SV6 SPEAKERS?

[Eh VZ Arch]

Hi all, first post so be kind Had a double din head unit fitted by Car Audio Shop. I supplied head unit and all necessary Aero wiring, facia etc. The problem is sound is only coming from speakers in front and rear doors, no sound from rear deck speakers. Has he wired it wrong or will it need an amp to fix the problem or perhaps something else? Taking the car back this week but don't want to spend more to fix the problem if I don't have to.
TIA Archie

 

[Fu Manchu]

Do you have the rear speakers?
Have a look up underneath the boot at the underside of the parcel shelf.

The spaces are utilised for factory 8" subwoofers and amp.
Almost the same as the ones in VE.

Calais and up spec models had them.