2002 qx4 radio aftermarket radio sounds low

[mark19782075]

i bought a 2002 qx4 and the raio was loud but only the front speakers worked took it to a guy i know and he made all the speakers work but now i can crank it all the way up and it sounds low he told me it can be the radio or the amp how do u check wich one it is need hellp asap

[Jesda]

Did he run new wires from the head unit to the speakers or did he integrate the Bose amp?