Yamaha Sub cone repair - UK Vintage Radio Repair and Restoration Discussion Forum

Grubhead · 30th Sep 2020, 1:04 pm

I have a Yamaha YST-SW40 Subwoofer unit, which was make nasty rattling sounds during loud bass sounds in movies. I discovered on removing the front of the unit and the speaker unit, although the cone looks OK that the rubber outer ring has separated from the black "card" section for about 10cm round the edge!
I don't believe the speaker unit is still made, it's about 50 watts and is 6 ohms. It has the number XQ840A0 on it.

Just wondering if it could be glued back? And if so what glue to use?
There is no gap in the tear. It looks like it's still joined until you push the cone.

I have ordered a new sub unit, but it's been a good sub and if it can be repaired then I will do it.

Edward Huggins · 30th Sep 2020, 1:41 pm

Yes, use Evostick or any adhesive that does not set hard. No real need to buy another!

ajgriff · 30th Sep 2020, 4:53 pm

As Edward says a perfectly good repair should be possible. The only thing I'm unsure about is whether or not Evo-Stik (or similar) would be up to the task, especially given the excursions endured by a sub-woofer's cone. For what it's worth I repaired a bass dirver with the same issue using Unibond Repair Extreme (20g) a while back with great success. If you'd like the repair to be relatively invisible it's best to remove the driver and apply the glue from the rear. Repair Extreme is really strong, adheres well and retains a degree of flexibilty when set. The only thing to be aware of is that once the tube is opened the unused glue cures within a few weeks so it's best to have a few jobs lined up around the same time if you can.

Alan

Grubhead · 30th Sep 2020, 8:15 pm

Thanks for the replies. Can you be more specific on the Evo-Stik type? I have some Evo-Stik wood glue. Bostik Solvent Free, in stock. Will they do the trick?

ajgriff · 30th Sep 2020, 8:58 pm

Evo-Stik wood glue is a conventional PVA formulation and Bostik solvent free is water based PVA. I think either if of these would only work if reinforced with thin paper or tissue since we're dealing with a tear. There is then a risk of changing the cone's sonic characteristics although probably not that significantly. Adhesion to the rubber if needed could also be a problem. Longevity at high power could be an issue too. I might be wrong but I think Edward was thinking of Evo-Stik contact adhesive.

Alan

Outrun_uk · 30th Sep 2020, 9:16 pm

I used Evo-Stik contact adhesive on a Mission speaker cone which had become seperated, rubber to polypropylene (?). Worked absolutely fine for a few years until I upgraded the speakers. Also used PVA in the past but that was on a paper cone.

Kev

ajgriff · 30th Sep 2020, 9:42 pm

PVA will be fine if there's an overlap between the rubber surround and the cone. However, my understanding is that this is actually a tear in the paper cone adjacent to the surround.

Alan

Diabolical Artificer · 1st Oct 2020, 6:05 am

EvoStik wood glue should be fine - I've used watered down PVA and tissue paper to fix a fist sized hole in an 18" sub - worked well. I think I still have some "proper" glue somewhere that came with a re-cone kit you can have if you want it for the postage - £3.10, drop us a PM if interested..

Andy.

BulgingCap · 1st Oct 2020, 8:31 am

I think Grubhead means that the suspension ring has come unbonded from the cone in one place, rather than being torn.
'Copydex' used to be recommended, but I have no access to it now so have successfully used pressure sensitive carpet tile adhesive (mainly because I have a humungous tub of it) on a good number of ring replacements, including my Allison 4s which have had a good thrashing for years and are still fine.
BC

Grubhead · 2nd Oct 2020, 9:18 pm

I do have a tube of Evo Impact now. Just have to wait to go outside to glue it using that method if it will be OK.
In the meantime I have photo the cone, I put on some green acrylic paint to show the area damage, though it only comes away when pressed.
Comments about Evo stick on Amazon seem to imply that the glue doesn't take to rubber to well. And since part of the problem is the rubber ring, that concerns me.

