sorry for reviving this old post.
I recently had the same question/problem and couldn't find any information on how to remove the inner doorpanels
on a series 3 Doblo anywhere, so I decided to bite the bullet and make this write-up for anyone needing to do this in the future.
To access the front speakers, you will have to remove the complete inner doorpanels.
The standard speaker is pop-rivited to the door and you will need enough access to be able to drill out the rivets
(and drill new holes for the new speakers.)
Although it appears there is a seperate panel/grill in front of the speaker, DON'T try to remove this section !
It's not a detachable part and it will break when you try to remove it !
Here we go:
1. remove the 2 small caps in the doorhandle, so you can access 2 torx screws that hold the doorhandle section into place.
(I used a 'modified' fork to remove the caps)
2. after removing the torx screws, lift the doorhandle section.
3. unclip the wire from the door opening/locking-mechanism and unplug the connector from the switches, so
you can remove the doorhandle section from the door/panel.
4. remove the 3rd torx screw.
5. gently slide a panel removal tool (highly recommended for this job) between the door and the inner panel.
The inner panel is fixed really tight to the door by MANY (11) plastic clips and it will take some effort to get it loose.
I found it easiest to start loosening the clips on the side of the doorpanel and then work your way down.
Once you have loosened about 5 or 6 clips, you can firmly pull the panel to unclip the rest.
In my case some of the clips snapped/broke during removal, but could still be re-used.
6. Loosen the seperate top section of the panel by firmly pulling it (and then just leave it hanging loose.)
It's held in place by 3 metal clips.
Once everything is loose and/or out of the way, push the inner doorpanel up slightly so it unhooks from the window area
and you will be able to remove the panel from the door.
NB: If some of the clips snapped during removal, remove these from the door first and (if possible) attach these back onto
the now removed doorpanel
7. unplug the connector from the speaker and drill out the 3 rivets, so the standard speaker/housing can be removed.
8. install the new speaker.
I used 20cm/8" pioneer speakers and depending on the type/model speakers you install, you will have to drill 3 or 4 new holes to
be able to fix it the door.
I also cut off the old standard speaker connector and soldered the wires straight to the new speakers.
9. Test the new speaker and if everything works as desired, you can install the doorpanel back in place (using the reverse order of this removal procedure)
Hope this helps.
-Eric