why does my sub "thump" when i turn it off?!

[Simon13]

I've just refitted the sub and every time you turn the ignition off it thumps quite loud. if you know what i mean. It never did this before?

I took a picture to be sure to wire it back in properly!

[Jim320i]

Is the power line cable to the amp fitted away from the signal/sound cables? I.E on opposite sides of the car?

[zaust]

Bad eart either on the stereo or the amp or both.

[pac1982]

Bad eart either on the stereo or the amp or both.

+1 a bad earth can cause this, not only that but improving your earth will be one of the best things you can do on an ICE install

[Barx325i]

also, your earth connection wants to be as short as practically possible

[chu346]

This can be caused by using the wrong remote from your headunit if it has more than one remote wire or if you use the ignition live and the sub amp will either turn on too early or late.

[Simon13]

I didn't fit this ICE install to the car so i've no idea how its all been done. So i suppose i'll have to investigate. Apart from being annoying it won't be causing damage will it?

[mrLEE30]

have you wired the remote to the head unit ariel signal wire by mistake?

i asusme you have head unit and an amp, with the sub run from the amp?

does it thump if you turn off the head unit?

Assuming the thump is not louder then the volume on about half then it will not damage the speaker

[miniblob]

As MrLee said!!!!!!!

Shouldn't cause any damage!!!
Normally indicates equipment being switched in the wrong order - i.e. the sub amp should be switched off before the h/u to avoid the 'thump'.

As said, double check the remote lead from the h/u to the amp is connected to the right one - should (normally, i think!!) be a blue lead coming from the back of the h/u.
The electric ariel one may well do a similar job, but with a delay when you turn off the h/u, allowing time for the ariel to retract!!

A dodgy connection there, or a dodgy earth, would also give problems while it's on/playing - cutting out, humming, etc! As with power/speaker/signal cables run together, worst case would just be interference, whistling, humming, etc!!