Knocking Under Passenger Seat

[charlyjo]

as title post knocking under the drivers seat, only does it when the cars cold, at first thought it was the sub but still does it with the radio off, been underneath to check all the heat shield's etc and they are all tight, was thinking it may be the baffles in the exhaust but theres no rattle just a knocking till the cars warmed up,

many thanks in advance for solutions especially the right on e