Speaker's top plate disc jumped out

[Rupss]

I have two Celestion BN12-300X speakers installed in a custom-built 2x12" 4-ohm cabinet (600w).

One day during rehearsals, the top plate disc of one of the speakers suddenly shifted forward, slightly detaching the dust cap. I carefully pushed the top plate back into place (attached to the magnet), and the speaker does not seem to produce any strange noises, although I only tested it briefly as I wasn't sure if it was safe to use.
I removed the dust cap, and there is what I believe to be a voice coil former made of Kapton exposed (that optical membrane look-a-like thing), which has some small scratches on it (visible on the top of the voice coil former in the photo). I'm not experienced enough to understand if there is any serious damage.

Can the speaker still be used safely with a dust cap replacement? If so, which kind of glue do you recommend? I've read that PVA glues are better... the cone material is Kevlar-loaded paper.
Also, could you help me understand what might have caused this issue? Could it be related to a polarity problem? I was using an Ampeg SVT-VR head at the time, and its polarity switch had been activated.

Thanks to everyone who will help me!

 

[agedhorse]

You now have a permanently damaged speaker.

 

[Tj smith]

Is it the dust cap that came off? If so, u can replace them. You glue them on with super glue. I had an Ampeg svt410 that I replaced the caps on. Super easy to do.

 

[agedhorse]

Is it the dust cap that came off? If so, u can replace them. You glue them on with super glue.

No, you don’t use superglue. Where does this info come from?

It looks like the return plate came loose, the op removed the dust cap in a valiant attempt to fix it.

 

[Tj smith]

No, you don't use superglue. Where does this info come from?

It looks like the return plate came loose, the op removed the dust cap in a valiant attempt to fix it.

Relax bud, it looked like a dust cap.

 

[TheReceder]

I'd replaced the dustcap on a JBLE140, and the JBL adhesive wasn't like a superglue. It seemed to be a softer material that wouldn't be absorbed into the cone. It was similar to (but probably not) an RTV.

 

[agedhorse]

Relax bud, it looked like a dust cap.

Re-read post #1

I'd replaced the dustcap on a JBLE140, and the JBL adhesive wasn't like a superglue. It seemed to be a softer material that wouldn't be absorbed into the cone. It was similar to (but probably not) an RTV.

The factory dust cap adhesive for E-140 is a MEK solvent based glue (black) that dries very hard. This is because the dust cap actually sits directly on top of the bobbin and the ~.030" return lip fits over the bobbin OD. The reason for the very hard glue is so that the dust cap is mechanically coupled to the bobbin for the transfer of HF energy and more extended HF response. Others use a similar glue but it's not the only glue used. The other 1/2 of the glues used are a latex-PVA based, they are used for paper-paper bonding with or without a lipped dust cap that will be larger than the bobbin diameter.

There are some other specialty adhesives, especially with poly cones or plastic dust caps. Some manufacturers use a special gelled CA (a type of super-glue) that is moisture/chemical or UV cured, but this is not common.

Nobody uses RTV (fortunately).