Aftermarket Stereo Issues

[GWraith]

I have a 2021 Mustang GT 5.0L Roushcharged base model. It came with the 4in sync 3 stereo.

I have upgraded the software on the APIM to 8" and added a touch screen and toggles.

That all works fine,

The issue I'm having is I added an aftermarket:
4-Channel AMP JBL Stadium 4
plugnplaykits.com 4 channel 17' harness
PRV DSP
10" Pioneer Loaded Sub Enclosure
5 FARAD cap
All 6 speaker replacements with PowerBass OEM

I originally set it up to use hi-line out but it had way too much noise on audio wires when the sound was off. I switched it over to lineout no EQ using Forscan and set my amp and DSP to it as well.

The noise stopped at +0 gain but only when I have left and right channels bonded for each output on the DSP.

My Pioneer-loaded sub enclosure had to be used through a Ground Loop Isolator or I'd get alternator whine really bad.

My wiring setup is straight ground and a positive 4 gauge to the battery on the passenger side. 3-way splitter terminal so everything is wired in parallel. The audio wires to the amp and from the amp are run on the driver's side. Originally I had the static issue as well when all of it was on the passenger side so I rerouted the speakers "out & in" to the driver side and the noise remained unchanged which is why I stopped using Hi-EQ output and changed to line level, the hiss was non-existent at 0 Gain.

Since I have a Roush supercharger the tune has disabled active battery charging so when the car is on its pushes 14.3V - 15V at all times. The alternator is 175amp stock.

The battery is in good health, stock battery, 12.7V

I have no power issue and the cap is simply there for voltage stability.

I have no static on my 2 channels out to the sub but I also have my LPF set at 145Hz.

On my DSP I had to combine FL/RL (A)and FR/RR(B) to bring the 4 channels into 2 (A & B). Then they break back out to 4 after the DSP. If those 4 channels are all A+B I get no static at 0 gain but the gain noise slowly increases as I add gain. The gain will also be present depending on the EQ preset selected.

HPF is set on all 4 channels at 80Hz.

If I set Each channel according to the side of the car eg. Channel 1 (A) 2(B) 3(A) 4(B) I immediately get static with no audio even at 0 gain.

I plan to have the system mic tuned for accuracy but I need to solve with white noise/hiss issue.

My thought is that the Audio Control Module (ACM) is the source of the hiss but being a 2021 I cant source a new one to compare. I have a 2017 ACM sitting in the garage but using that throws codes and I haven't tried swapping it in just to test the audio since I put the system in.

The system gets plenty loud at my max of 22/30 ticks. Should I continue to chase this white noise issue? Is there an increase in fidelity or quality if I separate the left and right channels?

Before I had the DSP the hiss/white noise was more prevalent on the front than the back speakers eg. 2% gain on the front before I heard it while 15% gain on the back before I heard it.

I have not found any recent posts about putting any extra grounds on the ACM, the last one I found was like 2010. Our radios from what I understand do have a small-cap connected to them to help with the noise as a reference from the parts catalog.

https://parts.ford.com/shop/en/us/e...ts/capacitor-assy-radio-suppression-6501243-1

A new ACM from Ford cost almost $1K and didn't have the issue when it was stock so I'm assuming they wouldn't warranty it anyway.

https://parts.ford.com/shop/SearchD...pe=&beginIndex=&pageSize=12&pageNumber=1#list

Let me know if yall have any experience with this or have any suggestions. Thanks for the help!

To reference the pictures the output from the amp is in between the cap and the amp while the input is toward the driverside wall. The PRC DSP was added to the third slot for power on the splitter. So the cap and the DSP are sharing a power port whing should not matter as they are still in parallel. I don't have pics with the DSP installed but image it under the amp. As the DSP didn't bring the problem in I doubt it's the cause.

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[Cathul]

The ACM in the Ford is known for having noise issues. My 2016 hase recognizable floor noise as well on higher volume and higher gains (which amplifies then the floor noise even further).
Except for going for an aftermarket radio there is nothing you can do about that.
If you had the B&O system to begin with one option would've been the PAC-Audio AmpPro with digital out, which, to my knowledge, doesn't have the noise floor as the variable line level from the ACM.

 

[GWraith]

The ACM in the Ford is known for having noise issues. My 2016 hase recognizable floor noise as well on higher volume and higher gains (which amplifies then the floor noise even further).
Except for going for an aftermarket radio there is nothing you can do about that.
If you had the B&O system to begin with one option would've been the PAC-Audio AmpPro with digital out, which, to my knowledge, doesn't have the noise floor as the variable line level from the ACM.

In your opinion would it be worth sourcing a B&O capable ACM or is that a totally separate module?

