Unscrew the two screws at the top of both sides of the door asw ell as the screw behing the grab handle. (If think those are the only screws

) Then you can just sift the panel upwards and it will come off.
It is difficult to get to the speaker as it is behing some issulation material which you will have to try and open without tearing to et it out

Audi A3 1.8T
ex "BroSpeed" RXi