Advent Speaker Refoaming Tips

As a proud owner of two original Large Advent loudspeakers [picture], I have been faced with the inevitable problem of replacing the foam surrounds on the woofers. Though these are some of the best speakers ever manufactured, the woofers do suffer from foam rot, and generally need to be refoamed.

While there is no shortage of places that will perform the service, I nevertheless chose to do it myself. It seemed not only faster and cheaper, but also more fun. For the most part, that turned out to be true. However, there were also a few pitfalls that could have easily been avoided.

These particular woofers present a few challenges in terms of refoaming. Their construction is quite unusual. Though the woofer uses a 12" basket, the cone is only 9" wide, and the gap is bridged with a masonite ring. The foam surround is inverted (it bends inward), and is glued to the back of the masonite. This makes replacing the foam surround somewhat more difficult relative to standard speakers.

I used a kit from Simply Speakers. They have very reasonable prices and sell a high-quality product. Some pictures: new foam surround, glue

Here are some tips which make refoaming much easier:

Preparation

• Remove as much old foam from the cone as possible using a sharp knife, being particularly careful not to cut into the cone material.
• Use an acetone-soaked rag to clean the old foam, glue, and other gunk from the cone circumference. Cigarette lighter fluid can also be used (it works best if small amounts are squirted right onto the cone edge). I have not had much luck with isopropyl alcohol.
• An acetone-soaked rag in combination with a sharp utility knife is good for removing the old foam and glue from the back of the masonite. Simply stick the rag into the space between the cone and the masonite, and run it along the old foam. Once the acetone softens it, use the utility knife to dislodge the stuff (stick it in from the front side of the speaker, with the blade parallel to the masonite). Repeat until the back side is reasonably clean and smooth.

Gluing the new surround

• I do not suggest gluing the surround to the outer edge of the masonite. While this is undoubtedly easier, it tends to restrict cone excursion and changes its resting position. Both of these changes are likely to degrade the sound quality.
• A small, flat brush (the kind used by artists) is very good for applying glue. I do not recommend squeezing glue from the bottle directly onto the surround, since it's hard to apply evenly. Instead, squeeze the glue onto the brush and apply a generous layer of glue onto the foam.
• First, apply glue to the inner edge of the new surround (on the side that goes against the cone). Do NOT apply glue to the cone itself. Next, insert the new surround into place, center it on the cone, and run your finger along the edge for a few minutes to ensure it is evenly glued.
• Now comes the trickiest part. Using the brush, apply glue to the outer edge of the foam surround (the one that goes against the masonite). Make sure the glue is spread on the entire outer edge. Visually center the surround relative to the masonite, and press the surround to the masonite at a few points (stick your fingers through the openings in the basket; be careful, since the edges are sharp). Make sure the cone is centered by pressing on the it at various points along the circumference and listening for scraping. Use just one finger to press on the cone; if scraping occurs, re-center the surround. Once the cone is centered, run your finger along the entire outer edge of the foam and press it to the masonite. Do this several times. Wrapping a rag around your hand helps prevent cuts. Again, check for coil scraping.
• You are practically done. Do not re-install the woofer until the glue is dry. I suggest at least 10 hours to be on the safe side. Also, ensure that everything is sealed when re-installing the woofer. Even a small air leak will significantly degrade the sound. There should be some putty or possibly a gasket around the woofer opening.
• Picture of repaired woofer.