Just purchased the Sharp 70" 847U. Watched first 3D movie and noticed we can't sync 3d while sitting on a couch directly in front of the TV. If we stand in front or go to the side 3D says in sync. So i measured precisely when 3d drops out. If I go from a sitting position to standing there is a very dicrete level (42") off the floor when sync'g happens, crouch down to sitting and no sync. So there is a dead zone right where they tell you to view 3D. Moved the center speaker and pulled all misc obstructions away from the TV front and still the very desecrate dead zone. The TV sits on its factory stand on a cabinet ~24" high. Any help?