Z3 Subwoofer Rattle Fix

The first problem I had that couldn’t be fixed by the dealer simply replacing a part was the ever so common subwoofer rattle. In my case, not only did the grill rattle with even the slightest bass, but the subwoofer compartment top also vibrated with increased bass. The dealer was going to order a completely new subwoofer box. Having read on various boards of similar problems, I knew it wasn’t the box itself, but the housing.

The service rep and I decided to take a look at the subwoofer compartment to determine if we could track down the source of rattle(s).

After pulling the lid off (which is not easy because the back locking tabs are not easily removed without bending or breaking the slots for the tabs) we didn’tt notice anything. So I fired up my favorite Alice in Chains CD (unplugged) as I knew a number of the tracks of this CD would cause the whole inside to rattle along with the subwoofer compartment.

After sticking our ears nearly against every potential source of the rattle noise and repeating a rattle producing track over and over again, we isolated our first rattle.

 

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The rear vertical piece has a lip that was nearly in direct contact with a speed screw holding the subwoofer box assembly in place. The back piece is very thin plastic - and with the cover off, the bass caused this piece to vibrate tremendously. To fix this rattle, the service rep split a piece of wire insulation and slipped it over the lip between the speed screw as a sort of shim. After we verified that this fixed the rattle, he applied a spot of glue to ensure the fix stayed.
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One of the things I noticed when we found this rattle was the obvious marking of the plastic from where it was vibrating against the metal of the speed screw. With this little bit of info, I started looking around for other similar signs while the service rep inspected the subwoofer box itself. The first part I inspected was the top cover. I immediately spotted the telltale markings on either side of the screws.
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Having found the vibration wear, I then looked to spot where it was vibrating against. After inspecting the area below where the cover sits, I found the corresponding rattle points. This bracket is used to hold the retaining plugs of the lid. The screws fit through the wider holes outside of the retaining plug holes. The smaller hole was apparently designed to hold a screw that fits into the cover, but no screw is used (I may add one to try to close the gap between the lid and enclosure front).
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One thing I noticed is that the bracket is badly malformed. Initially the service rep wanted to remove it and try to straighten it and grind out the larger holes to eliminate the points of contact with the lid. I suggested that we simply put some foam in place to cushion the contact point. The rep could find only some rather thick pieces of foam and some Velcro. The thick foam was too thick to use without increasing the gap between the lip and the enclosure front. Taking the Velcro, I separated the fabric piece from the hoop side, then cut a piece of the fabric side to fit around the screws and cover the contact points. After inspecting the area under the lid for any other contact point and satisfied that there were no others, we refit the lid. Once again we fired up Alice in Chains and found that these two fixes took care of the rattles under the lid.
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Next we concentrated on the subwoofer grill. Once again looking for the telltale contact wear points, we found two around the enclosure front where the grill fits. After inspecting the grill itself, I found that the contact point was the little support tabs around the grill cover.
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To cushion the support points, we simply cut little pieces of the same Velcro fabric and placed them over the wear points of the enclosure front and replaced the grill.

 

After replacing the grill, we again fired up Alice in Chains and cranked it to distortion with out a single rattle. Now thoroughly tired of the Alice in Chains CD, I drove off, top down, with Aerosmith “Back in the Saddle” cranked…and no more subwoofer rattles.