Repair a hole in a speaker cone. PVA or CA?

[allante666]

So I have a speaker which someone has stabbed a couple of times with a screwdriver (not me I hasten to add, this was done purposely, at the same time as the hammer was taken to the rest of it! Would love to know its history!!). only small but want to repair them. I have sone spare speaker cone material I was going to glue a couple patches behind them but whats best to use? CA (superglue) or PVA? Ive seen both mentioned.

[Bill Moore]

I too am curious what the modern repair might be, I have used rubber cement, over a rolling paper patch. I try to align the existing cone material to it's original shape before applying the "patch".

[J M Fahey]

Hi.
First try to align the torn cone material the best you can, as Bill said.
Put a couple drops of PVA on either side of the tear, let it soak a couple minutes as to soften the cardboard and "comb" it towards the slit or hole with a brush, also soaked in PVA.
Original speaker cone cardboard is made of random-oriented cellullose fiber/paste + glue + (usually) black pigment (soot is light and very little goes a long way); that's why wetting paper weakens it.
You are trying to turn the torn part into a little bit of virgin paper paste again, and "sculpting" it into a seamless part of cone.
If not enough, take any old piece of paper cone you have around, mix it with a little PVA and maybe a couple drops of water, and use it to reinforce the torn part.
Simple puncture holes are easier.
Results will not be nice but will hold very well.
Let it sit at least overnight before treating it to the last "Cannibal Corpse Vampires" hit rendition on your maxxed Randall Warhead.
Cyano acrilate? : never (nor epoxy, etc), only water-based glues (PVA)

[Earl Norton]

I have used clear nail polish with good results.

[Mark Hammer]

While cones are intended to be relatively rigid, there is some degree of flexibility in them that is part of what provides their individual "personality", and anything which disturbs the symmetry and concentric aspects of stiffness and flexibility will tend to take away from that personality.

So, ultimately, what you want is something that does not impose more stiffness in one specific location than is true of the rest of the cone at that particular distance from the voice coil.

PVA, which JMF recommended, is something that comes up frequently in speaker-repair discussions, in conjunction with the tissue-paper patch. It dries a whole lot more flexible than superglue.

Since you want it to be both light and moderately flexible when it dries, dilute the PVA with a bit of water, so that you can "paint" it on. A thinner layer will allow it to both soak into the cone and patch, and also allow you to titrate the thickness appropriately. You may have to wait a little bit for each layer to dry, but better to be patient and have it be the right thickness, than impatient and have a thick blob sitting there in the cone.

[zero cool]

I don't know what PVA is but I use a type of white glue that is used for repairing speaker foam for the paper repair. I generally try and realign the paper back the exact way it was supposed to be and then apply a tiny amount of this white glue to both sides of the damaged area working it into the seems and trying to flatten the area as much as possible. sometimes i take a small metal object(s) like a socket from a socket set and use that to roll over the area or work the area flat as much as possible. then i let it stand overnight. the next day i will take a very very thin layer of silicone and go over the back of the repaired area just to damped any flexing or motions that might cause the repaired area to fail. this seems to work for small area's.

larger tears or holes are a bit more difficult to repair without it causing some alteration to the sound. any sort of glue that dries stiff will be problematic. clear silicone if applied carefully works but it is VERY messy to deal with and hard to work with to keep the amounts small and even and in the desired work area. But if you can manage to repair a large torn area with the stuff. it allows the paper to stay glued yet be flexible.

[Mark Hammer]

PVA is white glue. Also known as "Elmer's Glue". It is water soluble.

I didn't know they were one in the same, either.

[allante666]

Thanks for all the info guys, looks like pva is the way to go! fortunately the one i have only has a couple of screwdriver punctures in it so wont be bad to do. Its only an old Laney 200 but its more a challenge than a necessity, just got the top of the cabinet to replace and then its all done. not bad for a write off that had been attacked from all angles with a hammer. Amazingly the circuit boards were perfectly ok despite the front panel being hit hard enough to break seven pots clean off the circuit board! Im only doing it to sell so I dont have the inconvenience of a customer waiting for it to be finished! (been there, done that. ex tv engineer) Its all the more enjoyable when you can do it as and when you like

[J M Fahey]

Hi Allante, we deserve to see some pictures of that amp !!!
On an old PC repair book they showed the picture of a hard disk with three .357 Magnum shots.
The owner was really mad at it; only problem is that it contained all financial and operative information about his shop, and he took it to a Data "fisher" to reclaim as much as possible.
Maybe his son is the Laney 200 ex-owner !!

[allante666]

Yeah I wish I had taken some now. Ive repaired all the panelwork (15 years as a panelbeater has its uses!) Just waiting for a couple of pots on order to finish the circuit and just leaves me the cab top to do. I managed to get the tolex type covering off in one piece so am hoping to re use it as soon as i have made and shaped a new wood part.
Dont know if you can still access this but this is the ebay listing I bought it from. The photos dont actually show how bad the front panel is, most of the pots are not connected to anything and the panel is very badly bent and dented. the ebay number is 120539421031 if you can see it.
The rear panel is actually folded across the middle on the right hand side where the sockets are and is all bent around the heatsink.
Its been quite fun actually, it will be a shame to see it go when its done!
Ill post some pics when ive finished it.

[Mark Hammer]

I'm curious as to whether, in those cases where the cone is particularly light, and the tear particularly bad (necessitating a significant change in local weight in order to repair it), it is a reasonable idea to brush a little PVA at the same distance from the coil on other nondamaged parts of the cone, just to balance the weight so that the piston-like action of the cone is not thrown off by the repair. (think of it like wheel balancing)

In a hypothetical sense, this seems reasonable to me. But then, the change in weight, even with a substantial repair may be so slight as to have negligible impact on the proper movement of the cone and coil.

Opinions?

[J M Fahey]

Hi Mark. I won't even mention your surname because the poor Laney , on hearing it, cries and runs to hide behind the nearest furniture piece ,
I thought the same as you, but apparently the strong centering action of both spider and actual corrugated cone edge avoids it.
Even on a healthy speaker, both flexible wires plus adhesive needed to hold them tight to the cone, sit quite unbalanced on only one side of the cone, yet it works, so maybe in practice it is not that bad.
The case where I find the voice coil displaced and rubbing is either when the adhesive was applied *very* sloppily and along time (even months) it goes on drying slowly and "pulling" the voice coil towards one side, or when the cone gets wet and deforms.
There is an unrelated problem which amounts to the same: when the cabinet falls squarely on its back, the magnet unglues, shifts, and pinches the voice coil.
I'm repairing just that , it's drying in the oven now.

[Mark Hammer]

Eminently sensible reply. We tend to forget about the various "normal" asymmetries inherent in speakers like the voice-coil wires, or even seams.

When it comes to big speakers with stout robust cones, the weight of glue probably amounts to nothing important.

When it comes to smaller speakers with thin light cones, the weight of glue might be important, but you make a very cogent point that the spider does much to maintain the coil/cone on axis. Plus, with a shorter distance from coil to edge/rim, it is hard to imagine any off-axis movement being caused by anything other than extreme changes in weight.

I yield...with respect.

[rockin roy]

Elmers and tissue paper works. I've used it on lots of cracked TV speakers.
The srew driver holes were put in your speakers to add fuzz. It was common in the 60's. I'd just leave it. I have a pair of JBL's from the palace and would't think of changing them. I often wonder if janice or Hendrix used them. Who made them? If they are all on one side add a few to the other side.