Wiring guide for NON B&O premium audio systems. No LOC required.

StangTime

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There's a lot of info scattered around the forums. Some correct, some not. The biggest mistake I see people making is trying to use a line output converter (LOC) to add an aftermarket system. They aren't required, add expense, and raise the noise floor. If you use the right signal source for your system and do some careful wiring, a LOC is not required. If only adding a sub to your existing factory stereo, that is the only case where you will use a LOC. Not covered in this post. Lot's of info on that elsewhere. This doesn't cover B&O systems. The wiring for these is different and I do not have info on that.


First step: Flatten the output of the head unit so that there is no funky molestation of the audio signal. We want a nice clean unaltered signal to feed our system with.
Use Forscan for this. If you don't know how, use the search function. Plenty of info on it here already.
There is one code to change in module 727 (Note: This code has been confirmed to work for 2021 models. If someone has different results please let me know):

727-01-02 00xx - First two digits we want set to 0. This disables any EQ Processing, bass roll-off etc. (tone controls will still function as normal)

Wiring it up: Study the diagrams. Everything you need is here.
Signals from the head unit are 2.7V RMS at maximum volume on the dial. Ford did us one good thing on the head units, they give us unclipped signal all the way to max. So you can use the whole volume knob range if you want.

If your goal is to remove the factory amp I recommend the idatalink HRN-AR-FO3 harness, it has all the necessary plugs needed to interface with the car without cutting the original factory wiring. This will have you completely unplug the factory amp from the car (you can even remove it to reduce weight). On that note, the warning chimes, door open, back-up warning, low fuel warning, ding-dongs etc. will now be re-directed to the speaker inside the gauge cluster because the Can-Bus is no longer connected to the factory amp. This is perfectly acceptable and doesn't impair the function of Sync or voice navigation as those sounds will still play through the new stereo system.

In the first diagram, ACM is the head unit and DSP module is the factory amplifier.
"CHIMES" should be replaced with the word "REAR" on pins 1,2,5,6 of C2385A. (typo in the service manual).
Pins 3,4,7,8 on C2385A are the FRONT audio signals
Pins 1,2,5,6 are REAR audio signals. All are low-level 2.7V RMS.
Ignore the noise cancellation signal lines, we won't use them.

IMPORTANT: If you are going to run the signals to the back of the car use the drivers side and make sure they are twisted pair and shielded for noise immunity. The outputs of the head unit are balanced for noise immunity but still require shielding.
ACM to APIM connections.png


Once you have your signals going into your aftermarket amplifier or DSP, it's up to you how you handle routing of the signals to power the # of channels (speakers) that your install requires. I couldn't possible cover all the options here.

Run all your speaker wire outputs from your amplifier up the drivers side of the car to the grey (C2385B) and brown (C2385C) connectors. Regular speaker wire "zip-cord" or Metra 9 conductor speaker cable work well for this. Make sure you run enough wires for all speakers.
The door midrange and the A-pillar tweeters are wired in parallel at some point under the dash. Best way to handle this is to use the brown C2385C factory connector for the door midrange and run new wires for your tweeters to your amplifier.

Getting it on: Note that the "Audio enable" from the ACM is only 6V. Many aftermarket amps have problems turning on with anything less than 7V. (Thanks Ford!) You will need a PAC TR4 to provide 12V from the 6V enable line, or tap into the BLUE/WHT wire in the trunk lid harness. That wire provides 12V to the rear camera circuit when the car is in ACC or RUN mode and that can be used to turn on your aftermarket system.

Mustang 9 speaker wiring.PNG

EDIT: Corrected tweeter wire colors.

Simplified diagram of the audio system. "AUDIO AMPLIFIER" is the factory amp/dsp unit.
9 Speaker Wiring.png


Hopefully this info will help out anyone looking at upgrading the system in their car.

12 speaker system would already have a sub woofer in the trunk. The info in this post should still apply if planning on replacing the OEM sub with an aftermarket version. I.E. replacing the sub driver, and bypassing the amp on the back of the subwoofer enclosure.

 
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Mike Pfeifer

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Thanks for the write up. This is good info, and you are right that info is all over the place, fragmented, incomplete, and at times incorrect. Unfortunately, I think I have to go down this road as well and I have a lot to think about in doing so. I really didn’t want to get that involved with an audio system upgrade like I used to do back in the day.
 
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Thanks for the write up. This is good info, and you are right that info is all over the place, fragmented, incomplete, and at times incorrect. Unfortunately, I think I have to go down this road as well and I have a lot to think about in doing so. I really didn’t want to get that involved with an audio system upgrade like I used to do back in the day.
Glad you found it useful. The audio system in these cars can be done in two steps. The first upgrade would be replace the door speakers, unplug the dash speaker and Forscan the head unit. Then be done with it. The next step is a doozy, akin to jumping off a cliff where you have to replace everything after the head unit.
 

