Cleaning Large Advent speaker grill cloth

When I get to such a speaker, I remove the cloth from the frame, via staples or the glue they are held by and wash it in warm water and dish soap. Lots of dish soap. Then go on to more aggressive cleaning solutions, if necessary.

Reglue is by a warm iron, and the thickest pant hemming glue rolls one can find at the local fabric shop. This is exactly what the original manufacturers use.

Start in the middle of each length and work toward the corners. That's how you stretch a painter's canvas for stapling and the same way you stretch and mount a grille cloth. Move evenly out from the center, on both sides of the given center of each side. Always doing each side evenly with respect to one another (all four simultaneously).

Watch web videos for paint canvas stretching, to see how it is done.

Just a thought here but I honestly don't know the outcome?
What if you took the speaker cloth on the frame to a drycleaners and asked them for a professional oppinion?

you can find plenty of grill clothes clean and brand nu at partsexpress.com

might be the best way to go, unless you are trying to somehow preserve exact originality.