PS it is only the rubber that has torn, there is thin piece of the rubber still on the cone.

BulgingCap · 5th Oct 2020, 6:39 am

Ah, I see now - that doesn't look too good. If that was mine I would replace the whole 'ring' as it is neither expensive nor difficult. I think any repair will fail due to the air pressure during cone excursions. It looks as if the 'ring' is bonded to the back of the paper cone - sometimes it is the front, sometimes the back, and sometimes the ring is concave and sometimes convex - no difference with replacement technique. 'Contact' adhesive will make any ring replacement difficult if not impossible. It is best to use some kind of glue that will allow a bit of re-alignment before it goes off ie time to ease the cone in and out to make sure it isn't binding.
BC

ajgriff · 5th Oct 2020, 1:08 pm

I agree with BC as it looks like the rubber is starting to perish. Dilute PVA is the usual recommendation for use when replacing surrounds. It's probably worth replacing the surround on the other bass driver(s) at the same time.

Alan

Grubhead · 8th Oct 2020, 12:30 pm

Further examination has revealed a second tear in the rubber section mirroring the first at the other side, probably about the same size!
I have seen the replacement rubber units on E-Bay, but although they are cheap less than £3! As they are from China will take ages to arrive too. I also don't fancy trying to take off the old one. It's looks well sealed down around the outer edge. And I fear that removing it from the paper cone too, could cause the cone to catch inside the magnets. I had a speaker like that before with a cone that scraped and despite many attempts to cure it - all failed.

I have seen a new speaker unit on Amazon, though not a match with the old one, should bring it to life again. That's coming in the next few days.
Thanks for the advice everyone.

Radio Wrangler · 8th Oct 2020, 1:30 pm

Replacing rubber surrounds is actually quite easy. I had a pair of Peerless K040MRF units to do. There is virtually no chance of finding another pair of these in good condition, so I had a go. Rings were found from a firm in Holland who do an immense range. I bought glue from then assuming it ought to be a good match.

The only tool I used was a scalpel, and a few bits of wire to shim the voice coil. It took me an evening to do both. Left them a day to cure and back they went. The speakers are open fronted, the surround rings are on full display. It all sounds right and looks right. I'm 100% happy and it was my first attempt.

Fine on finding another driver, even if not the exact type.... so why not shop around for a more confidence-inspiring European or American source and have a go at the old unit?

Then, if the new driver isn't as good as you'd like, you have a fall back.

Memory of what things sound like is notoriously fickle, so having one restored to original condition to compare against will protect you from creeping dissatisfaction.

David

Edward Huggins · 8th Oct 2020, 8:13 pm

Does the new driver unit you've ordered have the same resonant frequency as that in the Yamaha? If not, it may be prone to back pressure issues and deliver a "one note" bass.
I still suggest you have a go with bonding the Yamaha cone to the original surround using the recommended adhesive/s as advised here. You've nothing to loose!

30th Sep 2020, 1:04 pm	#1
Grubhead Heptode Join Date: Dec 2016 Location: Sheffield, South Yorkshire, UK. Posts: 539	Yamaha Sub cone repair I have a Yamaha YST-SW40 Subwoofer unit, which was make nasty rattling sounds during loud bass sounds in movies. I discovered on removing the front of the unit and the speaker unit, although the cone looks OK that the rubber outer ring has separated from the black "card" section for about 10cm round the edge! I don't believe the speaker unit is still made, it's about 50 watts and is 6 ohms. It has the number XQ840A0 on it. Just wondering if it could be glued back? And if so what glue to use? There is no gap in the tear. It looks like it's still joined until you push the cone. I have ordered a new sub unit, but it's been a good sub and if it can be repaired then I will do it.

