sub hitting on its own

[hari-bhari]

Ok so I've got a 2000 solara with a stock headunit, run through a navone LOC and into an mtx 4 channel amp. the amp then powers a set of BA RC620s up front and the rear channels are bridged to an MTX 12" sub in the trunk. Positive power wire is run up from the battery and negative is grounded to a spot a few feet away in the trunk which has been sanded down. Accessory wire is run from the headunit. Power wires are run on the right side of the car and speaker wire is run on the left. Normally everything sounds great and clean, although this is still some hissing from the speakers at high volumes, but I'll attribute that to the stock HU (which I dont want to swap out for fear of theft). My problem is as follows:

-Whenever the headunit is turned off, the sub starts resonating on its own.
-I have a gain control knob run up to the front, and when I turn it up, the resonance is louder, and when I turn it down, it gets softer. However, it will not go away completely.
-If the doors are open when I switch the headunit off, the sub doesnt do anything, but as soon as I shut the doors, the sub starts hitting.
-Also, if both doors are closed, and I switch the headunit off, sometimes it resonates and sometimes it doesnt.
-If I switch the headunit off, and I open and shut either door, the sub will start hitting on its own.
-If I leave the headunit on and turn the volume all the way down, there is no problem.
-When the headunit is shut off, I can also hear the faintest noise or interference coming from my tweeters in front, but you can only hear it in complete silence with the engine off.
-It doesnt matter what position the ignition is on (ON, ACC) or if the car is running, all problems remain the same.

I have opened everything up and had a look at it, and I can't seem to find what would be the matter. Any help is greatly appreciated. Thank you.

[OKANG]

Sounds like ground loop interference:
http://www.bcae1.com/glisoltr.htm

Something like this should fix it:
http://www.xitel.com/product_gli.htm

Also, make sure you've got good grounds. They should be as short as possible, on bare metal, and use the same guage as the power wire.

[B_Master_Flash]

Ok so I've got a 2000 solara with a stock headunit, run through a navone LOC and into an mtx 4 channel amp. the amp then powers a set of BA RC620s up front and the rear channels are bridged to an MTX 12" sub in the trunk. Positive power wire is run up from the battery and negative is grounded to a spot a few feet away in the trunk which has been sanded down. Accessory wire is run from the headunit. Power wires are run on the right side of the car and speaker wire is run on the left. Normally everything sounds great and clean, although this is still some hissing from the speakers at high volumes, but I'll attribute that to the stock HU (which I dont want to swap out for fear of theft). My problem is as follows:

-Whenever the headunit is turned off, the sub starts resonating on its own.
-I have a gain control knob run up to the front, and when I turn it up, the resonance is louder, and when I turn it down, it gets softer. However, it will not go away completely.
-If the doors are open when I switch the headunit off, the sub doesnt do anything, but as soon as I shut the doors, the sub starts hitting.
-Also, if both doors are closed, and I switch the headunit off, sometimes it resonates and sometimes it doesnt.
-If I switch the headunit off, and I open and shut either door, the sub will start hitting on its own.
-If I leave the headunit on and turn the volume all the way down, there is no problem.
-When the headunit is shut off, I can also hear the faintest noise or interference coming from my tweeters in front, but you can only hear it in complete silence with the engine off.
-It doesnt matter what position the ignition is on (ON, ACC) or if the car is running, all problems remain the same.

I have opened everything up and had a look at it, and I can't seem to find what would be the matter. Any help is greatly appreciated. Thank you.

1st of all, your remote wire is wired incorrectly. Done properly, the amp should turn off when the H/U is turned off which would make it basically impossible to have the interference you're talking about. As long as all of this only happens when the H/U is off, fixing the remote wire will solve your problem. If you're having interference while listening to music also, you prolly have a problem with your ground or RCAs/LOC

[krawzyazn]

gain is too high

[hari-bhari]

gain is too high

my gain is all the way down. but yes my remote wire needs to be changed.