i had lg 6900r system installed professionally and added two extra speakers behind the seats.in my porsche boxter. the the front speakers keep cutting out then most un expectley just turns on but the rear additional speakers dont turn off when the front speakers stop working i loose the voice of the sat nav,then sometimes the lot turn off on its on reboot, then start again.no one can work out why?i also looking where to download free manual,nd cd,pl advice i am willing to pay for the cd