Inverted foam surround on Wharfedale 2075A woofer

Most woofers are equipped with a foam or rubber surround that is mounted 'convex'. That is, the curvature of the edge points outwards. There are also woofers with an inverted (concave) edge. These surrounds are generally more difficult to replace than surrounds that are 'convex' mounted. In this lemma we explain how these 'inverted' mounted surrounds can be replaced.

In this case we replace the foam surround of the Wharfedale 2075A woofer, the 2074B woofer from Wharfedale uses the same surround. This manual is therefore also valid for the 2074B woofer. These woofers are used, among others, in the Valdus series.

Wharfedale 2075A woofer

First, the woofer must be removed from the speaker cabinet. Unscrew the woofer from the cabinet and take a picture of the connected wires. The wires must be reconnected properly after the repair. Mounting 'inverted' is a tricky job that does not work well when the woofer is still in the cabinet.

We found the woofer in the condition shown in the photo below. The foam surround has largely disappeared, but a partt of the surround is still visible. The photo also shows two tools that can be used for cleaning the woofer, a wood chisel and a (cloth)peg.

Wharfedale 2075A woofer with a broken inverted foam surround

For this repair we used the following tools:
Stuff used during the repair of a Wharfedale 2075A woofer

Before the new foam surround can be glued to the Wharfedale woofer, the old foam surround must be removed. We first remove the old foam surround from the woofer cone, then from the frame.

To clean the cone, we place the woofer upside down, with the magnet facing up. With a cotton swab dipped in pure alcohol, we carefully remove the old foam edge from the back of the cone.

Clean the back of the speaker cone before installing a new foam surround

Cleaning the woofer frame is easier. More force can be applied here. Clean the frame as much as possible. The old foam surround can be removed with a wood chisel, peg, and cotton swab with alcohol. Finally the frame is clean:

The woofer frame has been cleaned before gluing a new foam surround

During cleaning, the paint of the woofer frame may become scratched. That doesn't matter. It makes bonding of the glue later in the process even easier.

Now take the foam surround and place it upside down, with the bulge facing down. Now carefully slide the foam surround under the cone of the woofer:

The foam surround is placed behind the woofer's cone

When the foam surround is completely under the woofer cone, slide it into place with the bulge down. The roll (inverted) of the foam surround must fit nicely with the cone. We use this specially developed surround for the repair.

The 'inverted roll' of the foam surround must fit well with the edge of the woofer cone

Make sure that the foam surround fits nicely around the speaker cone:

The foam surround must fit nicely against the woofer cone

When the foam surround is in place, it can be glued to the cone. Because the 'lip' of the foam surround is behind the cone, we use a syringe to apply the glue.

Use a syringe to apply the glue behind the cone

It is also possible to place the woofer upside down and apply the glue from the back with the syringe. Most 'beginners' choose this method because you can better see the repair. Make sure that the foam surround does not shift!

Use a syringe to apply the glue behind the cone

With a wooden spatula, we carefully press the adhesive edge of the foam surround onto the edge of the cone for better adhesion:

Gently press the edge of the foam surround onto the cone for better adhesion

Now let the glue dry. The glue dries fairly quickly (especially on the paper cone), but we recommend putting the woofer away for at least 12 hours. The foam surround can then be glued to the frame.

Step 2: Glue to the frame.

This Wharfedale woofer has screw holes over which the foam surround partly falls. It is recommended to slightly 'cut' the foam surround at the screw holes. It prevents the foam surround from being damaged when tightening the screws.

Cut away the foam surround covering the screw holes of the woofer

The foam surround is now glued to the cone, the glue has dried, and the screw holes have been made 'free' so the screws won't damage the surround.:

Make sure that the foam surround is trimmed at the screw holes

Now apply the glue between the woofer frame and the foam surround. Again, this is easiest with a 'syringe'. Another way is to lift the foam edge slightly and apply the glue to the frame with a brush.

Apply glue between the woofer frame and the foam surround

Make sure that the glue is well distributed over the entire surface. We 'spread' the glue by spreading it all around with a wooden spatula over the glue surface:

Spread the adhesive over the entire surface to be glued

Now test whether the coil of the woofer 'runs freely' in all directions by gently pressing the woofer.

Test that the woofer coil is centered

Clips are placed all around and the woofer is tested until the coil runs freely in all directions.

Clips are placed all around and the woofer is tested until the coil runs freely in all cases.

Here is an extensive manual for centering with pegs. You can also opt for 'shimming' to center the woofer. This method is 100% reliable but more difficult to perform.
When the foam surround is glued to the frame, let the glue dry again. Again use the 12 hour period. After this period, the woofer can be placed back in the cabinet. Make sure the wires are connected correctly.

© Good Hifi VOF