I've just obtained a lovely pair of Goodmans Magnum K2 speakers, which are 3 way, and with large bass drivers.
When I've taken a good look at the bass drivers it looks like the plastic (shiny and black) coating has started to delaminate around the dust cap area, which is not good. Although they still sound really good.
Is there an easy/simple way to resolve this?
My first thought was to see if I could gently press it back against the cone material, and see if it would stick back again. However I think the plastic coating has shrunk, which is why it's delaminated. When you try and push it back, its tight.
My first idea is to put the speakers on their back, and using a heat gun see if I could gently stretch it, and possibly get it to stick down. This would be by keeping the gun constantly moving and gradually increasing the heat until it makes the plastic malleable.
However "before" attempting this, I thought I'd reach out to the combined wisdom on this forum and see if there's a better way to do this, or easier.
I know I could maybe try re coning them, or get them re coned, but I'd rather do a fix if I can.
Please see attached pictures.
Thanks, Rob
When I've taken a good look at the bass drivers it looks like the plastic (shiny and black) coating has started to delaminate around the dust cap area, which is not good. Although they still sound really good.
Is there an easy/simple way to resolve this?
My first thought was to see if I could gently press it back against the cone material, and see if it would stick back again. However I think the plastic coating has shrunk, which is why it's delaminated. When you try and push it back, its tight.
My first idea is to put the speakers on their back, and using a heat gun see if I could gently stretch it, and possibly get it to stick down. This would be by keeping the gun constantly moving and gradually increasing the heat until it makes the plastic malleable.
However "before" attempting this, I thought I'd reach out to the combined wisdom on this forum and see if there's a better way to do this, or easier.
I know I could maybe try re coning them, or get them re coned, but I'd rather do a fix if I can.
Please see attached pictures.
Thanks, Rob
Attachments
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You may have seen this K2 bass driver cone rescue, which involves the use of a heat gun:
Goodmans Magnum K2 - SL cone rescue - diyAudio
Goodmans Magnum K2 - SL cone rescue - diyAudio
Sounds like I'm on the right track 🙂
There's no mention of what heat setting was used, so I will start low and keep it moving around so as not to get anything too hot and melt it. I've seen the dust covers slide down like the photos on the blog, I wondered what caused it, but it probably is heat and gravity.
I will try doing the same as in the blog. I have some Granville black silicone sealant that was recommended on this forum (Galu I think?) for doing speaker re foams, so I'll use that to put the dust cap back on.
I had another idea whilst I was out walking - I wonder if you removed the dust cap, then put the speaker in a (low) pre heated oven with say a bag of flour (or similar) in the cone if that would work too? The bag the flour was in would have to be a bit heat resistant, and able to move with the flour. Hopefully you wouldn't need much heat at all, and as it heated up the contents of the bag would push the membrane down slowly against the cone and allow it to stick back in place. You could then remove the bag and push a bit more on the membrane to get it to stick even better. Then put the dust cap back on with the sealant (or similar) that I mentioned.
I think I'll go with the heat gun method though, as it is hopefully more controllable, and I can see what is going on all the time.
Thanks, Rob
There's no mention of what heat setting was used, so I will start low and keep it moving around so as not to get anything too hot and melt it. I've seen the dust covers slide down like the photos on the blog, I wondered what caused it, but it probably is heat and gravity.
I will try doing the same as in the blog. I have some Granville black silicone sealant that was recommended on this forum (Galu I think?) for doing speaker re foams, so I'll use that to put the dust cap back on.
I had another idea whilst I was out walking - I wonder if you removed the dust cap, then put the speaker in a (low) pre heated oven with say a bag of flour (or similar) in the cone if that would work too? The bag the flour was in would have to be a bit heat resistant, and able to move with the flour. Hopefully you wouldn't need much heat at all, and as it heated up the contents of the bag would push the membrane down slowly against the cone and allow it to stick back in place. You could then remove the bag and push a bit more on the membrane to get it to stick even better. Then put the dust cap back on with the sealant (or similar) that I mentioned.
I think I'll go with the heat gun method though, as it is hopefully more controllable, and I can see what is going on all the time.
Thanks, Rob
I have had some of those lovely woofers. Hopefully Galu’s video helps. I expect how to fix depends on whether it is the coating peeling off or the actual cone delaminating.
dave
dave
That was, indeed, my recommendation for helping to seal tears in PVC speaker surrounds, and it would be ideal for re-attaching the dust cap to the plastic woofer coating.
I'm not so keen on your 'oven-ready' idea though, as the weight of flour necessary to do the job may damage the cone suspension. Also, the loudspeaker magnet may lose some strength if heated significantly above room temperature
In the latter case, a thin, bonding layer of the Granville sealant and adhesive may be the answer.
This particular product dries to a flexible, rubber like consistency - not to be confused with other silicone sealants.
Granville Black Silicone Sealant 40g | Halfords UK
All sorted now - see attached pictures.
First picture shows how the shiny black plastic had delaminated from the cone, and has pushed the dust cover outwards.
The second picture is after applying a heat gun on the low power setting, and set at 110oC, to the effected area, and carefully pushing it back into place a bit at a time. Then applying some Granville black silicone sealant around the shiny edge, and the paper cone - to hopefully help it to stay in place.
Third picture shows the completed job with the domed dust cover glued back in the correct central place, again with the same Granville sealant.
I'm pretty happy with how this has turned out, and it wasn't difficult you just have to take it slow and easily.
Rob
First picture shows how the shiny black plastic had delaminated from the cone, and has pushed the dust cover outwards.
The second picture is after applying a heat gun on the low power setting, and set at 110oC, to the effected area, and carefully pushing it back into place a bit at a time. Then applying some Granville black silicone sealant around the shiny edge, and the paper cone - to hopefully help it to stay in place.
Third picture shows the completed job with the domed dust cover glued back in the correct central place, again with the same Granville sealant.
I'm pretty happy with how this has turned out, and it wasn't difficult you just have to take it slow and easily.
Rob