 

[StangTime]

I found the APIM on my 2019 to be very quiet actually. I am using a Cat5e STP cable harness that I made that runs off the APIM outputs to my balanced inputs on my DSP in the trunk. I am using the full volume control on the head unit to limit the amount of gain needed downstream for full output. I can turn the volume knob all the way to max where the amp just begins to barely clip.

I see your ground wires running all over the place in your install. Not sure what that is all about. It could be part of the problem.
Also unrelated to your noise issue, why do you have your sub LPF set to 145hz? That shouldn't be any higher than 80 to 100hz max.

This is how I wired my APIM to my system: https://www.mustang6g.com/forums/th...aker-system-without-a-loc.159271/post-3244386

A DIY harness: Signal Wiring from APIM to RCA plugs

My complete system diagram: 5 Channel System wiring with DSP
I am not using a bulk capacitor. IMO they are not necessary for a system of this size with good wiring.

 

[GWraith]

I found the APIM on my 2019 to be very quiet actually. I am using a Cat5e STP cable harness that I made that runs off the APIM outputs to my balanced inputs on my DSP in the trunk. I am using the full volume control on the head unit to limit the amount of gain needed downstream for full output. I can turn the volume knob all the way to max where the amp just begins to barely clip.

I see your ground wires running all over the place in your install. Not sure what that is all about. It could be part of the problem.
Also unrelated to your noise issue, why do you have your sub LPF set to 145hz? That shouldn't be any higher than 80 to 100hz max.

This is how I wired my APIM to my system: https://www.mustang6g.com/forums/th...aker-system-without-a-loc.159271/post-3244386

A DIY harness: Signal Wiring from APIM to RCA plugs

My complete system diagram: 5 Channel System wiring with DSP
I am not using a bulk capacitor. IMO they are not necessary for a system of this size with good wiring.

Thanks for the reply. However, the APIM has the head unit software and Sync it does not route or send musical audio. ACM is what you are referring to. The power wires are - / + 4 gauge to the back of the car and -/+ 8 gauge to each device, Amp, Cap, Sub, and 16 Gauge + / - to the DSP. The power wires are in no way the problem.

Either the noise is being induced on the harness or it is coming out of the head unit directly.

I'm still tweaking the LPF but my sub can hit 30Hz to 125Hz and since I listen to rock music I keep it high. I will adjust it back down to 125Hz as I must have been thinking about somthing else when I set it.

IF the head unit is the cause do you guys know of any way to remove the noise? Extra head unit ground, ground loop isolator, ect?

I am warry of putting a ground loop isolator on my primary RCAs in because of the sound quality degradation and lower frequency attenuation.

I know switching to another head would probably fix the issue but I don't want to change from stock. Just trying to get an idea if my component is bad or this is a normal thing for these ACMs.

My T harness is twisted pairs but I don't think the harness itself is shielded. I could add a shield but I'd have to pull the whole harness out and repin the connector.

Also, the base models don't have a DSP.

Here are pics of the harness before it went in. As you can see there may be a shield wire inside of it connected at the head unit end but no evidence of it at the other end. SO either it's not shielded or they are using a floating shield.

Also, you said the output from the ACM is balanced. Maybe that's why I get more noise when I separate left and right audio in my DSP. Just a guess there.

Should I be bonding my 4 channels into 2 for my DSP or just using the rear channels to supply audio?

 

[Cathul]

After all the noise can originate from different sources. It may be the ACM, the wire, the amp.
Typically floor noise origins from the active components like headunit, amps and the gain structure.
Does the noise dissappear when you disconnect the RCAs from the amp?
If not chances are high that it is the amp.
Floor noise from the active components cannot be altered with different wiring.

 

[StangTime]

Thanks for the reply. However, the APIM has the head unit software and Sync it does not route or send musical audio. ACM is what you are referring to. The power wires are - / + 4 gauge to the back of the car and -/+ 8 gauge to each device, Amp, Cap, Sub, and 16 Gauge + / - to the DSP. The power wires are in no way the problem.

Either the noise is being induced on the harness or it is coming out of the head unit directly.

I'm still tweaking the LPF but my sub can hit 30Hz to 125Hz and since I listen to rock music I keep it high. I will adjust it back down to 125Hz as I must have been thinking about somthing else when I set it.

IF the head unit is the cause do you guys know of any way to remove the noise? Extra head unit ground, ground loop isolator, ect?

I warry of putting a ground loop isolator on my primary RCAs in because of the sound quality degradation and lower frequency attenuation.

I know switching to another head would probably fix the issue but I don't want to change from stock. Just trying to get an idea if my component is bad or this is a normal thing for these ACMs.

My T harness is twisted pairs but I don't think the harness itself is shielded. I could add a shield but I'd have to pull the whole harness out and repin the connector.

Also, the base models don't have a DSP.

Oh yes, you are correct. I always get the acronyms mixed up. ACM is what I am talking about.

