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flappijs

Subwoofer thumping

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Hello everyone.

So , I bought audi a6 c5 avant some while ago and it had some cheap chinese headunit ,so I decided to replace it with Pioneer MVH-190UB,everything was good but then I wanted little bit more bass in the car so I bought subwoofer and installed it ,everything was fine ,there wasnt any noises when the music was playing and so on.

 

Then I had to change trunk lid because it was too rusted out, but because of the subwoofer ,i wasnt able to place in it the trunk so I removed the sub, just the box ,left the + and - for the sub just in the trunk togheter with amp.Changed the trunk ,got home and hooked up the sub and it was starting to make the thump noise,hearthbeating or how you call it. So I thought I f'd something with the trunk lid wiring when placing it back togheter , somewire touching or something, so I took the plastics off and inspected the wiring and it looked good so then I unplugged all the things (number plate lights, fog lights and so on ) so then I started to think it isnt because of the trunk lid change.

 

So ,I started attacking the amplifer wires. So the thing is when I turn down the gain ,it isnt making the noise, when I turn it up a little ,it starts doing it the thump again.To make sure the amp wasnt fried I hooked it up to friends car and everything was fine in his car so then I was left with RCA's , the ground wire and the source. So I changed the ground location 3 times and still was the thump so I kinda decided its not the ground, the source wire had good voltage when measuring with multimeter so not the source so ,the RCA's are left. Took them out because I thought maybe some because of other wires there are some signals ''entering'' the RCA's but still, so ,tried my friends RCA's ,still the thump. So next thing I did,was took jumper cables and connected the source and ground directly from battery to amp and it was fine ,no thumping, so to find out which wire was the ''bad'' one I tried only with the source ,but the thump was back ,tried only ground and thump went away. So now I know that there is some problem with the ground.At first I thought its the ground wire itself, but it isnt because I took the jumpercable and attached it to the ground wire place where it was and still got the thump. So know I don't know what should I do ,and why it suddenly got bad.

 

Thats kinda long story and my english isnt that great so excuse me if some parts arent understandable but I hope I explained enough for you to understand whats really the problem.

I hope someone can help me with this . :)

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Was the amp still turning on when you removed the sub and left the bare wires in the box?

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Yes, and thats probably the reason(atleast I think so ) ,because I had to drive from home to garage and I was listening to music when driving and the amp was still completely hooked up ,just the wires from the sub were removed.

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So you completely removed the wires from the amp? Or did you just disconnect the box and remove it?

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Posted (edited)

I have passive subwoofer .

The amplifier was left in the car , but the subwoofer box was taken out. The wire from amplifier to the subwoofer (the +and -one for speaker) is the one I disconnected from the subwoofer side and left the wires in car , I dont know if they touched when driving or not.

 

EDIT : Just now remebered that I didnt mention the thump goes away when I unplug the RCA's.

Edited by flappijs

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i had seen this symptom before , it was cured when i grounded the rca on the back of the radio

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i had seen this symptom before , it was cured when i grounded the rca on the back of the radio

 

This^^^ pioneer radio, I've experienced this... something about a pic fuse wish I could be more help

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Yeah, was reading through the forums and saw that some people had problems and fixed with grounding RCA's , so after writing when I remove the RCA's the thumping stops I thought I should try it too ,havent it tested yet, but if I understand it right, I just wrap some thin wire around the RCA's outer shell and then the other end of wire attach to radio case right ?

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i think there is a bolt on the back of the radio you can ring terminal too

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Being pioneer most likely the internal pico fuse is shot ..grounding the rcas usually helps but doesn’t get rid of the noise all the way ..Pioneer wants more than the decks are worth to fix the issue

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Finally got time to try ground the RCA's ,aaaaaand it works now,no more thumping.

Thanks for the help . :)

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sweet

 

with pioneer i always remove the RCA's before connecting or disconnecting power .

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