When the foam around a woofer speaker ages, it will crack and break off. The result is that the interior cone and voice coil may have shifted out of place. So when you replace the foam, you actually need to make sure that the interior of the speaker is still intact as well. You will need to purchase a foam repair kit. Most of them include the foam ring, cardboard shims and adhesive, but if not you will need to purchase the additional materials.
- Skill level:
Things you need
- Phillips or flat head screwdriver, or small wrench
- Speaker foam repair kit
- Razor knife (scalpel)
- Wood chisel or small putty knife
- Thin cardboard shims
- Speaker foam adhesive (poly-acrylic clear-drying glue)
Unplug and disconnect the speaker. Remove the speaker cone from the speaker housing. You will probably need to use a screwdriver or small wrench to open the speaker housing.
Remove the old foam with your fingers, with the help of the razor knife if needed. Separate the gasket from the steel frame by sliding the razor knife under the lip and running it around the circumference. This may take several attempts. Remove and set aside the gasket.
Clean the steel frame by scraping it with the wood chisel or putty knife. Continue scraping until the surface is smooth and even. Carefully scrape foam residue from the cone's outer edge as well. Your goal is to prepare these surfaces for the new adhesive.
Cut open the dust cover, the smaller black circle in the centre of the speaker. Use your razor knife to cut almost all the way around the circumference, leaving a small amount of the dust cover intact. Flip it open and tape the flap to the cone to hold it in place.
Examine the voice coil. The inner metal pole and the voice coal bobbin should not touch. Use three to four cardboard shims to hold the voice coil tightly in place. Make sure that the "spider," the disk under the cone, is flat when you place the shims. Test to see if the cone still moves up and down easily. If it does, you need thicker or stronger shims. Make sure that the shims are short enough that they will not block the dust cover when it is replaced.
Run a bead of speaker glue around the rim of the new foam ring where it attaches to the cone and also along the cone's rim. Use your finger to spread the glue evenly. Place the new foam ring in place and press it in place firmly around the ring. Don't attempt to force the ring to fit the steel rim perfectly. Continue to press it down firmly around the ring to help it adhere.
Allow the adhesive to thoroughly dry.
Run a bead of speaker glue around the underside of the gasket. Press it in place over the foam. To help it adhere, place a heavy board atop the speaker or turn it facedown on the table.
Allow the adhesive to fully dry.
Remove the cardboard shims. The voice coil should not touch anything as you move the cone up and down. If it does, you need to start over.
Run a small bead of glue around the underside edge of the dust cover. Remove the piece of tape and press the dust cover into place.
Allow the adhesive to dry.
Run a "finishing" bead of glue around the edge of the cone where it meets the foam and around the dust cover where it meets the cone. This will strengthen and seal the bonds. Carefully smooth out the glue with your finger so it will dry evenly.
Tips and warnings
- If you have a lazy susan or a turntable, place the speaker on it and slowly turn it as you apply the glue. This will help you keep a steady, even application of the adhesive.
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