"The power wires are in no way the problem."
They may not be the source of the noise but you have it connected in a way that defeats the purpose of having that cap installed.

You've got more than 18" of +wire and haven't connected the amp + to the capacitor as far as I can tell. Looks like it's going all the way back to the distribution block. Grounding could be optimized better.
FWIW my amp ground is about a foot long before it is bolted to the chassis with toothed star-washers. My DSP is grounded at the same point.

On your head unit volume control, what number does your system start to clip? Maybe your gains are set way too high?

Disconnect the sub and the capacitor power. Disconnect the sub RCA connections. Ground the amp directly to the car chassis. Start with the basics and trouble shoot from there.

 

[GWraith]

I see what you're saying but the cap will still function the same in parallel. The cap is the closest most abundant power source. The two amps will pull mostly from it and in turn the battery. Capacitors do not improve or increase how much power your car with stands that is always dependent on the alternator. The cap functions to smooth out voltage fluctuations when a large draw happens protecting the battery and alternator from direct draw. Any audio installer will tell you a direct ground to the battery is the best ground. All amps, DSP, and caps are grounded to the same point. I originally had the cap in series with the amps but the issue was still present. That's why I went nuclear and ran larger cables direct from the battery. I think I'm going to add an extra ground to the chassis of the ACM and see if it improves. Then I might try the 2017 premium ACM to see what happens. I already know the 2017 ACM does not have the power ability my 2021 basic ACM does as when I put it in before it was way quieter on the volume capabilities.

 

[GWraith]

After all the noise can originate from different sources. It may be the ACM, the wire, the amp.
Typically floor noise origins from the active components like headunit, amps and the gain structure.
Does the noise dissappear when you disconnect the RCAs from the amp?
If not chances are high that it is the amp.
Floor noise from the active components cannot be altered with different wiring.

Yes it does disappear when unplugged from the amp. That's why I'm going to look into the wires or try and source a new ACM to check.

 

[GWraith]

Ok, so the problem is a bit different now. I have slight static being generated by the DSP but it can only be heard at volume 0 and within an inch of the speaker.

I'm going to get a power filter for the DSP and see if I can clear that up.

I also found out that the rear channels don't produce audio in line-out no EQ mode.

I checked the front channels.

Front Left 32 mV @ volume 5 / 30 - 16 mV with stereo off.
Front Right 55 mV @ Volume 5 / 30 - 20 mV with stereo off.

I'm not sure if that's EMI keeping it so unbalanced or the ACM is just inherently unbalanced?

Rear Left 15 mV with the stereo off or on.
Rear Right 9 mV with the stereo off or on.

This is probably the inherent problem with the stock ACM it uses a VERY low signal voltage so it's easy for any EMI to influence the line.

The system sounds fine overall and I'm hoping the power filter on the PRV DSP clears up what hiss is left so I can give it a bit of gain and adjust the EQ without increasing the overall hiss.


After some more research:

Using the below table I actually adjusted my ACM for 727-01-01 xx70 xxxx xxxx. That sets only the front channels as variable line-level 1-4v, shuts rear off, and turns off all AUX channels since I'm not using them anyway. Everything I found before said to make it xx5A but I'm not using AUX channels and the rears are redundant since I only need a left and right input. Also as stated above the rears werent even working on that option anyways.

I also still left 727-01-02 as x0xx xxxx xxxx for no EQ processing in the ACM.

I will retest the voltages again tomorrow to see what it looks like and if this cleans up the signal and balance.

I got these charts from the 2018+ ACM Forscan sheets. There is a 2021 F150 sheet out there that has way differnt things but I think thats only for premium systems.

 

[GWraith]

The power filter didn't get rid of the hiss from the DSP. Was a long shot anyways. Emailing PRV to see if this is normal or needs replaced.

Voltages are the same as before at volume 5.

I'm gonna mess with the master volume on the DSP and then correct it with gain from the amps and see if I can tamp it down. I'm also going to do a rewire of the RCAs I'm going to go down to only 2 outputs for the 4 channel. Left out then split to front and rear left, and then right out split the same way. Then I can control back to front fade with the 4 channel amp and left to right balance with the DSP.

 

[GWraith]

Everything is solid now. The redid the RCA with single left/right output then split each left and right to the front/rear left and front/rear right respectively. I also lowered the gain on the output of the DSP by -7db to eliminate the hiss and moved master volume to 95%. I then used the gain on the 4 channel amp to volume match the stereo. I did not pull db from the sub output as the his was being produced in the higher frequency so the sub was never affected. I still plan to get the DSP professionally configured for accurate sound production but for now it sounds great. I think when I do that I might have them build me an amp rack or reconfigure the setup to hide wires and make it look cleaner. Thanks for the assist ya'll or at least reading about the journey

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