What exactly does bottoming out a sub mean?

[alec14]

Not to thread jack. But how could you tell if a sub is bottoming out, would it make a bit of a slap sound? When my sub hits really low it seems to make a weird noise, which I have been told is normal, but I'm thinking the stereo shop might want me to blow it and buy a new sub from them. Its also in a sealed box.

good question, i don't mind at all! i was wondering that too after you asked it. lol

[alec14]

A coil bottoming against the back plate is typically very loud.

As Corey mentioned there is also a spider glue joint vs. top plate bottom as well.

is the spider glue joint bottom out be loud as well? would it be noticeable?