Hating to cut holes in my boat, I was able to position the cockpit speakers in the base of the table such that the only hole in the cockpit decking was 1/4" (6.35 mm) instead of 4" (101.6 mm).
I first installed an upgrade to the radio: a SONY GT57UP car stereo with AM/FM/CD/USB/MP3 and SIRIUS capable to replace the original AM/FM/tape deck radio.
The wire harness was not a big deal. Use a 9 volt battery to find the wires that are the speaker wires.
Threading the 2 sets of paired wires to the cockpit speakers via the small space between the cockpit deck and the aft cabin ceiling tool some time and patience. But well worth it. The speaker wires go aft, then through the bilge just forward of the aft cabin door then into the engine room, up and aft and there is an access hole (covered in the picture) through which with some frustration the wires can be snagged and a connection made with the wires from the speakers that have been led through the 1/4" hole in the deck inside the table base.
Hope the pictures do justice. Roger Howard
There is also a discussion on cockpit speaker options on the Jeanneau Forum see: Cockpit Speakers