Helped my son replace the factory rear 8" subwoofer.
The radio has had no bass to it for a while. I told him it's either the amp (behind glovebox) is bad or the sub. He bought a new sub (Planet Audio 8" dual voice coil, ~$35).
The factory sub's surround was totally disintegrated except for a small section. The new one, after wiring the voice coils in parallel with jumper wires, fit great (had to drill new mounting holes though) and sounds great.
I actually did all the work, he just held the light and handed me tools...lol