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If there was an Pac-Audio AmpPro you could upgrade the speakers and amps in stages. :(
 

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Really nice of you to condense the scattered info for us. I've been collecting all the parts for a stealthbox install I want to do. I have been in these forums for months trying to understand it all. Unfortunately, I'm no good in wiring whatsoever so the harness stuff is confusing me... The harness you suggested requires buying an expensive DSP right? Is there another way around this part you could point me towards? What if you just replaced the 9 speaker factory amp with the 12 speaker one which already has a sub out. That seems cheaper but I'm no expert at all, This is very helpful but I might just have it professionally installed
 


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Really nice of you to condense the scattered info for us. I've been collecting all the parts for a stealthbox install I want to do. I have been in these forums for months trying to understand it all. Unfortunately, I'm no good in wiring whatsoever so the harness stuff is confusing me... The harness you suggested requires buying an expensive DSP right? Is there another way around this part you could point me towards? What if you just replaced the 9 speaker factory amp with the 12 speaker one which already has a sub out. That seems cheaper but I'm no expert at all, This is very helpful but I might just have it professionally installed
You can certainly do this without a DSP. You just run the signal lines from the HRN-AR-FO3 harness into your new aftermarket amp (must have built in active crossovers without a DSP). I wouldn't bother trying to swap up to a 12 channel OEM amp it really won't provide any benefit other than giving you subwoofer signals, then you still need a subwoofer amp and subwoofer. Might as well go with an after market system at that point. I used a 5 channel amp in my car (no rear speakers). 4 channels for the front plus a powerful subwoofer channel.

Here is an example of how you can connect the HRN-AR-FO3 to a Cat5e or Cat6e STP cable and subsequent audio equipment in the trunk:

View attachment Audio Signal Wiring Black AFO3.pdf
 
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The PDF here is a system diagram using the HRN-AR-FO3 harness connected to a Hertz H8 DSP and Hertz HCP 5D 5 channel amp with subwoofer.

The screw terminal blocks on the ends of the Cat6e cable are DVR ethernet connectors. Then all you need is a shielded network cable run between them for you signal run.
Link: DVR Ethernet Screw Terminals
Link: Cat6 STP cable
The use wire ferrules on the screw terminals is recommended for a solid connection.

View attachment Audio System Wiring Jul12-2021.pdf
 

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Okay the wiring is starting to make a lot more sense to me thank you for that you cleared a good deal up for me so far. If you don't mind I did have a follow up question or 2. I actually have a JL--RD500/1 amp with crossovers(solely to run a subwoofer) I want to install to a 9 speaker system + the sub. I was told get the 12 speaker amp so I could have all the other signals + subwoofer and substitute in my signal there, I think.. I just want to be sure I get the right harness for what I'm doing. I'm fine with audio quality and volume on the 9 speaker I just need some bass + I'd like to control volume from head unit.
So if I got the FO3 harness & Cat5 I would have what I need?
I really appreciate the help so far.
 
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Okay the wiring is starting to make a lot more sense to me thank you for that you cleared a good deal up for me so far. If you don't mind I did have a follow up question or 2. I actually have a JL--RD500/1 amp with crossovers(solely to run a subwoofer) I want to install to a 9 speaker system + the sub. I was told get the 12 speaker amp so I could have all the other signals + subwoofer and substitute in my signal there, I think.. I just want to be sure I get the right harness for what I'm doing. I'm fine with audio quality and volume on the 9 speaker I just need some bass + I'd like to control volume from head unit.
So if I got the FO3 harness & Cat5 I would have what I need?
I really appreciate the help so far.
If you are going to just add a subwoofer and subwoofer amp using the JL RD500/1 you have an even simpler without the need for any harness because that amp has speaker level inputs. Unplug the rear deck speakers and extend the wires to the sub amplifier input jacks with these: RCA to AV screw terminal adapters
Mount your amp in the spare tire well or other suitable place (under the rear deck even), run the 12v battery power and ground the amp at a solid point (bracket in the spare area is great for this), add a subwoofer box and as a final step so you get good sub bass to the amp inputs, use Forscan to flatten the EQ to restore bass on the rear channels.
 

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If you are going to just add a subwoofer and subwoofer amp using the JL RD500/1 you have an even simpler without the need for any harness because that amp has speaker level inputs. Unplug the rear deck speakers and extend the wires to the sub amplifier input jacks with these: RCA to AV screw terminal adapters
Mount your amp in the spare tire well or other suitable place (under the rear deck even), run the 12v battery power and ground the amp at a solid point (bracket in the spare area is great for this), add a subwoofer box and as a final step so you get good sub bass to the amp inputs, use Forscan to flatten the EQ to restore bass on the rear channels.
Wait it is really that easy? Let me be I am understanding correct and have everything I need.. I got the amp I talked about, 4 gauge power wire and a JL-Audio Stealthbox Subwoofer. The amp can read the signals from rear deck so I grab speaker level input from there, wire it to the sub, and it will get all the signals. The power will come from the battery running the amp, No harness.
If it is easiest that way why have a lot of people grabbed the signal pre amp with some make shift harness'? A I may decide to eventually begin replacing the rear deck or door speakers would doing it this way make any of that more difficult?
- Sorry about the rookie quesitons
 
