Yes on the standard setup on vans & kombis, there are four speaker inputs on the back of the stereos - front left/right which are used & rear left/right which are empty
You need to install additional wires to new speaker location, remove stereo and fit new cables into the empty terminals on the existing quadlock connector on rear
Heres the connector before i added my rear speakers
View attachment 379
and heres one of the wires with pin connected on end ready to insert into plug assembly
View attachment 380
Its worth noting that after connecting additional speakers in they will work but to function properly the radio will need to be coded with VCDS (vagcom) to accept new speakers and this will activate the fader/balance menu in the radio to give you additional adjustments
@shylock i have VCDS if you would like speakers coded