30th Sep 2020, 1:41 pm	#2
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,338	Re: Yamaha Sub cone repair Yes, use Evostick or any adhesive that does not set hard. No real need to buy another! __________________ Edward.

30th Sep 2020, 4:53 pm	#3
ajgriff Nonode Join Date: May 2004 Location: Halifax, West Yorkshire, UK. Posts: 2,587	Re: Yamaha Sub cone repair As Edward says a perfectly good repair should be possible. The only thing I'm unsure about is whether or not Evo-Stik (or similar) would be up to the task, especially given the excursions endured by a sub-woofer's cone. For what it's worth I repaired a bass dirver with the same issue using Unibond Repair Extreme (20g) a while back with great success. If you'd like the repair to be relatively invisible it's best to remove the driver and apply the glue from the rear. Repair Extreme is really strong, adheres well and retains a degree of flexibilty when set. The only thing to be aware of is that once the tube is opened the unused glue cures within a few weeks so it's best to have a few jobs lined up around the same time if you can. Alan

30th Sep 2020, 8:15 pm	#4
Grubhead Heptode Join Date: Dec 2016 Location: Sheffield, South Yorkshire, UK. Posts: 539	Re: Yamaha Sub cone repair Thanks for the replies. Can you be more specific on the Evo-Stik type? I have some Evo-Stik wood glue. Bostik Solvent Free, in stock. Will they do the trick?

30th Sep 2020, 8:58 pm	#5
ajgriff Nonode Join Date: May 2004 Location: Halifax, West Yorkshire, UK. Posts: 2,587	Re: Yamaha Sub cone repair Evo-Stik wood glue is a conventional PVA formulation and Bostik solvent free is water based PVA. I think either if of these would only work if reinforced with thin paper or tissue since we're dealing with a tear. There is then a risk of changing the cone's sonic characteristics although probably not that significantly. Adhesion to the rubber if needed could also be a problem. Longevity at high power could be an issue too. I might be wrong but I think Edward was thinking of Evo-Stik contact adhesive. Alan

30th Sep 2020, 9:16 pm	#6
Outrun_uk Heptode Join Date: Aug 2009 Location: Liverpool, Merseyside, UK. Posts: 705	Re: Yamaha Sub cone repair I used Evo-Stik contact adhesive on a Mission speaker cone which had become seperated, rubber to polypropylene (?). Worked absolutely fine for a few years until I upgraded the speakers. Also used PVA in the past but that was on a paper cone. Kev

30th Sep 2020, 9:42 pm	#7
ajgriff Nonode Join Date: May 2004 Location: Halifax, West Yorkshire, UK. Posts: 2,587	Re: Yamaha Sub cone repair PVA will be fine if there's an overlap between the rubber surround and the cone. However, my understanding is that this is actually a tear in the paper cone adjacent to the surround. Alan

1st Oct 2020, 6:05 am	#8
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,667	Re: Yamaha Sub cone repair EvoStik wood glue should be fine - I've used watered down PVA and tissue paper to fix a fist sized hole in an 18" sub - worked well. I think I still have some "proper" glue somewhere that came with a re-cone kit you can have if you want it for the postage - £3.10, drop us a PM if interested.. Andy. __________________ Curiosity hasn't killed this cat...so far.

1st Oct 2020, 8:31 am	#9
BulgingCap Pentode Join Date: Apr 2017 Location: South Coast, Western Australia. Posts: 129	Re: Yamaha Sub cone repair I think Grubhead means that the suspension ring has come unbonded from the cone in one place, rather than being torn. 'Copydex' used to be recommended, but I have no access to it now so have successfully used pressure sensitive carpet tile adhesive (mainly because I have a humungous tub of it) on a good number of ring replacements, including my Allison 4s which have had a good thrashing for years and are still fine. BC

