lexus install issues

[chrisw91 10+ year member]

did an install on my roomates IS250 with a single 8 and and jbl mono amp. everything else is left original, so i used a line out converter. i got the signal for the LOC from the factory sub, its power and ground are supplied from the amp... now the issue, only after starting the car and shutting it off. once you get out and close door, the sub starts playing a continuous tone, until you open the door it stops. then will start again after closing door. i played with variables, if i close door softly it will not do it. can bang my hand on outside of car and it will start doing it. so i feel like it has something to do with the security, but it is not tied in with security anywhere. any ideas? or ever heard of this issue?

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[fasfocus00 5,000+ posts]

probably have a pinched wire somewhere causing this. I'd re-check all the wires to make sure there's not pinching or arching anywhere. anywhere there is more than one electrical connection, I'd cover with electrical tape just in case.

 

[paulturner911]

Can anyone provid a picture of the factory am and the correct wires to tap?

Im having an issue getting sub signal to my LOC on a 2014 IS250. Ive got the amp powering up, just cant get audio correctly to the LOC.

Thanks

 

[bubbagumper6 5,000+ posts]

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.