Hey guys i would like to know if someone has changed his factory sub speaker in the original case and what size is it?

Iv never done it but im sure its easy hardest bit will be sorting the wireing out

i think its 8 inches but im not sure

i dont think it would be worth the effort. The standard sub will probably be more sensitive than a cheap aftermarket sub so the amp just would be no good. and if you plan to put anything other than a cheap sub in you will be wasting good money.
Also the speaker will be very small in comparison to other 8" subs so geting it to fit would be a task.

yeah i know the effort does not worth it but i don't have the space for other one i need the stupid small trunk

I would recommend a decent set of components up front then.

Hertz DSK 165 a got these but still not good missing the bass and i'm :bang: what to do i think its 13cm sub speaker

What amp are you using. Seriously putting a different speaker in the standard sub box is pointless. I think even a half decent set of 6x9's in a wooden parcel shelf would be better. Have you ever thought od something like the Genesis 6x9 subs.
Or something like this built into a box which you could make part of an MDF Shelf.