Damaged 1969 G12M. Best way to repair?

[audiogroove]

I have a very nice (well, used to be) Feb 1969 Pre Rola Celestion T1511 G12M 25 watt 55hz speaker with Pulsonic 34 102 014 cone stamp that something fell on.

The voice coil doesn't rub and it appears in good shape aside from the multiple tears in the cone.

What is the best way to repair the tears that will keep it sounding as close as possible to it's pre damaged state?

The tears are all clean, no holes or uneven rips. Is there a specific adhesive to use? Tissue paper? Or is there something stronger available?

Any help would be greatly appreciated.

 

[BygoneTones]

ouch.

I normally use craft paper and copydex, but have never operated on anything as severe as that. If you have any spare donor cones you could try the pleximaster skin graft technique - take a layer of paper from your donor cone and glue it over the tears.

 

[GIBSON67]

I've used screen mesh and silicone glue on some severe cases but never on something that severe!
I think the main thing is to use as small an amount as possible to do the repair...every bit of extra weight
will have an effect on the efficiency and toanz.

 

[audiogroove]

ouch.

I normally use craft paper and copydex, but have never operated on anything as severe as that. If you have any spare donor cones you could try the pleximaster skin graft technique - take a layer of paper from your donor cone and glue it over the tears.

Hi Bygone,
Thanks for your response. Not sure what copydex is.

Do you apply your fix to both sides of the cone?

With your technique does it change the sound of the speaker drastically?

Seems like the pleximaster technique would have a rather large impact on the sound, having twice the thickness over abstract parts of the cone. Although if it was the same cone the ribs would line up. I wonder if he uses the same model cones as the ones he repairs?
I don't have a donor cone anyway. At least not as thin as this one.

I'm hoping to use as little as possible to repair so as to minimize the effect anything added will have on the sound.

I'd also like to minimize the visual impact of the repair.

Not asking for much am I

I was thinking some kind of adhesive or doping maybe reinforced with heavier than usual (or multiple layers of) tissue paper of some sort? Reinforced paper towel? Some type of super thin graphite composite paper? I don't even know if that exists, but seems like it might work if it did.

Maybe there is some kind of adhesive sheet that could be placed on the cone and would melt together with the paper.
Or some sort of very fine netting reinforced with the aforementioned adhesives; clear (plastic?), or extremely fine thread or cloth.

Now that I'm thinking about it I have seen a kind of reinforced netting that might work. I think it's plastic or reinforced paper. Square not round holes. It's white though
And I also remember seeing fine clear plastic mesh used in window screen.
Now that's an idea!

 

[audiogroove]

I've used screen mesh and silicone glue on some severe cases but never on something that severe!
I think the main thing is to use as small an amount as possible to do the repair...every bit of extra weight
will have an effect on the efficiency and toanz.

Hi Gibson,
Thanks for replying.
What type of screen mesh did you use? As in window screen?
And what kind of silicone glue? Does it stay pliable after drying?
How big were the repairs?
How did the repairs affect the sound of the speakers?
What models have you repaired?

This particular speaker has very thin paper, (part of why they sound so good) so I would really like to minimize any additions if possible as you said.

Please see my post above in response to Bygone Tones as to what I was thinking to possibly use.

 

[66SuperTremolo]

No disrespect but I Think that one is beyond repair. The odd tear or hole can be patched but that's extensive damage to the cone.
By the amount of built up dirt and crap on the rim of the cone obscuring the damping it looks like it was on its last legs.

There should be a bunch of videos on You Tube regarding cone repair.

 

[BygoneTones]

Id be inclined to agree and say it was toast. But it is usually worth at least having a go at a repair, before ripping the cone out altogether.

There is a thread on here somewhere started by pleximaster. He worked some magic into some very badly torn speakers. I know they were a mess beforehand because I sold them to him. I think the basic procedure is to take thin layers of paper from your donor cone, not the entire thickness of the cone. Maybe he will see this and chime in.

Best to be as minimalistic as you can. Basically the more stuff you put on the cone the more it will alter the sound.

Copydex is the basic white glue available in UK, rubber based.

