a6 with Bose ... and symphony one

i had to replace a couple of speakers which started cuting out and when doing my testing of the new speakers noticed soemthing odd .. when faded to the back if i switch the balance between drivers and pasenger i notice lots of subwoofer when coming from paseneger side but when i switch to drivers I have no sub output at all ..

does anyone know how this is wired .. is there a sub for each side or is it only wired into the paseneger side ..

I guess the follow up question would be how do i get it out .. looks well tucked into wheel well area of pasenger side trunk ..

All the best