I’m just trying to help. Look at the attached picture.
The front face, on which the speaker is resting in this pic, is bigger than the hole through which the speaker sounds, so either the front comes off, or the back comes off. I do know that you can’t remove the speaker by working from below.
I have said that it might be the case that this chassis is liftable out from the back. You have tried to remove the front with no success. You have not commented on how it went when you tried to remove the back. I’m suggesting that you try that.