BUILT: Digital Factory Infotainment Integration Honda Civic Bose / Acura Integra ELS

[ashmostro]

5/4/26 Update
The following Honda and Acura models/years/trims are compatible with my digital integration device.

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Hi folks. i hail from the Integra Forums, owning a 2025 Integra Type S.

I wanted to let yall know that I have been working hard on hacking the factory signals and protocols to be able to install an aftermarket DSP amp wiring into the *digital* signal from the OEM head unit, as well as retaining the factory volume control. Today, I can say that I've accomplished this and I'm happy to share my findings with anyone who is interested in doing this on their FL5 (and probably other Hondas with premium sound).

The forum link above goes into a lot more detail, but the short of it is this, which I believe applies to Honda premium sound as well:

• The factory head unit sends a digital stereo signal to the outboard amplifier in the passenger kick panel, via S/PDIF using a JAE CE2 series connector which can be easily converted to an RCA form factor. This is purely for audio playback. My guess is that it's not DSP'ed, but I have not yet confirmed this.
• All other sounds like chimes, phone calls, navigation, etc are fed to the factory amp through independent analog channels. The factory amp knows to "duck" the digital S/PDIF signal when any of these are actively transmitting nonzero signal.
• The factory amp uses a traditional remote turn on lead
• The factory head unit can function when the amplifier is disconnected as long as you are using the proper termination resistances on digital signals like 75ohms for S/PDIF. This fools the head unit into thinking the factory amp is connected.
• Volume signal as well as tone controls are fed through a standard protocol RS485 signal from the head unit to the amplifier. I have decoded this signal to extract the volume signal from it, and built Arduino-based hardware that translates this signal into a varistor output via a digital potentiometer.

What does all this jibberish mean? it means we can have a true clean digital input into our DSP of choice while retaining factory volume controls, assuming the DSP you have selected uses an analog potentiometer for volume control (most do - I chose Arc Audio for its programmability).

I'm happy to elaborate and answer questions, so I'll leave this here for now to gather whoever might be interested first.

Best,
-Ash

 

[matttheazn]

Could you please provide any wiring diagrams you have found useful in this journey. I am currently looking to install a subwoofer and a custom 3 way and replacing the center speaker as well.

Current plan is to use a digital audio player direct into a helix dsp. Then use my phone for navigation and phone calls tapped from the factory system into the dsp.

Curious about your DAC conversion when going from spdif to rca. Thank you for all your hard work. I am sure I will have more questions in the coming weeks.

 

[ashmostro]

Happy to, and thanks for replying to my thread.

I think there's a good wiring diagram for the FL5 on this thread, and I refer you to it because it's a little different from the Integra connectors and pinouts, but the basic concept is the same, which is why I feel confident that my findings will apply to you all too.

Tell me more about exactly what your goals are, and I'm happy to talk through it here.

 

[ashmostro]

Curious about your DAC conversion when going from spdif to rca. Thank you for all your hard work. I am sure I will have more questions in the coming weeks.

The SPDIF signal is a standard protocol so there's nothing to convert other than the physical form factor of the cable termination. The factory uses a JAE CE2 coax connector, which I bought a receptacle for from Mouser, and then wired it into an RCA terminal (actually in my case, an RJ45 terminal because that's what my amp uses, but most amps are going to use RCA for a coax digital input).

 

[matttheazn]

My goals are having a clean digital signal all the way to the helix next v 8 ultimate and have the helix do the DAC with the highest quality possible.

I have a 12w7ae powered by a mosconi 1/10. I have not decided on 3 way speakers as of yet but leaning towards audiofrog. I may end up booking a day trip to the master tech expo in PHX in a couple of weeks of demo some speakers.

The installer that I am working with is in the process to become a helix dealer and is also a morel dealer, so there is different ways I'm looking at potential discounts and total system costs for custom 2 way pillar fab and a utility floor for when I take my back seats out for the sub.

My concern with high level tapping out of the bose amp is a sound quality issue for me. As much as I want OEM volume control and factory integration, I will always wonder would it sound better "x" way. So the plan is to do a DAP for music and phone for normal android auto stuff.

Does all your car alert sounds and navigation voice come from the center speaker as well?

Can you go into more detail the process of taking the spdif into rca?

I am traveling so I have not fully gone through your thread on the type s forums. Thank you so much for sharing here.

 

[matttheazn]

The SPDIF signal is a standard protocol so there's nothing to convert other than the physical form factor of the cable termination. The factory uses a JAE CE2 coax connector, which I bought a receptacle for from Mouser, and then wired it into an RCA terminal (actually in my case, an RJ45 terminal because that's what my amp uses, but most amps are going to use RCA for a coax digital input).

