I have several small "woofers" to refoam that have a paper cone coated with a softer, slightly tacky layer. I've peeled away the rotted foam but it leaves a very narrow edge of exposed paper, with a slight 'lip' where the coating starts that I think would interfere with the new adhesive. If I try to expose more paper it tends to want to peel off too much. Abrading the coating only damages the paper beneath.
What's the correct technique?
These are Morel MW-160 units.
NLA and too expensive to replace without first trying to repair them.
What's the correct technique?
These are Morel MW-160 units.
NLA and too expensive to replace without first trying to repair them.
Can't you just clean it as much as possible, and then use a small brush to brush on glue where it's "bad" to bond the surface?
There isn't a surround made for this exact size driver and I'm concerned the foam will overlap the ridge where the coating starts, preventing contact with the paper margin.
The typical adhesive I used the only other time I attempted to refoam woofers looked like ordinary Elmer's white glue. Pretty weak stuff, and there's no way to clamp it.
The typical adhesive I used the only other time I attempted to refoam woofers looked like ordinary Elmer's white glue. Pretty weak stuff, and there's no way to clamp it.
This is where I'm at today.
The coating was applied over the edge of the old foam so when that was pulled up it left the tattered edge of coating pulled up, with ~4mm margin of exposed paper.
The cone is straight-sided...i will need to use a surround with an angled edge. And I may have to cut the surround to 'shrink' it to the correct diameter for this metric driver.
The coating was applied over the edge of the old foam so when that was pulled up it left the tattered edge of coating pulled up, with ~4mm margin of exposed paper.
The cone is straight-sided...i will need to use a surround with an angled edge. And I may have to cut the surround to 'shrink' it to the correct diameter for this metric driver.
I have the same issue with a pair of Celestion Ditton 12" woofers. I haven't attempted to glue the new surround yet, but did purchase the speaker glue used for polyprop cones as I was sure the white, PVA, glue wasn't going to work. You can get the other glue from Midwest Speaker Repair.
I believe I have that one in my eBay cart. Very cheap but I'm pretty sure it has a flat inner border and I don't have a flat landing on my cones.
I had a look on another Morel MW-160.
Quite gigantic surround!
I must be a existing "working one" somewhere
Quite gigantic surround!
I must be a existing "working one" somewhere
Here's an old photo of a pair I finished.
The surround isn't nearly as wide as the one you're showing, and the coating is applied to the inner margin of the foam as well.
... But that's not the issue. My question concerns HOW I deal with the rubber coating on the cone?
The surround isn't nearly as wide as the one you're showing, and the coating is applied to the inner margin of the foam as well.
... But that's not the issue. My question concerns HOW I deal with the rubber coating on the cone?
From your initial photo the treatment is not applied consistently over the foam edge, therefore this isn’t critical (or wasn’t well done originally).
I think trimming off the overlapping and now essentially useless treatment, to leave a consistent and fairly flat adhesion area, is the way to go. This may require tedious gentle pulling with pliers or tweezers and simultaneous cutting with a sharp blade or trimmer like a small carving tool. The cutting should prevent removal from the cone where the treatment should remain, obviously with care to not do damage and hopefully with nice aesthetics.
As to getting a replacement surround with correct angle and/or inner adhesion area, you may have to compromise.
I think trimming off the overlapping and now essentially useless treatment, to leave a consistent and fairly flat adhesion area, is the way to go. This may require tedious gentle pulling with pliers or tweezers and simultaneous cutting with a sharp blade or trimmer like a small carving tool. The cutting should prevent removal from the cone where the treatment should remain, obviously with care to not do damage and hopefully with nice aesthetics.
As to getting a replacement surround with correct angle and/or inner adhesion area, you may have to compromise.
It looks nothing like an original unrotted foam (#10 - a scan of a film photo I took ~35 years ago). I'm sure it's been replaced.
I'd sure prefer a narrow replacement if I can find one. Sellers don't make it easy.
Pricing is all over the place from $1.24 ea to over $15 ea.
I'd sure prefer a narrow replacement if I can find one. Sellers don't make it easy.
Pricing is all over the place from $1.24 ea to over $15 ea.
I read that Morel MW-160s become Morel MW-164s, with the rubber surround.
At least some of the white glues (or maybe all?) sold for speaker cone repairs is actually 'tacky' EVA, not PVA. Both PVA and EVA come in many formulations, but the EVA marketed for this purpose is quite thick and becomes tacky quite quickly so that you don't need to clamp the cone. It looks and smells the same as PVA.
Tacky EVA is pretty much perfect for the job because it can be cleaned up with water (this must be done very quickly; my first one was a bit messy as I took too long) and is very strong. I replaced rubber surrounds on composite poly cones and they are stuck FAST and will not separate! You apply the glue sparingly onto both surfaces, leave it a few minutes to go off a bit, then press them together. It's not like contact glue as you can adjust the fit for a few minutes. The only reason for the small wait before joining is to make sure the added tackiness causes the parts to stay together.
Note that I didn't buy speaker-specific glue, but researched for some time what is used and then just bought an appropriate general purpose fast tack EVA ('X-Press It Powertac' from a shop here in Australia called Spotlight). It worked much better than expected. This is an Australian made product, but any EVA that is advertised to have fast tackiness would probably be OK.
I'd imagine gluing foam surrounds onto paper cones would be easier than rubber onto plastic due to the nature of the materials.
That said, now that I've done it, I reckon Weldbond would do the job. It's very similar in tackiness and thickness to the stuff I used, even though it's a PVA.
Tacky EVA is pretty much perfect for the job because it can be cleaned up with water (this must be done very quickly; my first one was a bit messy as I took too long) and is very strong. I replaced rubber surrounds on composite poly cones and they are stuck FAST and will not separate! You apply the glue sparingly onto both surfaces, leave it a few minutes to go off a bit, then press them together. It's not like contact glue as you can adjust the fit for a few minutes. The only reason for the small wait before joining is to make sure the added tackiness causes the parts to stay together.
Note that I didn't buy speaker-specific glue, but researched for some time what is used and then just bought an appropriate general purpose fast tack EVA ('X-Press It Powertac' from a shop here in Australia called Spotlight). It worked much better than expected. This is an Australian made product, but any EVA that is advertised to have fast tackiness would probably be OK.
I'd imagine gluing foam surrounds onto paper cones would be easier than rubber onto plastic due to the nature of the materials.
That said, now that I've done it, I reckon Weldbond would do the job. It's very similar in tackiness and thickness to the stuff I used, even though it's a PVA.
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Any consideration or worry about centering the voice coil? Normally you would pull off the dust cap and shim the voice coil when replacing the foam. Does not seem to be so easy to do here.
I've only done this once--to 4 ordinary Peerless 12" woofers, using a kit that came with a new (oversized) dustcap.
That's not the case here. These 6" woofers have a 3" voicecoil. IF I could find a big-enough dustcap it would probably reach all the way to the surround 😯
I'm going to try to do it without shims & just hope the oversize spider keeps the coil & former centered in the gap.