subwoofer makes pop noise?

Hey guys,..I just got an Alpine CDA-9886 installed in my 1994 LS 400 Lexus. -- Had them wire it to the factory speakers (factory amp that leads to factory 8" sub).It looks great, sounds great, and overall I love it.However, the sub 'pops' when you turn the car off. It sounds just like if you were to unplug or plug in an RCA input to say a Powered Floor Subwoofer on your home theater setup. That is the best way I can describe the sound.The only thing I know the installer did a little different was he wanted to give the factory sub a little more punch because it wasn't hitting as hard as it did with the factory head unit after he put in the Alpine -- So he got this little red (I think red) box and installed in inline to the sub. He said it was like a mini amplifier.. and sure enough it gave the sub woofer a little more punch.Surely I don't have get that piece removed to take away this 'pop' on the sub when you cut the ignition off? -- is there anything you guys can think of that I could do.. Or take it back to the installer and tell him this is what I've been told is a good thing to try to remove that pop.When I left I wasn't aware of the pop.. so if I heard it I would have mentioned it then. Hopefully this is a common thing that you experts can say .. yeah thats no big deal this is probably happening.. just change this wire to this.. or add this isolater thingy inline here.. etc.Again the speakers are factory, and it consists of this:4 Door speakers, all are 4inch. (These speakers are not amped factory, they are amped by head unit) .Then there is a 5th speaker, which is the sub woofer (8inches) that is free-air/IB factory that is powered by a factory Pioneer amplifier at about 40watts. (Sub comes up from trunk and sits in front of the third break light on the deck behind the backseat. (Has a cover etc).Thanks for any help! I will monitor this thread, and hopefully I can get an idea and take it back today and get something quick done to it , to take that *pop* out of it.I'd prefer not to remove whatever that inline amp red box thing is, because it really makes the factory sub sound better.the unit, if you are familiar with the Alpine CDA-9886 has independent controls for the sub, and a crossover built in. He wired it up where it actually works on the sub.. (I guess because it already had a factory amp.. ) -- He said he probably wouldn't be able to get that part to work with the factory sub, but it ended up working anyway.Here's a pic or two if it helps..and we ran the ipod extension and a USB extension to console which is handy:Thanks so much-Neofate

Does this ONLY happen when you turn the car off? Does it do it when you turn the headunit off? It could be that the factory amp is keeping a small amount of power inside when the car is turned off thus causing it to make the sub pop. It could be getting a spike when the car is turned off. I get a spike in my speakers when I turn my headunit on. I dont get it when I turn the car on. But if I have the car on, then turn my headunit on, I get a pop. Its a spike. It wont hurt the sub though.

A "mini amplifier"?  Not a good idea.  The factory sub uses a factory amp and should not have any sort of power booster applied to it.  Go back and have them remove the "little red box" thingy.  If you insist on using the factory speakers, you will have to live with the quality trade offs that implies.  If I was you, I'd replace of them all as soon as you can afford to do so.Support the12volt.com

I would first do what Dyohn said about taking it back to get the booster removed. That might be causing the amp to pop. If that isnt the cause, then you simply have a spike caused by the amp staying on for a split second longer than when the vehicle is turned off. The amp gives off that spike through the output of the sub.