Intro: How to Refoam Your Woofer
During the seventies and eighties, either planned obsolescense, poor engineering, or short-sightedness caused speaker manufacterers to use a type of rubber surround for drivers that deteriorates with age. Perhaps you have a pair of speakers that show the classic grainy, dirty looking speaker surrounds or maybe even have holes in them already. I got a pair of old Advent Heritage speakers from a guy for free because the surrounds were shot. The previous owner tried using silicone caulk to stave off the inevitable to no avail.
For about ten bucks a driver, you can replace the foam surrounds if you have some patience and determination.
There was a time when the quality of a manufacturer's equipment was what determined their success, rather than the amount of money they spend on advertising. While those days are past, much of this aging Hi fi equipment can be found on craiglist or freecycle for a song. At best, they are ready to go with a little dusting. Sometimes, however, the drivers need to be refoamed. Would you like to get started?
Step 1: Stuff to Get:
Obviously you will need an old pair of speakers. The foam surround kits are not inexpensive so make sure you are getting a decent pair of speakers to begin with. Also the paper cones should move freely and they should still make sound when played. All the drivers should play. If they have been energized a lot with the surrounds damaged, the voice coil could be abraided away, shorted out, etc. Those should be avoided because I don't think that's an easy fix. Today we are working on a pair of Advent Heritage speakers. They are not the classic Advents and were produced after Jensen bought the company and ruined it. However these speakers, despite, their shortfalls, sound really good to my ears. The cabinets are pecan and clean up really well.
Razor blade, hobby knife, or scalpel
Stiff brush or toothbrush
Can of air
Speaker refoam kit http://stores.ebay.com/GeoAli-Vintage-Stereo-and-More
The kit I purchased included the glue, paint brushes, shims, speaker edges, and instructions.
Wood care products of choice (I'm using Howard's Restore a Finish and orange oil cleaner)
Clamps, c-clamps or the like if you have beauty rings to clamp into place.
Hair dryer or heat gun if your speakers have vanity rings around the basket ring.
Step 2: Disassembly
Take all the drivers out and make sure the leads are all in place. Don't confuse where they go or you will have the crossovers driving the wrong driver when you put them back together.
While the drivers are out, give the cabinets a good cleaning. Howard's Restore-a-Finish is pretty good stuff. It doesn't have much color to it but it does have some. It can really make scratches less noticeable.
I won't go into messing with the crossovers or any of that kind of stuff for this instructable. However some people would go through those systems and either upgrade the capacitors or at least test them out. I make sure they play before I take them apart and when I put them together I play them again and listen critically as possible. Make sure all the drivers work. I don't think anyone can hear the difference between one capacitator and another (of the same value.) Like $500 speaker wire, it's voodoo to sell to people: would you like me to fill your tires with scented air, sir?
Step 3: Clean the Cabinets
Most speakers are made with mdf. On top of the mdf you may find veneer if you are lucky. If you find sticky paper, you probably shouldn't bother doing this procedure at all anyway.
I clean them up nicely; maybe use a brown maker or stain marker to touch up the scratches. Use a finish restorer or just furniture polish off the shelf. You'd be surprised how nice they can look with just a good scrubbing with a rag and some off the shelf lemon or orange oil furniture spray.
I took the cloth speaker covers out to the back yard and sprayed them with 409 and the hose to get twenty years worth of nicotine out of them. The color fast synthetic material looked great when I was done. Use your head if your panels are not synthetic, woolite and a damp rag may be better. However, the synthetics were cheaper so that's mostly what I've found.
Step 4: Remove the Old Foam Surrounds
To remove the old gaskets, just use your finger to pick off as much as you can.
Then use your toothbrush or stiff nylon brush to remove as much of the old material as possible. Don't bother trying to remove the glue. Also if your drivers are even half way decent, they will be really tough. Don't worry about ruining them. However try not to damage the voice coil by dragging the cone up and down in the basket while you are doing all this.
In the picture below you can plainly see that there is a plastic beauty ring covering the part of the gasket or speaker edging foam where it attaches to the basket. This has to be removed. I couldn't figure it out at first but the supplier whom I purchased them from emailed me back the same day to explain the problem and give me a solution to it. I used a hair dryer to soften the glue then gently pried the rings off with screwdrivers. Worked like a charm.
