Take the speaker/driver out and rotate it 180 degrees it may settle down this is the usual advice for voice coils rubbing, all speakers sag with time and lack of use.
Quick fix? Don’t go blasting them straight away may help if you do both at same time.
Quick fix? Don’t go blasting them straight away may help if you do both at same time.
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Right, rotating the woofer had no obvious effect. I think it'd take rather a long time to see this work based on the time it has apparently taken this to happen in the first place. Who knows though, I lost patience either way! 😀
So, in I went with the scalpel...took the dust cap off the offending woofer, checked the VC - looks good from what I can see (never looked at a VC before, but know what a damaged coil should look like). Definite rubbing to one side, so I shimmed with strips of A4 paper (three pieces thick on the offending side, one piece thick elsewhere at about 0.1mm per piece), biasing the VC away from the tight spot and then using laboratory-grade acetone, dampened the spider all over with it. Let it dry and repeated.
I guess most know how this works, but in case not, the binding resin that is used to consolidate the weave of the spider is softened by the acetone. As the acetone evaporates, this allows the resin to re-harden, and by biasing it during this process it (hopefully) permanently deforms the spider very slightly, thus puling the VC close to back on centre.
Seemingly this has been successful, but time and giving the speakers good workout will show whether it's been a complete success. Initial results are promising, though. Next step in a week or so will be to glue the dust cap back on with something semi-flexible and soft enough to remove should it happen again.
These old beasts can really sing!
So, in I went with the scalpel...took the dust cap off the offending woofer, checked the VC - looks good from what I can see (never looked at a VC before, but know what a damaged coil should look like). Definite rubbing to one side, so I shimmed with strips of A4 paper (three pieces thick on the offending side, one piece thick elsewhere at about 0.1mm per piece), biasing the VC away from the tight spot and then using laboratory-grade acetone, dampened the spider all over with it. Let it dry and repeated.
I guess most know how this works, but in case not, the binding resin that is used to consolidate the weave of the spider is softened by the acetone. As the acetone evaporates, this allows the resin to re-harden, and by biasing it during this process it (hopefully) permanently deforms the spider very slightly, thus puling the VC close to back on centre.
Seemingly this has been successful, but time and giving the speakers good workout will show whether it's been a complete success. Initial results are promising, though. Next step in a week or so will be to glue the dust cap back on with something semi-flexible and soft enough to remove should it happen again.
These old beasts can really sing!
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Right, after less than a day, the rubbing came back. I gave it another go and it came back a second time.
By this point it was all or bust, so I re-shimmed and broke out the heat gun. The woofer cones on my speakers are bonded to the surrounds and then a butyl (or similar) finishing has been applied over the joint between these parts at the factory. This finishing has started to come away slightly over the 25 years of the speakers life, and as such the surround was unevenly tensioned in the radial direction (a bit like a poorly setup bike wheel), thus it was being pulled to one side and rubbing.
So, armed with the heat gun on the low setting, about 6" away from the surround, I let rip and got it quite hot. The idea here being that the woofer surround is softened and re-set once cooled whilst biased by the shims. This has worked and the woofer has been fine for over a week. The dust cap was bonded back on using Unibond Serious glue (very good stuff), and all is well.
Job seemingly done!
By this point it was all or bust, so I re-shimmed and broke out the heat gun. The woofer cones on my speakers are bonded to the surrounds and then a butyl (or similar) finishing has been applied over the joint between these parts at the factory. This finishing has started to come away slightly over the 25 years of the speakers life, and as such the surround was unevenly tensioned in the radial direction (a bit like a poorly setup bike wheel), thus it was being pulled to one side and rubbing.
So, armed with the heat gun on the low setting, about 6" away from the surround, I let rip and got it quite hot. The idea here being that the woofer surround is softened and re-set once cooled whilst biased by the shims. This has worked and the woofer has been fine for over a week. The dust cap was bonded back on using Unibond Serious glue (very good stuff), and all is well.
Job seemingly done!
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