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Wait it is really that easy? Let me be I am understanding correct and have everything I need.. I got the amp I talked about, 4 gauge power wire and a JL-Audio Stealthbox Subwoofer. The amp can read the signals from rear deck so I grab speaker level input from there, wire it to the sub, and it will get all the signals. The power will come from the battery running the amp, No harness.
If it is easiest that way why have a lot of people grabbed the signal pre amp with some make shift harness'? A I may decide to eventually begin replacing the rear deck or door speakers would doing it this way make any of that more difficult?
- Sorry about the rookie quesitons
You got it. Yes, it's really that easy to add a sub with an amp that has speaker level inputs. Your amp should be set to auto turn-on detecting the signal and switching on/off accordingly. No need for a remote turn-on wire.

The factory rear speakers could be replaced down the road if you like. But I wouldn't bother. Rear speakers just pull the sound to the back of the car. It doesn't sound good, the only advantage is it's slightly louder. Put your money into a better set of speakers for the doors and A-pillar tweeters, which can be upgraded at anytime.

Here is a great thread on installing just a subwoofer and amp. Skip the part about the LOC because you are going to wire the rear speaker lines to the input of your amp. (use twisted pair for noise suppression).
https://www.mustang6g.com/forums/th...at-install-long-post-heavy-pic-warning.78694/
 
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On that note, the warning chimes, door open, back-up warning, low fuel warning, ding-dongs etc. will now be re-directed to the speaker inside the gauge cluster because the Can-Bus is no longer connected to the factory amp. This is perfectly acceptable and doesn't impair the function of Sync or voice navigation as those sounds will still play through the new stereo system.
Can you describe this in a little more detail, as in which sounds will be lost to the cluster? I’m not clear on what sounds are generated at the amplifier and what sounds are generated in the head unit. Is it ONLY door chimes and the reverse sensor beeping? Does the door chime in the cluster retain the same sound or does it get replaced with a simple beep? Is there any other instance where a sound will now get rerouted to the cluster?
Honestly, this is the *one* thing holding me back from going fully aftermarket. I hate to lose *any* functionality, it’s all part of the charm and character of the car. I’ve been down this road before and wished I had made different choices. Just trying to avoid that this time. It all depends on how significant the changes will be.
 
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Can you describe this in a little more detail, as in which sounds will be lost to the cluster? I’m not clear on what sounds are generated at the amplifier and what sounds are generated in the head unit. Is it ONLY door chimes and the reverse sensor beeping? Does the door chime in the cluster retain the same sound or does it get replaced with a simple beep? Is there any other instance where a sound will now get rerouted to the cluster?
Honestly, this is the *one* thing holding me back from going fully aftermarket. I hate to lose *any* functionality, it’s all part of the charm and character of the car. I’ve been down this road before and wished I had made different choices. Just trying to avoid that this time. It all depends on how significant the changes will be.
All warning chimes get re-routed to the single low-fidelity speaker inside the gauges. The sounds are the same. Image listening to your favourite song on FM radio and then hearing the same song on AM radio. Basically the fidelity is reduced. You can test this out on your car very easily to see if you can live with the difference. Simply unplug the brown connector at the amp in the drivers kick panel. Or find the fuse for the amp and pull it. The car will detect the amp is missing and will force the warning chimes to play through the gauge cluster. Plug it back in when you're done testing.
There is a way to retain all normal functions but you will need to use the Meastro HRN-AR-FO3 and a Rockford DSR-1. Which has it's own set of problems for some people.
 

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Thanks, was thinking I could pull the power supply from the amp and see what happens as a test, but didn’t know if I needed to do something to switch the sounds over beyond that.
 

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Wait it is really that easy? Let me be I am understanding correct and have everything I need.. I got the amp I talked about, 4 gauge power wire and a JL-Audio Stealthbox Subwoofer. The amp can read the signals from rear deck so I grab speaker level input from there, wire it to the sub, and it will get all the signals. The power will come from the battery running the amp, No harness.
If it is easiest that way why have a lot of people grabbed the signal pre amp with some make shift harness'? A I may decide to eventually begin replacing the rear deck or door speakers would doing it this way make any of that more difficult?
- Sorry about the rookie quesitons
It is. Running the power wire cleanly is really the most difficult part. A few notes (from my '21 9 speaker LOC sub install).

1) I would use posi-taps next time. The speaker wires are very small and braided and getting a tap in there... well posi-taps is the best way and the cleanest.

2) I would use a remote turn on (in the bundle in the trunk) not the amp line level "audio sensing" as a remote turn on. I tried this on my Jetta and at various times the car will check the speakers sending a false on signal (when you unlock the car for instance) and I got a "thump" from the sub, so I would use the remote wire.
 

 
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