Step 5: Remove Beauty Ring If You Have One
My speakers gave me a bit of trouble getting the ring off the basket but after some hair dryer action and gentle prying,everything came along.
Step 6: Cut Off Dust Caps
The dust caps need to be cut off with a razor, an Exacto knife or the like. Be as neat as you can because this is the one area where you can mess up. If your caps are dented up, now is a good time to make them nice again. Either take them all the way off or leave them with a little thread or hinge to fold them back. The hinge works great but makes un-denting them harder.
To un-dent, use a form and a hair dryer. Soften them up with a dryer and put them over a form like a tennis ball and put them into shape. If they won't hold their shape you can use some spray starch for clothing on them.
Try not to get stuff under the dust cap. Blow them out with a can of air or compressor.
Step 7: Shim Up the Voice Coil
Your kit came with some strips of paper to hold the voice coil in place. This allows the voice coil to be locked into place while you are gluing the surrounds on. Do not forget this step or you will glue the surrounds on with uneven tension. This will cause the voice coil to abrade away against the magnet. Eventually it will short and your speaker will be dead. Don't kill speakers. That's bad.
Keep putting the shims around and around like a the petals of a flower until you can't get any more to go in. They go in the crack between the voice coil and the magnet plinth.
Step 8: Glue the Foam Edge in Place
Using the clear drying glue that came with the kit, glue the foam edge into place. The instructions say to do the inside first, let it dry, then do the outside. However, since I had the beauty rings to act as full circle clamps, I did both parts at once.
The kit comes with paint brushes, use them. Even though the glue dries clear, neatness counts.
Doing the inside and outside separately makes it half as likely that you will put unequal tension on the surround. This could ruin the driver. Take your time. This is really the only part of the speaker that goes bad, they will be good for another 20 years if you do them right.
Put a layer of glue on both sides of the joint. Pinch everything together with your fingers going around and around, removing excess glue with a damp rag as you go. Once you are sure you have everything touching and there is no unequal tension and no gaps, you are done.
I used the beauty rings and clamps. If you don't have the rings, then you don't need the clamps.
Step 9: Clamp on the Beauty Rings
I used the beauty rings to clamp the outside edges down. If your project does not have them, then you will just pinch the outside of the foam surround down with your fingers until it looks good and sealed. Wipe away excess glue with a damp towel.
Step 10: Allow to Dry
The glue dries overnight. Use this time to finish cleaning up your cabinets. You may want to replace the connecting wire with something more substantial. Make sure the caps in the crossovers aren't leaking. Deoxit your connections or clean with a wire brush and apply some dielectric grease (also called 'tune up grease'). Play with the dogs. Get ready to rock.
Step 11: Glue the Dust Caps Back On
Nothing like a job well done. Waiting over night for the glue to dry sucks. What can you do?
Gaze upon the glory of your handiwork. Bask in the knowledge that you will soon have your face melted.
Remove the shims.
The speaker cones should move smoothly in and out. There should be no friction. When you push them down, they should pop back up again. When you use your fingers from behind to push the driver out to its fullest excursion, it should pop back to the center again.
Put your speakers back on the bench where they won't be disturbed. Apply glue to both the dust caps and the speaker cones where you cut them off. If you left a flap, they will just fold right over. Now is the last time to make sure there is no dust or debris under the caps.
After applying glue to both sides and flipping the caps over, put a small medicine cup upside down on each cap to hold them place. Place another cup on top of that one with some screws or whatever in it. This will hold the dust cap in place while it drys. Make sure it's lined up well. The dust cap does nothing for the sound but can be an eyesore if it's messed up.
Step 12: Reassemble Your Cabinets
You will have to wait another night for the glue on the caps to dry. Then you should be ready to reassemble your cabinets.
Put a few drops of superglue into the screw holes where the drivers mount to the cabinets. MDF is good for one assembly (at best.) After that...meh. These Advents have Pecan hardwood faces. They wanna rock.
Make sure you put all the wires back in correct phase and on the correct drivers.
I hope you found this instructable useful. If so please rate it and comment.
No go and rock out!