grade : very fluid FF.
The refurbishing must be done very carefully as you have a chance to reak the thin wires that ends the voice coils through the motor binding post. The voice coil in the one I knew had doube taped mounted voice coil on the motor you should be prudent when removong (because the thin wires).
Most of the time they lack some of the shelac on the dome. Maybe Planet 10 has some sauces receips for refurbishing the domes. However it has Ferro fluid so the top has to be removed to clean the dryed FF.... FF of the Kefs was low grade : very fluid FF.
you need a sweep with a impedance jig box to have the impedance measurement curve according the frequency. The datasheet says what is the minimum usable impedance: somthing 7.1 ohms at 1 k hz, but better to check on line datasheets.
Anyway, if the motor and voice coil are not damaged it is just needing a FF cleaning with alcohool and some re veenering with shelac on the dome if not damaged. Will be sligthy different than the genuine brandnew but the best you can doo if you want to keep the original.
Anyway, if the motor and voice coil are not damaged it is just needing a FF cleaning with alcohool and some re veenering with shelac on the dome if not damaged. Will be sligthy different than the genuine brandnew but the best you can doo if you want to keep the original.
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KEF made them.
I have peeled of the dome/butterfly on a few T27. As long as you go slow and are careful it is not hard. We must have gotten the butterflies somewhere but sometimes i did it just to ush dents out.
dave
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I saw two 33 units in a refurbishing, one cone was still hard when you push it with a finger, the other was easily bonding cause the lack of the stiff shelac... I do not know if it can help the op to check.
My T27 with similar age has a resistance 6R9 so it is pretty close. High chance no short or burn.
If so, it is a physical damage mostly if the sound is not right.
I still suspect the magnet is dislodged. Please be noted that the magnet still hold very strong to the faceplate. I have one T27 has the dislodged magnet issue. It was still making sound but distorted. I didnt know at first. But when I separated the diaphragm/voice coil. The coil just stuck in the gap. Eventually, I need to replace the voice coil. And yes you can just replace the coil. Search Ebay and find a tweeter replace diaphragm with similar size from China.(I did the replacement few years ago and cant have a right link for you). It costs me just few dollars. I removed the diaphragm from the new tweeter and glue it to the original t27 diaphragm. The sound is surprisingly close to original and I did the measure.
I suggest to measure the distance between the rim of the tweeter and the magnet. It may give you an idea .
yrs,
Leo
If so, it is a physical damage mostly if the sound is not right.
I still suspect the magnet is dislodged. Please be noted that the magnet still hold very strong to the faceplate. I have one T27 has the dislodged magnet issue. It was still making sound but distorted. I didnt know at first. But when I separated the diaphragm/voice coil. The coil just stuck in the gap. Eventually, I need to replace the voice coil. And yes you can just replace the coil. Search Ebay and find a tweeter replace diaphragm with similar size from China.(I did the replacement few years ago and cant have a right link for you). It costs me just few dollars. I removed the diaphragm from the new tweeter and glue it to the original t27 diaphragm. The sound is surprisingly close to original and I did the measure.
I suggest to measure the distance between the rim of the tweeter and the magnet. It may give you an idea .
yrs,
Leo
Can you please elaborate? I am too scared of causing damage on mine
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1mm is the gap distance !! and it may be or may not the magnet had been dislodged. I may take one of my t27 and make a measure. give me some time. or you can also make a measure of your the other t27.
May try the suggestion from diyiggy, re veneering the dome with shellac. it is the most easiest and you can try the result. You may also try a black nail polish to cover the scratched area (not the whole dome) and see the result.
T27 is not a ferro fluid cooling tweeter. (T33 on 104/2, however, is a ferrofluid cooling tweeter and most of them need to be refill or replaced).
T27 is my favourite tweeter even though it is not the top-notched tweeter nowadays. But with a good crossover design it sing beautifully. Indeed I have four pairs of speakers having T27 with different age. The newest t27s I have are from falcon.
May try the suggestion from diyiggy, re veneering the dome with shellac. it is the most easiest and you can try the result. You may also try a black nail polish to cover the scratched area (not the whole dome) and see the result.
T27 is not a ferro fluid cooling tweeter. (T33 on 104/2, however, is a ferrofluid cooling tweeter and most of them need to be refill or replaced).
T27 is my favourite tweeter even though it is not the top-notched tweeter nowadays. But with a good crossover design it sing beautifully. Indeed I have four pairs of speakers having T27 with different age. The newest t27s I have are from falcon.
Thanks for the info LeoJar. I will double check the measurements. It measured nearly perfectly one way, and the right angle to that was a little over 1mm off. We changed the crossover to the CS1 xover with upgraded poly caps for the tweeter, and thought it sounded much better than stock. It is a simpler circuit and doesn't have the protection circuit.
First you need to push the wires up thru the gromments. The glue that holds the butterfly is sort of like a post it. Get something thin and fairly robust under the edge and lift carefully, you may have to go around the edge slowly. You do not want to introduce any significant angle as you pull it off so as not to damage the VC.
If it is locked tight you have a broken magnet and the VC will be solidly by the shifted magnet.
dave
If it is locked tight you have a broken magnet and the VC will be solidly by the shifted magnet.
dave
there should be perhaps some dome parts from Morel or AUdax that fit those old Kef but certainly need to align new holes for the plate to fit the motor.
Often the no name swap parts have not the good voice coil depth or the wirering of the coil at the good heigth... it is risky.
I stilll like the D26 silk tweeter if I remember the name correctly of the old B&W as well ! 🙂 can sing with the good slope and crossing...
Often the no name swap parts have not the good voice coil depth or the wirering of the coil at the good heigth... it is risky.
I stilll like the D26 silk tweeter if I remember the name correctly of the old B&W as well ! 🙂 can sing with the good slope and crossing...