This is the third attempt refoaming the subwoofer of my 2002 LX470. The prior two attempts resulted in a metallic rattling sound from the cone during operation. I believe this failure is caused by a lack of concentricity of the voice coil with respect to the magnet.
In my case, there was no scraping during manual inspection. I pressed on the cone, even applying side loads to try to get the coil to rub, but nothing happened. This result is “technically” what you would want, but I still had that rattle. I decided to remove the dust cap for a better look.
Goof Off is very useful at softening the glue during this entire project. This particular product is advertised as a super glue (cyanoacrylate) type remover, but I reviewed the MSDS here to find that it is primarily acetone. Perfect! Acetone will soften the glue but not soak/saturate the sensitive materials like a solvent in solution with water.
I put some drops of acetone around the dust cap glue and gently cut through with a craft knife. Eventually the glue gave way and I could pry off the cap.
Immediately I noticed an eccentricity between the cone and magnet. I think there should be equal space all the way around, but in this case there is clearly a very narrow gap at the 1:30 clock position. Though the coil did not scrape against the magnet during inspection, I could imagine that in use, the magnetic field or sound vibrations could cause clattering at this spot.
I set about re-foaming the subwoofer. Many thanks to the pioneering efforts detailed in this post. Many thanks to Simple Speakers for being a quality foam supplier.
Having tried this process twice before with no luck, I decided to make a tool to control spacing between the magnet and coil. Makeshift, yes, but very effective. I simply found a piece of paperboard in the recycling that had just the right thickness to slide in between the magnet and coil. Then I cut a rectangle that could be curled into a cylinder. I inserted the cylinder down into the coil until it bottomed out. This would ensure that the spacing would be correct along the entire axis of the coil, not just at the visible end.
My theory was that with the tool in place, I could glue the new foam to the cone and speaker frame without causing any misalignment. This technique did actually work. I verified good, even space between the coil and magnet before putting on the dust cap.
Unfortunately, the subwoofer did not perform. It continued to clatter at every volume and equalizer setting. My hypothesis is that the spider is just worn out, loose. Without a strong enough spider, I can see how the voice coil could get out of alignment and clatter.
At this point I turned to sourcing a used subwoofer from a 2006 LX470. The relevant part numbers are 86150-0W010 and 6646-AB. For the replacement subwoofer, everything matches except the five digits before the “F0012”. Despite that small difference, everything seems to work great. I am very happy to have full bass again!
Allie
Pretty damn cool.
Integrating Carbon
Thank you! 🙂