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<blockquote data-quote="bubbagumper6" data-source="post: 8253424" data-attributes="member: 567719">I&#039;ve seen this before.&nbsp; Issue is from an unbounded feedback loop.&nbsp; When you close the door hard it creates a slight pressure wave in the vehicle which will move the cones of all speakers that share that airspace.&nbsp; Basic electrical theory says when you move a coil inside a magnetic field it generates a voltage, this voltage goes to your line out converter which gets amplified and then causes your subwoofer to &#039;thump&#039;.&nbsp; This thump creates a slightly larger pressure wave and the whole process starts over again until it reaches the point where they equalize and the volume stops increasing.The problem is that you&#039;re still supplying the LOC and amplifier with power but no signal.&nbsp; When the signal source (factory HU) is on, even if you&#039;re not playing anything it&#039;s holding the signal at 0V.&nbsp; When it&#039;s turned off you&#039;re essentially &#039;floating&#039; the signal and it&#039;s allowed to fluctuate from outside sources.&nbsp; You need to find a new power source for the amplifier so it&#039;s shut off when the signal source is shut off.</blockquote>

[QUOTE="bubbagumper6, post: 8253424, member: 567719"] I've seen this before. Issue is from an unbounded feedback loop. When you close the door hard it creates a slight pressure wave in the vehicle which will move the cones of all speakers that share that airspace. Basic electrical theory says when you move a coil inside a magnetic field it generates a voltage, this voltage goes to your line out converter which gets amplified and then causes your subwoofer to 'thump'. This thump creates a slightly larger pressure wave and the whole process starts over again until it reaches the point where they equalize and the volume stops increasing. The problem is that you're still supplying the LOC and amplifier with power but no signal. When the signal source (factory HU) is on, even if you're not playing anything it's holding the signal at 0V. When it's turned off you're essentially 'floating' the signal and it's allowed to fluctuate from outside sources. You need to find a new power source for the amplifier so it's shut off when the signal source is shut off. [/QUOTE]

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