subwoofer pops when turned off

My subwoofer pops when I turn off the car, but not when I turn it on. Also, if I turn off the sub amp while it's still receiving a signal it doesn't pop. I've done some searching and found some info on delay circuits that keep the signal source on for a second or so longer than the subwoofer amplifier. The how-to from Crutchfield only describes the diode and cap, but the diagram shows a transistor and relay, which is correct? http://www.crutchfield.com/S-Pl4IZ8wECqa/tech/kb327.html Also, this post only describes using a diode and cap. https://www.the12volt.com/installbay/forum_posts.asp?tid=7885&KW=turn+on+pop+velocity

1998 Volvo V70, aftermarket head unit and subwoofer.

I tried it connected to a switched wire from the car and the remote turn on on the head unit, no difference. So according to your diagram I just need the diode and cap?

I tried the circuit in your diagram and it keeps burning up (literally) the capacitor. The one I used was 470uf 35v based on the crutchfield explanation.

You have the capacitor connected backwards.  There shoud be markings on the side that signify the negative terminal.  Make sure you have the negative terminal of the capacitor connected to ground.   If it is heating up, this is the only thing that can cause that.

Thanks, now I feel like an idiot.

Works perfectly now, thanks.