 

[audiogroove]

Cool. Thanks BT. I'm pretty confident I can fix it, I just need to figure out the best materials to use. Thanks for the youtube tip 66.
I think the trick is to make the repair as strong/stronger than the cone material while still keeping the cone close to the flexibility it had beforehand.

 

[Hillcountry]

I once repaired a cone similar to that with some diluted white glue and thin strips of silk long underwear. Worked fine for a while until the coils started to rub. The tear in mine was "vertical" meaning from the coil to the edge so my repair made it look like an old Jensen seamed cone. The nature of your tear - across the cone - will make the flexing of the cone uneven. My concern is that the cone will twist as you play and damage the coil. I guess it is worth a shot fixing it though. Worst case is it doesn't work...it is already broken.

Good luck. I hate that feeling when something like this happens.

Geoff

 

[Ghostman]

Find another 12" speaker to use the cone material as patches. There's a lot of YT videos of this exact type of repair that work great.

The other option of course is to recone.

 

[audiogroove]

I once repaired a cone similar to that with some diluted white glue and thin strips of silk long underwear. Worked fine for a while until the coils started to rub. The tear in mine was "vertical" meaning from the coil to the edge so my repair made it look like an old Jensen seamed cone. The nature of your tear - across the cone - will make the flexing of the cone uneven. My concern is that the cone will twist as you play and damage the coil. I guess it is worth a shot fixing it though. Worst case is it doesn't work...it is already broken.

Good luck. I hate that feeling when something like this happens.

Geoff

Thanks Geoff,
I appreciate the suggestions.
Yeah , Im sure you know how I felt when I saw it.

 

[audiogroove]

Find another 12" speaker to use the cone material as patches. There's a lot of YT videos of this exact type of repair that work great.

The other option of course is to recone.

Thanks for the suggestion Ghostman. Only way I'll recone it without trying to fix it first is if I can find an original cone

 

[Woods]

Re-cone her and roll on, no ghetto fixes please.

 

[Georgiatec]

FWIW I have a similar speaker from April '69 that I had to have re-coned and it now sounds fantastic. Definitely worth doing. I used the Heritage kit from Lean Business here in the UK. Not cheap, but great sounding.

 

[66SuperTremolo]

https://youtu.be/hSbTbuZ-55Q

Gerald Weber - Kendrick Amps

 

[soundboy57]

It's toast. It will never sound the same, and IMHO worse than a correct recone, especially in the mids and during breakup.

Here is a great comparison vid of a repaired vs original Pulsonic greenback. The speaker wasn't as bad as yours, and to me, it sounds nothing like the original....let alone any version of a good greenback.

As for getting a new cone, I like the reissue standard greenback tone better than the Heritage series, but that's just me.


https://www.youtube.com/watch?v=aIHDKISSYAQ

 

[audiogroove]

Thanks for the suggestions guys. The youtube links were helpful and I found a couple really good techniques to try. Here is one of the links:

https://www.youtube.com/watch?v=jW7xuJ2gHOY

 

[66SuperTremolo]

It's toast. It will never sound the same, and IMHO worse than a correct recone, especially in the mids and during breakup.

Here is a great comparison vid of a repaired vs original Pulsonic greenback. The speaker wasn't as bad as yours, and to me, it sounds nothing like the original....let alone any version of a good greenback.

As for getting a new cone, I like the reissue standard greenback tone better than the Heritage series, but that's just me.


https://www.youtube.com/watch?v=aIHDKISSYAQ

Yep, big difference quite audible. George Metropolis has a video comparing various speakers to his original 67 greenback. To my ears the reissue standard G12M straight out of the box came Very close in tone to the original.

 

[keennay]

Hmm, wait a minute. The repaired speaker in Johan's clip sounded better than the original (undamaged) one... at least to me.

Audiogroove, did your speaker come from a 4x12? If so, by that logic it makes sense to slash the other 3 & recone.

 

[soundboy57]

Hmm, wait a minute. The repaired speaker in Johan's clip sounded better than the original (undamaged) one... at least to me.

Audiogroove, did your speaker come from a 4x12? If so, by that logic it makes sense to slash the other 3 & recone.

It does sound brighter on a laptop...but through good full range speakers (JBL and Dynaudio studio monitors) it sounds terrible, IMHO.