Sagging Voice Coils?

Yes, the talk on the net is for real. They used that dope on midranges and maybe even tweeters. Some said it also was for dampening. It always seems to stay shiny and new looking.

The talk about the voice coil rubbing happens too. I don't recall the brands, but they must of had heavy woofers. These were all vintage that I know of, but not all brands. The spider keeps the voice coil centered, but the weight of the cones on the surround, and spider will let the gap get tighter. I've felt older speaker cone movement that was tight do to this. They would scape on the one side only, that was apparently do to sag, if you carefully moved them. I rotated them before selling or trading them.

With newer materials, there doesn't seem to be any problem anymore, but who knows when they get older.

These were built in the '90s, and they knew about the sag problem then. [http://www.roger-russell.com/xl1w.htm]

This isn't a theory, it's a fact. It's not like a cable type of discussion where people have different results, without any measurements to back it up. It's just like people put their classic cars on blocks to keep the springs from sagging. The spider and surrounds on the speaker are it's suspension. And gravity does pull them down, whether their forward, or downward firing. There is evidence of it around the world, not just theory. It's not something that comes out of the minds of bored audiophiles. I imagine if you ask any one that recones vintage speakers, they will probably have seen one that has damage from the voice coil, or former rubbing, do to sag. I have seen it visually, and felt it moving the cones.

If you check the net, there are a lot of people that heard what they describe as buzzing and was told to rotate their woofers, and they had good results after doing it.

Step six in this talks about sag in older drivers. I don't think it's their imagination, or something they dreamed up.
[http://www.decware.com/newsite/refoam.htm]

Rodman, if your referring to me, the woofer cone is pulling on the spider causing the distortion in its (spider) shape. If there was no cone weight on it, I doubt the spider would sag in its lifetime. The midrange and tweeter with their light cones gives anyone an idea, the spider itself is not the problem. That's self explanatory with the woofers weight being the major cause of this problem. FWIW, there's still a problem with sagging from the weight of the cone. Some have it more than others. Larger gaps allow for more error. Also lighter cones, stiffer surrounds, and stiffer spiders along with other design factors come into play for the failure rate. Again, the problem still exists for some.

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.