there are total 4 speakers in Passo. (2 in the dashboard, and 2 in rear doors)
the dashboard ones are 4 inch size (pre-installed in Passo by factory)
the rear doors ones are 6 inch round size (there are no speakers pre-installed, so you will have to install by yourself)
for installation of 6x9, there is no space, you need to install them in boxes, and can fix them anywhere in trunk etc.
