Subwoofer thump

[rescfrmn]

Recently installed a UAS 8.4 with CarPlay. 2nd upgrade. 1st was a Harman 8.4 from 5" screen in a 2017 tradesman. The only issue that I have created is that I now have a subwoofer heartbeat thump when I turn on the vehicle. I can disconnect the lineout convertor plug on my amp and it goes away and begins to work again. But this happens each time I turn the vehicle off and restart it. Any suggestions?

 

[Atcer2018]

Recently installed a UAS 8.4 with CarPlay. 2nd upgrade. 1st was a Harman 8.4 from 5" screen in a 2017 tradesman. The only issue that I have created is that I now have a subwoofer heartbeat thump when I turn on the vehicle. I can disconnect the lineout convertor plug on my amp and it goes away and begins to work again. But this happens each time I turn the vehicle off and restart it. Any suggestions?

Many questions for you. Why are you using a LOC? Aftermarket sub and amp? Where is the LOC drawing power? Is it a high level input to an RCA out? Type of sub amp? Where are you drawing the signal for the LOC? There are lots of questions but the most common for aftermarket subs and amps is the the grounds for the amp and LOC, quality of the LOC power feed and what signal you are using as the trigger for the LOC. Additionally some aftermarket amps just don’t do a good job of controlling the on or off thump.

 

[rescfrmn]

I am sorry. I was thinking about another truck. This truck has high level input wiring to the amplifier. No RCA's. So, I am not using a line out converter. Yes, aftermarket subs and amp. I have the high-level input wiring connected to the rear speaker wiring at the B-pillar posts. This is not only the on or off thump. This is a consistent heartbeat type thump until I disconnect the high-level input connector at the amp with the vehicle running. If I don't disconnect it while the vehicle is running and reconnect it the thumping starts whenever I start the truck. It is consistent every few seconds and then repeats. I have noticed that it also shuts down the output from the rear door speakers until I disconnect and reconnect the high-level input connector.

 

[Black-Wolf]

I am sorry. I was thinking about another truck. This truck has high level input wiring to the amplifier. No RCA's. So, I am not using a line out converter. Yes, aftermarket subs and amp. I have the high-level input wiring connected to the rear speaker wiring at the B-pillar posts. This is not only the on or off thump. This is a consistent heartbeat type thump until I disconnect the high-level input connector at the amp with the vehicle running. If I don't disconnect it while the vehicle is running and reconnect it the thumping starts whenever I start the truck. It is consistent every few seconds and then repeats. I have noticed that it also shuts down the output from the rear door speakers until I disconnect and reconnect the high-level input connector.

Sounds like you have some sort of feedback loop going. Can you record and share a video + audio using your phone, say on Google Drive or similar, so someone can listen to exactly what is going on?

 

[rescfrmn]

I will try

 

[Atcer2018]

+1 on what Black-Wolf stated. It sounds like a ground loop feedback if you have a rhythmic thump. Can you verify you are still speaking of a 2017 Tradesman as that is a 4th gen truck without ANC and a different truck may have ANC circuitry. If the head unit is shutting down the rear channel that you are using for the sub feed it’s not seeing a load and will shut down that channel. The key part in what you’ve told us appears to be the LOC. Could be defective or a poor power feed source. The ground loop is typically from a poor ground. It needs a good chassis ground preferably close to the ground you are using for the sub amp. That said are you using a dedicated sub and amp or a new all in one self contained unit. Does the sub amp/unit accept high level inputs? If it does you could try the system without using the LOC. A lot of newer amps will show a load to the head unit on the high levels so the channel won’t be shut down.

 

[zrock]

sounds like a bad ground or bad power feed are they running close to any of the factory wiring? Usually you want to keep you wiring away from any factory wiring so it does not pick up any noise. Also are you power and ground the proper gauge for the length of run you are doing? I have had these issues before and have only ran across one when i had to put a ground isolator in the system as something else had a issue in the truck.

 

[rescfrmn]

There is not a LOC being used. That was my mistake. I am using high level input wiring. Yes 2017 Tradesman. This occurred after moving from the 8.4 Harman radio to the Panasonic. Subs and amp were in use with the Harman and the only change was moving to the Panasonic 8.4. Separate subs and amp. They have been in the truck for over a year and a half. This is a rhythmic thump like a heartbeat. Goes away after removing the high level input connector and reconnecting.

 

[Atcer2018]

There is not a LOC being used. That was my mistake. I am using high level input wiring. Yes 2017 Tradesman. This occurred after moving from the 8.4 Harman radio to the Panasonic. Subs and amp were in use with the Harman and the only change was moving to the Panasonic 8.4. Separate subs and amp. They have been in the truck for over a year and a half. This is a rhythmic thump like a heartbeat. Goes away after removing the high level input connector and reconnecting.

Like zrock said, check the power and ground connections. The ground needs to be to the chassis like a seat anchor bolt or a bolt to the chassis under the dash. Keep the wire as short as possible and the proper gauge. How do you have the power connected? From the battery or from wire splice in the factory wiring? As an experiment you could try running a power wire directly to the battery with a length of any decent gauge wire right out the door opening directly to the battery and power up the system even at very low power you should be able to detect if the thump is still there. This will give you an indication if your power feed source is poor. It could also be the circuitry went bad in the amp. Something could have fried or maybe your particular amp does not show a load to the head unit and you are getting the feedback loop through that channel instead. This can be corrected with inline resistors to show a load on the speaker feed side of the amp.

 

[rescfrmn]

Power is directly to the battery. Ground is about 13 inches long to the seat to body bolt.

 

[Atcer2018]

Power is directly to the battery. Ground is about 13 inches long to the seat to body bolt.

My best guess then is the newer Panasonic head unit has the shut down circuitry to cut power to any speaker that doesn’t show a load. The older Harmon units probably didn’t have that. You probably get the heartbeat thump because the head unit isn’t seeing it as an active channel and the result is passive feedback when the channel is shut off. You stated the heartbeat goes away if you remove the inputs from the amp and reconnect them while powered up? That removal and reconnect is then signaling a load to the head unit because it’s got power. Your amp may be older and absent the load signal circuitry. I’ve read that some folks with newer amps that have the load signal circuit still have issues with the newer Panasonic head units. They make inline load resistors that will provide this function. They are pretty inexpensive and can be found on Amazon and eBay or most car audio stores. You may be able to get a pair at a local installation place. Unfortunately I have no experience with the audio inline load resistors or the load that the Panasonic head unit requires. I have a Kicker amp and it does a good job of load signaling to my 2018 Panasonic head unit so it’s a bridge I never had to cross. If you use Amazon you can find the load resistors there specifically for 2018 and up Chrysler radios which would include the Panasonic head unit. They are $15 and you can return them if it doesn’t solve your issue.