[NJARC] How to fix a torn speaker cone

Wed Dec 5 18:41:32 EST 2018

    I made a real train wreck of the speaker cone before I worked on it.  First, thank you to everyone who offered some really excellent tips, suggestions and experiences.  Even a PP presentation on how to fix it.  That alone sealed the deal on how I was going to approach the repair.  If it had been at all possible, I would have taken the speaker out and replaced it.  But, what to do when Emerson rivets and bolts the speaker to the chassis.  This radio just wasn't worth the time to go through all of the work for that.  
    So, here's what I considered...  Someone suggested model airplane paper ( I had vast experience with that when I was young and building model airplanes), but there are absolutely no model shops anywhere near me here in Maine.  Then another suggestion was to use "Interface Lining" (Pellon "865F Bi-stitch - Lite") that offered hope.  You've got it, once again, unobtainium here in good old Maine.  Paper towels, tissues, and toilet paper were suggested, possibly OK in a smaller fix situation, but too fragile to work with in this situation.  Yes, I really did make a mess of this speaker.  I'll cover the next speaker with a sheet of lauan and securely fasten it.  I can't believe it to be true, but in looking over my radio collection, I don't have one that it permanently attached to the chassis.
    Here's what I did...  coffee filter!  I was out shopping and looked over the thickness of coffee filters.  Not being a coffee drinker and eschewing anything remotely with a coffee flavour, I'm definitely in new territory.  This had been recommended by someone who responded to me, and of all things, a customer in the craft shop I was in looking for the Interface lining.  She said to me that a coffee filter was sometimes used as a substitute for Interface lining.  Bingo!  Coffee filters are sold in bleached white and natural.  Natural is right in the ball park for color.  Once I used the cement I'll mention below, it becomes invisible.

    The repair took me the better part of an hour once I got started.  On one of my visits to Green Brook Electronics in NJ, I picked up a bottle of Speaker Service Cement.  It's still available from MG Chemical. ( https://www.mgchemicals.com/products/adhesives/general-purpose-adhesives/speaker-service-cement-8337 )    This product is black and resembles a type of rubber cement in consistency.  Use with adequate ventilation as well.   I bought it years ago and am surprised it never hardened.  When I bought it, I was thinking that it might come in handy some day.  Just like that unusual tool we all have stored in our tool box.
     The speaker had multiple tears and punctures.  Trying to do a simple seam repair wasn't going to work.  The first thing I did was to make sure the speaker cone was securely attached to the voice coil tube and that the dust cover was securely attached.  Using the Speaker Service Cement, I put a light bead on the upper edge of the speaker voice coil tube and and reattached the speaker cone to it.  I used a small flat wedge as a prop to keep everything stationary until the cement cured.  The next step was the most time consuming, and if you are going to do this yourself, wear protective gloves.  Trying to get the adhesive off of your hands could require acetone.  

    Depending on the area being worked on, I cut a piece of the coffee filter paper to fit over the tear in the speaker.  I started with the smallest tear I could. This cement is somewhat like working with contact cement in that once you put the repair patch down, you are pretty much committed to where it's put.  To keep the mess down, I wiped the cement on the back side of the patch using a round toothpick.  There's no reason for the toothpick other than it made wiping the cement on the patch easy work.  The supplied brush(s) seemed to me to be too abrasive.  Thus the reason for the gloves.  You don't need much, but be sure you wipe some over the entire surface of the patch.  Do not put any on the speaker.  Once you have the split on the speaker cone lined up, secured as best you can for it not to move, then lay the patch on the speaker cone.  If I could have put some "Invisible Tape" on the back, that would have helped.  Where I was working didn't allow me to do that. I used round toothpicks to sort of press the patch onto the speaker cone from the center out.  This squeezes out any excess cement and helps to seal the edges.  All of this was experimentation, but it worked.    

     The rest of the speaker repair was much more tedious, but with patience, I managed to get it all back together.  I had considered other adhesives and cements such as white glue, diluted white glue, and rubber cement.  Nail polish was something I might have used on a small puncture with some tissue paper to seal it. About the only reason  I could see not to use the white glue was that it gets brittle.  It would likely hold up on smaller tears, but this wasn't anything small.  At least I had all of the cone.  The rubber cement had it's strong points, and would probably work OK.  If I hadn't had the Speaker Service Cement, the rubber cement would have been my choice.  I think that part of the bottom line for any speaker repair is to consider each situation as unique.  I had more than a simple puncture, or tear.  This was a full blown combination of all.  The other considerations are how much of a patch is needed, does it exceed the field of the cone and go into the ripple on the outer edge.  You need flexibility there.  The Speaker Service Cement has the flexibility I needed in this application.  
    At this time, I'm still working on the electronics of the radio.  I don't expect the speaker to sound as good as new, but as long as it works, that will be the success I am looking for.  It's not a high end radio (Emerson Model 550), but a good learning tool, if you need one.  Something similar could be a project for you.
Thanks for all of your input.
Joe Devonshire     

-----Original Message-----
From: Sal Brisindi via NJARC <njarc at mailman.qth.net>
To: rob.a.reifenheiser <rob.a.reifenheiser at gmail.com>; trainbee <trainbee at aol.com>
Cc: njarc <njarc at mailman.qth.net>
Sent: Wed, Dec 5, 2018 2:50 am
Subject: Re: [NJARC] How to fix a torn speaker cone

Joe,
If the paper cone is all there, I used Elmers Glue and run a bead of glue on both ends of the ripped cone and just put them together. 

Sal

-----Original Message-----
From: Rob Reifenheiser <rob.a.reifenheiser at gmail.com>
To: TrainBee <trainbee at aol.com>
Cc: Reflector <njarc at mailman.qth.net>
Sent: Sun, Dec 2, 2018 11:37 pm
Subject: Re: [NJARC] How to fix a torn speaker cone

I've had great success with a teabag and Loctite flexible adhesive (from Depot).
I've put my finger through too many.
Rob

On Sun, Dec 2, 2018, 8:58 PM TrainBee via NJARC <njarc at mailman.qth.net wrote:

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   I could use some suggestions on how to repair a torn speaker cone.  I was working on a radio that I couldn't take the speaker out of.  Of course, if it could happen to me, it will.  As I was working on the chassis, it tipped and landed right on the speaker cone.  It now has a nice big tear.
    I've heard of all sorts of repair tips from tissues, and paper towels (non treated), to coffee filter material.  I'd like to know what works best and what adhesive works best.  At least I can get to the back of the cone to keep it from collapsing inward when I work on it.

Thanks in advance for your help.Joe Devonshire______________________________________________________________
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