Use a dynamat trunk kit.
First find the source of the rattle then determine what steps to take to stop it.
my experience in stereo work you get the deepest bass with the subs facing the open trunk area
Maybe its the dashboard if the rattle is inside. I hear the same rattle when I hit a bump.
Dynamat
rivits in bumper are loose
best place to put it is in the trunk.if your car is older and kinda a beater then your trunk might rattle a lot.
Squeaking usually caused by vibration Anti-rattle clips (if any) installed? A paste type compound is available to stop rattle
The possessive form for "the rattle of the snake" is the snake's rattle.
Too Much Bass or a Bad Switch.
Bass is low frequency,just like an earthquake.It's going to make anything rattle that isn't securely fastened.Then it will try to loosen it up again.Tighten the speaker down as best you can then see if that helps you.
The trunk of your car is the best place to mount a pair of subs. The trunk also acts like a sound chamber for the subs. Just make sure you seal the trunk good so it will not raddle when the bass hits.