2006 Pathfinder Rear Speakers

Hello Friends.. Does anyone know how to get to the rear subwoofer (in the far back, not the rear door) in a 2006 Pathfinder? My speaker is blown and I need to replace it, however I cannot get the cover off. The cover looks like it is not clamped or screwed on. I have tried to stick a spackling knife into between the cover and the panel, which I am able to but the cover just will not come off.

Any help would be much appreciated. I cant stand hearing the blown woofer anymore and really do not want to spend the money to take it somewhere.

Please help.