I have some very nice 1970s Celestion Ditton 44s with the wonderful T1600 12" bass drivers.
They have worked flawlessly (and superbly) for 40 years until this week, when one of them has rather suddenly developed a coil rub fart noise.
I have tried turning the speaker upside down, pressing here and there to try and eliminate the noise, so to weight the speaker in such a way that it reduces the fart, but really, I am looking for performing an overhaul at this stage.
I do have some experience of speaker cone rubber replacement, from when I replaced the rubbers on 16 midrange drivers from some Bose 801 midrange cabs back in the day. I was 100% successful in that case, in centralising the drivers.
Is it possible that I could carefully remove the cone, straighten any irregularity in the coil, and replace the rubber surround, thereby allowing me to straighten the coil in the magnet slot?
Any advice would be gratefully received.
They have worked flawlessly (and superbly) for 40 years until this week, when one of them has rather suddenly developed a coil rub fart noise.
I have tried turning the speaker upside down, pressing here and there to try and eliminate the noise, so to weight the speaker in such a way that it reduces the fart, but really, I am looking for performing an overhaul at this stage.
I do have some experience of speaker cone rubber replacement, from when I replaced the rubbers on 16 midrange drivers from some Bose 801 midrange cabs back in the day. I was 100% successful in that case, in centralising the drivers.
Is it possible that I could carefully remove the cone, straighten any irregularity in the coil, and replace the rubber surround, thereby allowing me to straighten the coil in the magnet slot?
Any advice would be gratefully received.
It is barely possible, I have done it a couple times out of sheer necessity as in absolute impossibility of getting same cones in Argentina, yet needing to preserve them, BUT: the potential for failure is high (even in my case with over 40 years of experience of building/repairing speakers) because speakers are NOT designed to be taken again and reassembled, parts are glued together, and are made of very weak materials: paper and cloth, so even if you redissolve adhesives they can be still be torn apart or at least deformed.
I have had some success with really old speakers, think 50´s and early 60´s Jensen and similar Guitar speakers because way back then "everything" was glued with infamous "speaker cement" , just thick Nitro (cellulose) dissolved in car paint thinner, so a few drops applied all around, put inside a plastic bag so it does not evaporate so fast, repeat every 15 minutes for a few hours 😱 would eventually soften it and allow spider/VC/cone assembly to be more or less safely pulled away from frame and magnet.
Now on more modern speakers, adhesives are harder to impossible to redissolve so ....
Since they are already damaged and ready for reconing anyway, you might try a cure-or-kill treatment: carefully cut dustcaps away without damaging anything else, blow in the exposed VC gap without removing it of course to put any dirt particle wandering there safely away, and insert between VC and polepiece a shim made out of *thin* aluminum, maybe you can cut one out of the side of a beer can, it will also be slightly curved which helps you, be careful to sand (well away from the speaker) any raised burr you might have on its edges, and move it all around the VC gap trying to sweep any dust particle away or straighten any bubble inside which might be scratching.
Do it a couple times, always with speaker pointing 45 degress downwards and blowing often, so any debris falls out instead of going deeper.
IF succesful (think you have about 50% chance, not bad), reglue dustcap in place with a bead of adhesive all around, you may use contact cement or Elmer´s white carpenters glue.
Instead of aluminum you can cut your shim out of 0.1 t0 0.125mm thick Mylar or acetate sheet, or 2 thicknesses od old X Ray film, a single thickness will be usually too thin.
Do no use paper or cardboard, it´s weak and you may leave pieces of it inside the gap
I have had some success with really old speakers, think 50´s and early 60´s Jensen and similar Guitar speakers because way back then "everything" was glued with infamous "speaker cement" , just thick Nitro (cellulose) dissolved in car paint thinner, so a few drops applied all around, put inside a plastic bag so it does not evaporate so fast, repeat every 15 minutes for a few hours 😱 would eventually soften it and allow spider/VC/cone assembly to be more or less safely pulled away from frame and magnet.
Now on more modern speakers, adhesives are harder to impossible to redissolve so ....
Since they are already damaged and ready for reconing anyway, you might try a cure-or-kill treatment: carefully cut dustcaps away without damaging anything else, blow in the exposed VC gap without removing it of course to put any dirt particle wandering there safely away, and insert between VC and polepiece a shim made out of *thin* aluminum, maybe you can cut one out of the side of a beer can, it will also be slightly curved which helps you, be careful to sand (well away from the speaker) any raised burr you might have on its edges, and move it all around the VC gap trying to sweep any dust particle away or straighten any bubble inside which might be scratching.
Do it a couple times, always with speaker pointing 45 degress downwards and blowing often, so any debris falls out instead of going deeper.
IF succesful (think you have about 50% chance, not bad), reglue dustcap in place with a bead of adhesive all around, you may use contact cement or Elmer´s white carpenters glue.
Instead of aluminum you can cut your shim out of 0.1 t0 0.125mm thick Mylar or acetate sheet, or 2 thicknesses od old X Ray film, a single thickness will be usually too thin.
Do no use paper or cardboard, it´s weak and you may leave pieces of it inside the gap
Bravo! It worked a charm!
I carefully cut away the dust cap, to reveal a cardboard tube around the pole. In my case I could push outwards the speaker cone, as it has a huge range of movement thanks to fat rubbers with a lot of stretch in them, to reveal the entire surface of the cardboard tube.
The gap was consistent all around, but there were 3 or 4 places where there was a small spot of a substance, like glue or doping or paint or something for treating loudspeakers from when it was manufactured, that was clearly scraping the pole. How they had avoided scraping for 40 years, I'll never know!
I used my scalpel to carefully remove them, and a 240 grit black (wet & dry) nail file to smooth them out, making sure not to let any debris fall into the crack.
Eventually, it was as clean as a whistle and all rubbing was gone, totally gone!
Thanks so much! I hope your economy recovers, and that we return the Falklands!
Bless you brother for taking the time to help me with such expertise!
Lucas
I carefully cut away the dust cap, to reveal a cardboard tube around the pole. In my case I could push outwards the speaker cone, as it has a huge range of movement thanks to fat rubbers with a lot of stretch in them, to reveal the entire surface of the cardboard tube.
The gap was consistent all around, but there were 3 or 4 places where there was a small spot of a substance, like glue or doping or paint or something for treating loudspeakers from when it was manufactured, that was clearly scraping the pole. How they had avoided scraping for 40 years, I'll never know!
I used my scalpel to carefully remove them, and a 240 grit black (wet & dry) nail file to smooth them out, making sure not to let any debris fall into the crack.
Eventually, it was as clean as a whistle and all rubbing was gone, totally gone!
Thanks so much! I hope your economy recovers, and that we return the Falklands!
Bless you brother for taking the time to help me with such expertise!
Lucas
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