# Sub pops when my car is turned off.



## dubuang (Feb 19, 2014)

I asked a few of my buddies why my sub would make a pop when I turned off my car and they told me to check the grounds. So I stripped my car and 're-sanded where my ground was and bolted it back up. 

It didn't work, my sub still makes a pop when I turn off my car. I tried turning off the HU and then turning off the ignition, but it still would pop even if the HU was off. I'm running a stock head unit, an audio control LC6i, connected to a zapco ref 500m, any help is appreciated.


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## jb4674 (Jan 29, 2015)

Sounds like the remote out (GTO) isn't working properly. Try unhooking the remote wire going into the LC6i and split it to run two leads (one for the LC6i and one for the amp) and see if the problem goes away. If you do this, don't use the remote out from the LC6i to the amp because you won't need it at that point.


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## dubuang (Feb 19, 2014)

jb4674 said:


> Sounds like the remote out (GTO) isn't working properly. Try unhooking the remote wire going into the LC6i and split it to run two leads (one for the LC6i and one for the amp) and see if the problem goes away. If you do this, don't use the remote out from the LC6i to the amp because you won't need it at that point.


Can you elaborate on why this would work being that the remote works just how it is set? Amp turns on and off when the 12v signal is on and off, so how would tapping into the source make a difference? I'm just wondering because I'm going to try a new ground spot at the moment and if it doesn't work I'll try what you suggested, but I don't see how it would change anything.


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## subterFUSE (Sep 21, 2009)

Turn off pops are not caused by your grounds, so don't waste any more time checking those. They are caused by amplifier design, specifically a lack of a soft turn on/off feature.

Ever notice how home audio amplifiers take a few seconds to power on? You click the power button, and the lights come on.... but no sound for a few seconds until you hear this "click" inside the amp. That click is a relay inside the amplifier which prevents signal from getting to the speakers until the amp has powered on fully. And when you turn the amp off, is goes through the process in reverse. Speaker signal gets cut but the amp still has power for a couple seconds, then it get shut off.

That relay is actually on the speaker connections, too. I have seen people try to use relays on the remote wires to the amps, but that doesn't actually work. You need the amp to power on after the sources units, but even when it turns on you do not want to send signal to the speakers until it has fully powered up. Then, when you turn off, you need the speaker signal stopped and then the amp to shut off, and then the DSP, etc.. The process is reversed.

Some car audio amps have this feature, but most do not.

Some of the DSP units out there have a timed remote output which is intended to take care of this, but they actually don't work very well.... because they are basically just relays on the remote wire. A relay on the speaker wires is the real solution, as far as I understand.


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## subterFUSE (Sep 21, 2009)

Sure enough, as soon as I speak on this topic I run into it myself. 

My newly installed Helix DSP Pro is causing turn-on and turn-off pops in my system. At first, I was worried the amps were causing the noise. But when I disconnected the RCA cables from the DSP to the amps there were no pops. But if the DSP is in the signal chain, thumps on startup and shutdown.

I'll report back when I get time to test more.


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## dubuang (Feb 19, 2014)

I'm kind of stumped I don't know what's causing my turn off pop...


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## subterFUSE (Sep 21, 2009)

dubuang said:


> I'm kind of stumped I don't know what's causing my turn off pop...


Let me suggest the following test:


Unplug your RCA cables from the amplifier. Leave all other cables connected.

Turn on the car and listen for a turn on pop. Then wait about 30 seconds and turn off the car. Listen for a turn off pop.


If you get no pops during the above test, then the issue is the DSP and not the amps.


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## gregerst22 (Dec 18, 2012)

What can be causing this is the audio signal before the amp is shutting off before the amplifier(s) turn off. This causes the popping sound. More than likely the DSP is turning off before the amps. This is sorta like yanking the RCA cables to the amp while the system is running. The amps need to turn off before the dsp does.


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## sqshoestring (Jun 19, 2007)

Likely something to do with how the RCA shielding is handled. Not sure how you would fix it depends on your equipment, but some searching might find you something. (If it vanishes with the cables unhooked)


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## gregerst22 (Dec 18, 2012)

btw I had this same issue with my Helix. Configuring it so the amps turned off before the dsp fixed it.


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## dubuang (Feb 19, 2014)

subterFUSE said:


> Let me suggest the following test:
> 
> 
> Unplug your RCA cables from the amplifier. Leave all other cables connected.
> ...


Thanks I'll try this tomorrow morning... I ended up hooking everything back up because I got fed it with it. I'll try tomorrow for sure though so I can see if it's the DSP.


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## dubuang (Feb 19, 2014)

Alright guys I did the RCA test and sure enough my sub doesn't pop when I unhook the rcas from the amp. When u turn off the ignition the sub does not pop with the RCAs off the amp. What can I do to fix this?


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## subterFUSE (Sep 21, 2009)

dubuang said:


> Alright guys I did the RCA test and sure enough my sub doesn't pop when I unhook the rcas from the amp. When u turn off the ignition the sub does not pop with the RCAs off the amp. What can I do to fix this?


Then it's definitely your DSP causing the pops.

How do you have the remote in of the DSP wired?
Is it connected to an ignition wire?


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## dubuang (Feb 19, 2014)

Ok so let me first tell u what I just did. So the audio control lc6i has a GTO feature meaning it senses speaker signals and can turn on the loc without a remote. So I basically disconnected my 12v remote from it and took out the remote out as well. I then wired the remote directly from my factory amp to my zapco 500m. 

Before I did this it didn't matter if the HU was off or on if I turned off the ignition the sub would pop.
Now, the sub only pops if the HU is on with the rewire I did. When the HU is off the sub doesn't pop. So I kinda fixed it a little but it's not fully fixed. 

My remote is from a wire I tapped in my factory amp, it receives 12v with ignition on and 0v with it off.

Any suggestions to what I can do so my sub won't pop when my HU is on?


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## ZombieHunter85 (Oct 30, 2012)

I had an alpine H/U with a bad (sub out rca) replaced the head unit and the pop went away. Thought it was the amp for the longest time.


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## dubuang (Feb 19, 2014)

Ok so I finally had someone else's help at my house. My brother came over and started and stopped the car for me and I was able to look and see if the sub was popping still. I'm glad I got this resolved the sub actually doesn't pop anymore with the rewiring I mentioned above. Head unit on or off it doesn't pop anymore. Thanks for all the suggestions and help guys, I'm glad there's many of you that chimed in, great forum to be on. I learned so much from this as well.


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## subterFUSE (Sep 21, 2009)

Cool. We just got my turn off pops solved, too. One of the remote wires was crossed.
Startup and shutdown are all silent now.


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## Kevinjones1978 (Mar 13, 2021)

dubuang said:


> Can you elaborate on why this would work being that the remote works just how it is set? Amp turns on and off when the 12v signal is on and off, so how would tapping into the source make a difference? I'm just wondering because I'm going to try a new ground spot at the moment and if it doesn't work I'll try what you suggested, but I don't see how it would change anything.


Your amp may be turned up to high. Turn it down to zero and compare the thump sound
as you adjust the gain knob


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