2nd Oct 2020, 9:18 pm	#10
Grubhead Heptode Join Date: Dec 2016 Location: Sheffield, South Yorkshire, UK. Posts: 539	Re: Yamaha Sub cone repair I do have a tube of Evo Impact now. Just have to wait to go outside to glue it using that method if it will be OK. In the meantime I have photo the cone, I put on some green acrylic paint to show the area damage, though it only comes away when pressed. Comments about Evo stick on Amazon seem to imply that the glue doesn't take to rubber to well. And since part of the problem is the rubber ring, that concerns me. PS it is only the rubber that has torn, there is thin piece of the rubber still on the cone. Attached Thumbnails Last edited by Grubhead; 2nd Oct 2020 at 9:22 pm. Reason: PS added

5th Oct 2020, 6:39 am	#11
BulgingCap Pentode Join Date: Apr 2017 Location: South Coast, Western Australia. Posts: 129	Re: Yamaha Sub cone repair Ah, I see now - that doesn't look too good. If that was mine I would replace the whole 'ring' as it is neither expensive nor difficult. I think any repair will fail due to the air pressure during cone excursions. It looks as if the 'ring' is bonded to the back of the paper cone - sometimes it is the front, sometimes the back, and sometimes the ring is concave and sometimes convex - no difference with replacement technique. 'Contact' adhesive will make any ring replacement difficult if not impossible. It is best to use some kind of glue that will allow a bit of re-alignment before it goes off ie time to ease the cone in and out to make sure it isn't binding. BC

5th Oct 2020, 1:08 pm	#12
ajgriff Nonode Join Date: May 2004 Location: Halifax, West Yorkshire, UK. Posts: 2,587	Re: Yamaha Sub cone repair I agree with BC as it looks like the rubber is starting to perish. Dilute PVA is the usual recommendation for use when replacing surrounds. It's probably worth replacing the surround on the other bass driver(s) at the same time. Alan

8th Oct 2020, 12:30 pm	#13
Grubhead Heptode Join Date: Dec 2016 Location: Sheffield, South Yorkshire, UK. Posts: 539	Re: Yamaha Sub cone repair Further examination has revealed a second tear in the rubber section mirroring the first at the other side, probably about the same size! I have seen the replacement rubber units on E-Bay, but although they are cheap less than £3! As they are from China will take ages to arrive too. I also don't fancy trying to take off the old one. It's looks well sealed down around the outer edge. And I fear that removing it from the paper cone too, could cause the cone to catch inside the magnets. I had a speaker like that before with a cone that scraped and despite many attempts to cure it - all failed. I have seen a new speaker unit on Amazon, though not a match with the old one, should bring it to life again. That's coming in the next few days. Thanks for the advice everyone.

8th Oct 2020, 1:30 pm	#14
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,901	Re: Yamaha Sub cone repair Replacing rubber surrounds is actually quite easy. I had a pair of Peerless K040MRF units to do. There is virtually no chance of finding another pair of these in good condition, so I had a go. Rings were found from a firm in Holland who do an immense range. I bought glue from then assuming it ought to be a good match. The only tool I used was a scalpel, and a few bits of wire to shim the voice coil. It took me an evening to do both. Left them a day to cure and back they went. The speakers are open fronted, the surround rings are on full display. It all sounds right and looks right. I'm 100% happy and it was my first attempt. Fine on finding another driver, even if not the exact type.... so why not shop around for a more confidence-inspiring European or American source and have a go at the old unit? Then, if the new driver isn't as good as you'd like, you have a fall back. Memory of what things sound like is notoriously fickle, so having one restored to original condition to compare against will protect you from creeping dissatisfaction. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

8th Oct 2020, 8:13 pm	#15
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,338	Re: Yamaha Sub cone repair Does the new driver unit you've ordered have the same resonant frequency as that in the Yamaha? If not, it may be prone to back pressure issues and deliver a "one note" bass. I still suggest you have a go with bonding the Yamaha cone to the original surround using the recommended adhesive/s as advised here. You've nothing to loose! __________________ Edward.