Need help with loud thump/thud coming from subwoofer

[hoy128]

My Setup:

2005 Acura RL factory Bose head unit

JL Audio 12W6V2 in basic enclosure

Alpine PDX-1.600 amp

I've had this setup for the past 4 years and just this past week I've been running into an issue I haven't come across before in any of my previous systems. The problem seems very random so it's difficult for me to just bring it to a shop to check out. There is a crazy loud thud/thump coming out of my subwoofer, sometimes 5-6 times and hour, sometimes once a day, sometimes nothing for a couple of days. The thump/thud is loud enough to shake the entire car and lasts for about a second. It doesn't matter if the car is in park, if the audio is turned up or down, heck....it even happens if I turn off the stereo head unit. The thump/thud is always the same volume regardless of the state of the stereo.

Has anyone come across this before or have any suggestions on what I can do? I'd hate to bring it down to a shop and pay them to look at it to be told "looks good to me."

Thanks in advanced!

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[CrossoverOre 10+ year member]

what do you have in there feeding the signal from the factory head to the amp?

 

[Andrew12 10+ year member]

Sounds like maybe a ground is coming loose

 

[hoy128]

Oops sorry, I have a line out converter, i think that's what it's called, connecting the RCAs to the back of my head unit. I had it installed at a shop so they basically sold me what I needed. I'm thinking it is it is a wiring issue too, possible a loose cable but I checked all the connections that I could physically get to. Logically, I cant think of my head unit as being the issue since it happens even when the radio is completely off.

 

[Andrew12 10+ year member]

Can you find where your amp is grounded to the frame of the car?

 

[hoy128]

Thanks for the suggestion Andrew. I'll see if I can figure out how to pull the backing off my trunk out this weekend to check. They wired it pretty cleanly so all the wires disappear behind the walls. You hunch is what I was thinking too but I just wasn't sure what wire. The ground wire makes a lot of sense!

 

[CrossoverOre 10+ year member]

I dont think it would be the ground if the problem happens when the stereo is off. I would look into the loc. and also how they have the remote connected and what to. My gut tells me its the loc. Some loc's have a remote output option that triggers off the signal coming through the loc. Sometimes those will keep the amp on when it should be off. The more I think about it the more I want to blame the loc as the problem. But just as a test smack the amp and see if the subs will thump at you theres a chance there could be an internal issue with the amp.

 

[hoy128]

Thanks so much for the recommendation guys! I'm going to look at all these this weekend to hopefully find the problem.

 

[hoy128]

well crap, I thought they installed a LOC in my car but I followed the RCA's and they tap into my stock amp. Smacked the AMP around but it doesn't cause that thump. I tried following the remote cable from the amp but it disappears under the rear seat. Need to try to figure out where the heck that remote cable goes. The ground cable seemed secure to the chassis with no obstructions. The things we do for good audio hahaha....