Protecting vintage subwoofer cones......need advice from the experts! - diyAudio
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Old 20th January 2011, 02:27 PM   #1
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Default Protecting vintage subwoofer cones......need advice from the experts!

I am wanting to find a way to protect several vintage, paper cone, subwoofers and speakers that I own and was wondering if anyone had any experience with a specific product.

I am currently restoring several pairs of M&M Subwoofers from the mid-late 80's. These subs are new or as new but the foam surrounds have become brittle and a pair or two were in display cases and the cones were dusty and needed cleaning. Now that I am nearing completion on the restoration of the first set I am looking for a means of protecting the paper cones in the coming years. I am actually going to be installing one pair in a complete old school installation. I have thought about trying a spray silicone sealant like one would use on suede cloathing or shoes. I know there could be some minor change in sonics due to the added material on the cone but I am wondering if this would be noticable if used sparingly. I am not trying to greate a glossy finish or anything like that, just to add some protection to speakers that are 15-20 years old.

Your thoughts and advice greatly appreciated?
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Old 20th January 2011, 03:44 PM   #2
hjf is offline hjf  Argentina
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Technically, if you alter the foam, you will be modifying the driver's properties, particularly Qms (mechanical Q).

Then again, if the foam has become brittle, the driver's Qms is already modified.

If you use the sealant "sparingly" you won't be sealing anything. Pretty useless. I wouldn't worry about the paper in the cones anyway. It's the foam you should be worrying about.

Maybe you can get them re-coned? I did that once to a set of speakers I had. They only changed the foam and they looked as good as new.
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Old 20th January 2011, 03:53 PM   #3
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Thank you for the response. The surround on this pair of subs was beyond repair and I am currently replacing the surrounds on two different sets of woofers. Ideally I am wanting to do something (or nothing if that is the recommendation) to the paper cones before I glue on the new surrounds. I had looked at some polymer product said to restore a "Glossy" look to the sub while protecting it from sun and moisture, but these particular subs never had a "Glossy" look so adding anything that would change the appearance would, at least I feel, change the sound of the sub. So that is why I thought about the spray type silicone protectant. And thought it might be light enough to offer some protection without dramatically changing the qualities of the speaker.
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Old 20th January 2011, 05:01 PM   #4
badman is offline badman  United States
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Just refoam them. Lots of places sell foam kits and it's not that hard to do.

Repairing Damaged Speakers / Drivers Article By Jeff Poth
"The dawn of Bose created the "Man Cave" and reduced testoterone levels worldwide by 18.5 per cent" Peteleoni
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Old 21st January 2011, 08:20 PM   #5
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By my long experience in speaker repairing, on this way, if you are something careful you can get even better results than with re-coning speakers. If your surrounds are failed, that is other story.

So, you should to treat your paper cones with a very diluted, colorless nitrocellulose lacquer:

- First clean your cones on booth sides with dry softer brush from dust.

- Find Toluol (neoprene glue remover), and treat with him where dust cap is glued, wait 5 -6 min. repeat all 2 - 3 times, than CAREFULLY remove dust cap from cone (if you need, with some not too sharp knife).

- DILUTE nitrocellulose lack to be almost (not completely !!) like water.

- Than with such lack, treat carefully and uniformly full space of cones, also dust caps once time, at least on front side (for fat paper cones, you should treat also on back side). Don't touch surround with lack! If maybe your cones have shine glaze on front side, treat only back side something more.

- Left speakers to dry with face down, to sit only on metal edges (not on surround) for at least 24 hours on temperature something above than in normal room.

- Glue dust cap back with some universal neoprene adhesive (put something more adhesive on dust cap edges, and carefully push on place). Wait to dry.

Thats the way if you want to keep your vintage woofers with paper membranes like they was. On this way you will get practically new membrane, really stiff, but practically same weight and without characteristic change.
I mentioned to you that is possible to make better than original in case if you not dilute lack so much for better stiffness, but you should be careful if you don't want to change weight of cones, than speakers characteristics too much. If you will change, you need to change something also in their boxes where they was. For better stiffness, I would just to change complete cone with Al cone, or some advanced stiff cone system. But if you don't want, do exactly like I wrote above!


P.S. Don't use other kind of lack, and if you need to change surrounds, tell me!
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Old 21st January 2011, 09:30 PM   #6
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Originally Posted by hjf View Post
Technically, if you alter the foam, you will be modifying the driver's properties, particularly Qms (mechanical Q).
Yeah, but the Qm of a driver with a foam surround is usually so high that it should make little difference to Qts if you replace the foam surround with another similar foam surround. I wouldn't worry to much about it.
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