I bought some new 9*6 speakers to hook up in the back 8.5 cm instalation depth.
Ive seen there might be a problem because it is not deep enough.
Is here someone who installed boxes and can help me ?
Without cutting into the sheetmetal supports, the largest speaker that will fit in the rear hatrack is 6.5" To go to 6 x 9, a minor amount of metal trimming from the trunk side will allow a flush mount. If you don't want to cut, there are commercial speaker risers that will lift the speaker up off the deck, or you can scavange the risers from a 1989 Honda Accord or check the boxes from a Mitsubishi Diamante.