Subwoofer makes shaking tinfoil noise

[e2theloc]

When my orion hcca hits lows it's making a funny noise i can only describe as someone shaking a sheet of tinfoil. Could it be the spyders have came loose or something? idk anyone ever heard this noise?

[Boon]

Could be loads of things, including your coil hitting the back plate.

[Loudcivic]

does it kinda sound like a slinky in a way. coil could have came unwound