This is an old thread, but I found it today looking for a solution to the degenerated left front door speaker in my daughters 2004 Liberty. The foam had separated just a little more than 3/4 of the way around the outer edge, where the foam meets the speaker frame. It was still attached to the cone all around.
I contemplated buying the foam repair rings from Ebay, but thought instead of another solution. I'm using
aquarium silicone sealant (3 oz.) to fill in the gap between the outer frame support edge and the foam edge. I worked in stages about 2" at a time and used the flat end of a zip tie to force it into the slot and smooth it out as I went. The silicone will seal the foam to the outer wall if the frame and will remain slightly pliable as the speaker vibrates.
I doubt the audio qualities will be stellar, but for the cost of some silicone I think this will repair the speaker and get us down the road so to speak. As it was, the speaker was absolutely useless due to the popping sounds it made with the loose foam. So anything is going to be better than that.
Here's a few pictures of the speaker after the silicone was applied.
I'll re-post an update tomorrow concerning sound quality.