Use a sharp knife and cut a cross through the weather shield.
Remove the 4 Torx screws and pull the speaker out.
Disconnect the wiring connection on the back of the speaker.
Get some replacement speakers the same size. You should find the originals are 6.5 inches.
You are limited by the depth of the speaker.
The depth of the original is 58mm from the mounting face to the back of the magnet.
The standard speaker clears the window by about
5mm so don't go over 60mm with your replacement speakers.
Fit the new speakers in place. The original connection will not fit the new speakers so you will have to cut the connector off and either solder them to the speaker connections, attach some spade connections or splice the old wires into the wires that come with the new speakers.
Reseal the weather seal using fabric tape like duct tape.