Sagging Voice Coils?

The article should be more specific. They should state something in the order that the sag could cause it to be off center. I think their main concern is to get the person doing it with no knowledge, good even clearance around the coil. If they're referring to upward firing woofers, I can't think of any companies that do this. I wasn't sure if you knew that I understand how the speakers are designed. I think we both know what is going on.

After looking at it and reading it again, they may also be concerned that the person doesn't push the former all the way down, and bottom it out especially more so, since they use shims.

Not urban legend at all! Anyone with enough years in speaker restoration will have seen this problem. I have a variation on the sag problem: A friend and I are restoring a pair of Fulton J Modular speakers. The 12" subwoofer drivers face downward, firing into a slot. 30+ years of continuous 1G force has pulled the cones downward by maybe 3/16 of an inch, even when the drivers are held facing "forward" or "upward", resulting in measurable changes to the Fs and Qts, compared to a new old stock driver. And this shift has also reduced the symmetrical Xmax. The cones are still centered properly and there is no voice coil rub. We plan to "exercise" the drivers for a few days on a table top with an amp driving them at high excursion at the free-air resonant frequency (to keep power in the voice coil low). Hopefully this will loosen the spider and pleated-cloth surround and recenter the cone at the mid-point of the excursion range. If not, then scary combinations of heat and amateur chemistry will be attempted. Any advice based on real experience would be appreciated.

Thanks, Brian

Sounds like jive to me.Dude.