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Speaker Repair

Speaker Foam Surround Repair

This page provides a step by step guide for replacing the foam surround on your speakers

After about 15 years, the foam surround on the woofer will begin to lose its ability to function properly and will even begin to fall apart. A foam surround that is still functional will spring back when gently pressed with a finger. A bad surround will either already have holes in it or will tear easily if pressed. Speakers with bad surrounds will lose their bass response, may make buzzing noises when playing, and the cone may even wobble in the frame.

Replacing foam surrounds can be done fairly easily. The first step is to buy a foam surround replacement kit. The kits I used for this project were purchased from Newfoam out of Rochester, NY. I was very happy with the kits I purchased from Newfoam. Some kits come with the option of buying the dust caps or not. I recommend buying kits with dust caps and voice coil shims as, by my experience, you do not want to attempt a foam surround replacement project without immobilizing and aligning the voice coil as a key step. This requires removal of the dust cap, and you will want new caps to finish the job professionally. The kit supplier will have instructions for measuring your speakers to select the proper dimension foam surounds and dust caps.

I have two pair of speakers to replace the foam on in this project. The white speakers are 15 inch Techniques speakers. The black speakers are 8 inch JBL speakers.

A larger more detailed image can be seen by clicking on each of the thumbnail images

1. Remove The Speakers From The Cabinet

This is best done with the speaker on the floor with the speaker facing up. Remove the screws and lift the speaker out of the hole in the cabinet. You may need to use a putty knife to free the speaker if it sticks to the cabinet. Make sure to note how the wires are connected to the speaker. The must be connected in exactly the same way. Care must be taken to avoid damage to the speaker cone now and throughout the project, least you want to turn a refoaming project into a reconing project. Notice the large chunks of foam missing from my speakers. The Techniques speakers failed silently, I just noticed one day that the bass was gone. The JBL speakers became buzzy and distorted.

2. Tools You Will Need

  • Exacto knife
  • 1/2 inch Chisel
  • Putty Knife
  • Arlene's Tackey Glue (provided in the kit)
  • (not pictured) Six 0.01 inch thick voice coil shims (provided in the kit)

3. Remove All Old Foam

All of the old foam must be removed from the cone and the speaker frame. If your speaker has a trim ring on the outermost edge of the foam in the frame, remove it first and set it aside to be reinstalled. To remove the trim ring, use the exacto knife to separate the trim ring from the metal basket. Once the trim ring is gone, use the putty knife or the chisel to remove the foam from the metal frame. I found that the back side of the exacto blade worked well for rubbing the foam off of the speaker cone. Do not use solvants to remove the foam as they may damage the cone or prevent the glue from sticking.

Old foam removed from the frames.

The back side of the cone with all foam removed


4. Remove Dust Cap

Make sure your work area is clean. Once you remove the dust cap care must be taken to ensure that no particles fall into the exposed voice coil. Locate where the wires enter the cone beneath the dust cap. When cutting the cap take care not to damage these wires. cut an X in the face of the dust cap from edge to edge. The wires whould be under one of the resulting wedges. Peel each wedge back a litle so you can see the wires and the coil. Carefully cut along the glue line between the cap and the cone and remove each wedge. Leave the thin line of glue, it will be covered by the new cap, and removing it is not worth the potential damage to the cone.

Locating the wires

Two wedges of dust cap removed


5. Shim The Voice Coil

Placing shims into the gap between the voice coil and the center magnetic pole piece ensures proper alignment of the voice coil when attaching the new foam. Proper aligment is crucial for proper operation. A misaligned coil may rub and potentially cause the speaker to fail after some time. Use three 0.01 inch shims spaced equally around the inside circumfrence of the coil.

Voice coil without shims

Voice coil with shims in place


6. Extend The Cone, Place New Foam

The original foam on your speaker may have been glued to the top of the cone or the bottom. The foam on my speakers was glued to the bottom. If the foam needs to be glued to the bottom, with the shims in place the cone can be extended to raise the edge of the cone above the frame. This is a temporary position for the cone to make gluing the foam to the cone easier. When the time comes to glue the foam to the frame the cone will be restored to its resting position with the spider level (the orange springy disk around the outer base of the cone ). If the foam is to be glued to the top of the cone, the cone does not need to be extended to get the foam in the correct position. Place the new foam such that it is in the proper position with respect to either the top or bottom of the cone edge and the frame.


7. Glue Foam to Cone

Spread an even layer of Arlenes Tacky glue between the foam and the cone. You may find it easier to work from the back side of the speaker if the foam is glued to the back of the cone, or you may work from the front and lift the cone edge (foam on bottom) or the foam edge (foam on top). Press the foam and cone surfaces together, working continously in a circle until the glue sets enough to prevent the foam from springing away from the cone. Allow the glue to set no less than 2 hours. When dry the glue will be clear.


8. Dress The Cone To Foam Edge

Apply a thin bead of glue on the face of the speaker along the line where the foam and cone meet.


9. Glue Foam to Frame

If the cone is still extended, return the cone to its resting position. Make sure the spider is level, and that the shims are still firmly set and evenly spaced. Gently lift the edge of the foam ring and spread a thin layer of glue on the frame. Press the foam to the rung until the glue is set. Allow to set for no less that 2 hours.


10. Remove Shims, Glue On Dust Cap

Remove the shims from around the voice coil. Apply a thin bead of glue to the edge of the dust cap and place it over the voice coil. The new dust caps should be a little bigger than the originals to cover the old dust cap glue ring. Allow the glue to set for 2 hours.


11. Reattach Original Trim Ring

Apply glue to the trim ring and place it back in its original position at the edge of the speaker frame. Turn the speaker over to allow the weight of the speaker to hold the trim ring in place while the glue sets. Allow the glue to set for a minimum of 8 hours.


12. Fully Repaired Speakers

When reinstalling the speakers, be sure to observe the correct polarity of the connections.

15 inch Techniques Speakers

8 inch JBL Speaker



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Copyright Charles S. McFalls, Jr.