Sub thumps when car is turned off

[frosty3777]

When i turn the car off, the sub thumps. Also, when i turn the high beams on, the sub thumps. What did i do wrong. How can i fix this.
THanks
Sam

[Taiko]

My sub at home does this too. I have very limited knowledge of car audio, but do you have a cap in your system? If you do, might it be that discharging?

[frosty3777]

My sub at home does this too. I have very limited knowledge of car audio, but do you have a cap in your system? If you do, might it be that discharging?

No cap in my car. TO me, it seems that it has to be a wiring problem. i am thinking that maybe a wire is crossed over another or is too close to a certain wire, but i'm not sure.