Got it. Spdif to coaxial

 

[ashmostro]

My goals are having a clean digital signal all the way to the helix next v 8 ultimate and have the helix do the DAC with the highest quality possible.

I have a 12w7ae powered by a mosconi 1/10. I have not decided on 3 way speakers as of yet but leaning towards audiofrog. I may end up booking a day trip to the master tech expo in PHX in a couple of weeks of demo some speakers.

The installer that I am working with is in the process to become a helix dealer and is also a morel dealer, so there is different ways I'm looking at potential discounts and total system costs for custom 2 way pillar fab and a utility floor for when I take my back seats out for the sub.

My concern with high level tapping out of the bose amp is a sound quality issue for me. As much as I want OEM volume control and factory integration, I will always wonder would it sound better "x" way. So the plan is to do a DAP for music and phone for normal android auto stuff.

Does all your car alert sounds and navigation voice come from the center speaker as well?

Can you go into more detail the process of taking the spdif into rca?

I am traveling so I have not fully gone through your thread on the type s forums. Thank you so much for sharing here.

That's helpful context. Sounds like your needs are pretty much the same as mine. Best possible source signal, the least possible re-processing, while retaining all factory features and controls.

A DAP will work fine (will be excellent sonically) and you will be able to use an external volume control that your DSP provides/sells. There's nothing wrong with that path and it's definitely the easiest path to excellent sound.

But, if you want to be able to have full factory integration and retain all chimes, nav sounds, phone calls, etc. along with retaining steering wheel controls, your only option up till now was to tap into the speaker level outs and reconstruct a flat signal in your DSP which means multiple D-A-D-A conversions which introduces noise, distortion, and phase variance across the passband.

If you go my route, you can get the same effective sound quality as a DAP by using USB audio on the factory radio. I'm assuming the FL5 offers that because the ITS does. Correct me if I'm wrong. Android Auto is also very good, but theoretically not as good as a DAP or USB audio as it has some rolloff above ~14kHz. But it's still going to sound a lot better than doing speaker level conversion. Personally, I will be using Android Auto 90% of the time, and USB for critical listening only. I rarely sit in my driveway and listen to music in the car... I'm always driving. So AA will be indistinguishable to DAP or USB for my ears.

 

[matttheazn]

My installer and I will be doing a deep dive in the type s post. I assume all relevant info is over there? Thank you again for your hard work and sharing. It is greatly appreciated.

 

[ashmostro]

My installer and I will be doing a deep dive in the type s post. I assume all relevant info is over there? Thank you again for your hard work and sharing. It is greatly appreciated.

Yeah a lot of it is there but maybe not every single technical detail. Your installer is welcome to reach out to me directly if s/he wants. I'm all about paying it forward.

 

[ashmostro]

Just so you're aware, the most complicated part of all of this is the volume control device. That's likely where your installer will need some help. It's a very custom device, with custom-programming involved. It's not hugely expensive in terms of parts, but it's definitely not for the faint of heart.

 

[matttheazn]

I definitely will in the coming weeks thank you.

 

[matttheazn]

Just so you're aware, the most complicated part of all of this is the volume control device. That's likely where your installer will need some help. It's a very custom device, with custom-programming involved. It's not hugely expensive in terms of parts, but it's definitely not for the faint of heart.

I have spare Arduino boards sitting on my desk. I will need to read through the post on my computer to get a better grasp of everything. Should not be too much issue. The installer and I are working together. When I say installer it is mostly the access to the tools and space for fabrication. They also have the fully resonix line that I will be using.

I ended up with a deal on a brand new w7 I could not pass up and now here I am figuring out how to put in it the civic and not worry about getting a high output alternator. 500 hours of researching how car audio all works together with OEM integration. You have done what no one else has done yet. Apparently maestro is coming soon through as well.

 

[ashmostro]

That W7 sure is going to improve your Civic's F/R weight distribution!

That's cool to hear about your comfort with microprocessor programming. The parts you will need are listed on this post.

 

[ashmostro]

I ended up with a deal on a brand new w7 I could not pass up and now here I am figuring out how to put in it the civic and not worry about getting a high output alternator. 500 hours of researching how car audio all works together with OEM integration. You have done what no one else has done yet. Apparently maestro is coming soon through as well.

You won't need a high output alternator if you are smart with your sub amplifier selection. Definitely go Class D or G to keep the current draw as low as possible (they are ridiculously more efficient than Class AB). Which size W7 did you get?

Oops I see you already told me which sub and amp you have. The Mosconi shouldn't require an HO alternator.

 

[coolnick]

Nice, I went down the rabbit hole looking for some of this over the summer but didn't really get anywhere. I might have to resurrect my interest now that you've done the heavy lifting. Thank you for sharing!

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