I have some polk speakers in my car that have a center like you describe. I used my hot glue gun with 3m yellow glue stick and it seems fine since I fixed it 2 years ago.
This is interesting since most hot glue materials are meant for porous surfaces. Rarely would it stick to a plastic especially PP.
I would have to see more info on their yellow stick composition.
My sub surround came delaminated from the main driver and I repaired it today using Lepage contact cement. With contact cement only a vey thin layer is required on each surface , I guess I will find out soon enough.
Material types are the key here. It is likely the surround is a rubber based material; very different from PP. I can see contact cement used in this instance for bonding these two materials.
Drivers are designed to be a rigid as possible while remaining light weight. I would think there is less flex at the middle than at the outmost portion of the driver.
This was also my thinking and why a cyanoacrylate might work. Question is, for how long?
I don't want to repair again, not even in 10 years. There is another part to this story about a "t-nut" and the driver screws that can complicate things in regards to removing the driver for repair, without wanting another repair.
