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

[ashmostro]

Wiring Diagrams as requested!
I included the "before" along with the "after"

Keen eyes may have noticed that I decided last night to make this a totally plug-and-play affair, integrating the factory power source originally for the factory amplifier, to now power the Integrator Device. Since this travels on the same OE harness that also feeds the amplified signal to the speakers, this frees things up to build a custom T-harness between the Integrator Device, Aftermarket DSP/Amp, and the factory speaker wiring, making everything plug-and-play (you just need to provide power and ground for the DSP amplifier, as well as supply your own RCA digital cable of appropriate length for your chosen DSP install location).

This also means that the factory amplifier can be fully removed from the car, and the Integrator Device can be installed in its location in the passenger kick panel.

 

[ashmostro]

BTW this is going to require a full redesign of the PCB, and the enclosure will need to be larger overall. But I think that's a small price to pay for the integration, and since it can now be installed in place of the factory amp thanks to the T-harness, I don't think the additional size will matter (and it will still be smaller than the OE amplifier anyway).

 

[AspecR]

Major Update 3/21/26

I am adding two features to the device to make it more broadly useable. Well, technically, one feature and one option.

1. Most modern DSPs use a 3.3V architecture for their accessory remote volume controls, while older ones may use 5V (even some newer lower-end brands can use 5V). I built this device to be compatible with 3.3V because that's what my DSP uses. I've migrated to a new architecture that allows you to switch between 3.3V and 5V depending on your application, via firmware update. I'll be building Windows software to go along with this device that you or your installer can run to make easy compatibility adjustments.
2. I had the thought of doubling up the DAC control submodule from one DAC to two DACs as an option. Why? For subwoofer level control! If you want the optional feature, you can tie in your bass EQ setting on your head unit into your DSP's subwoofer level control, if it has the additional capability. That, or if you use a separate amp for your subwoofer(s) and it comes with its own level remote, you can tie this second output into that. This would interface with the car in exactly the same way as the Single-DAC model, just with one extra output wire for your sub.

I'm quite curious to hear how interested folks will be in Item 2 above. I'm leaning towards offering this as an option rather than one SKU, because A) not everyone wants a subwoofer level control and B) it's more complex and therefore costs more to implement.

I'm starting to think this device might be more of an installer-focused device than a consumer-level one, because it will take a slightly deeper than typical understanding of wiring and configuration to make this work in your particular system. I'm curious about that, too - would you DIY this into your system, or rely on an installer to do it for you?

I think offering option 2 as an additional component makes sense. With the right instructions or youtube videos, I'm sure most will not be oppsed to doing the installs themselves. I know I would

 

[AspecR]

BTW this is going to require a full redesign of the PCB, and the enclosure will need to be larger overall. But I think that's a small price to pay for the integration, and since it can now be installed in place of the factory amp thanks to the T-harness, I don't think the additional size will matter (and it will still be smaller than the OE amplifier anyway).

If possible you should maybe also post a list of recommended amps or DSPs for DIYers to consider like something from Helix, Audiocontrol or the Arc Audio PSM Pro which is the DSP I'm considering.

 

[ashmostro]

I'm actually working on that too... requires some R&D and volunteers with various models and brands of DSP, and models of Civic/other Hondas.

I'm a one man shop with a day job so this is my best speed. I wish I could go faster!

 

[AspecR]

I'm actually working on that too... requires some R&D and volunteers with various models and brands of DSP, and models of Civic/other Hondas.

I'm a one man shop with a day job so this is my best speed. I wish I could go faster!

Take your time, we appreciate all the effort you've put in thus far.

 

[ashmostro]

If possible you should maybe also post a list of recommended amps or DSPs for DIYers to consider like something from Helix, Audiocontrol or the Arc Audio PSM Pro which is the DSP I'm considering.

BTW I know for sure this will work on Arc Audio amps that use the LRC-# remotes (since that's what I have).

I'm fairly certain that Helix amps that use the URC-# remotes will also work, as they use plain potentiometers for volume control strategy as well.

 

[jtlctr]

@ashmostro you are a legend! Very, very nice work!

 

[ashmostro]

Thank you good sir!

 

[ashmostro]

Accomplished some insane shi this weekend! This thing is becoming a true automotive grade, drop in device!

Details to come tonight.

 

[jtlctr]

I pulled my car out of storage today. As I was driving home, I was testing different types of music to see how it sounded. It’s pretty lame! You were in my thoughts!

 

[ashmostro]

It won't be too long now! I'm estimating a shippable beta testing (but fully functional) product in about a month!

 

[ashmostro]

Ok folks, I spent probably 24 full hours this weekend working on an idea I had on Friday night (I couldn't sleep the whole night because of it).

Here's a sort of list of evolutions that have happened, in order, which should hopefully give some context to the progression:

1. I moved away from using an Arduino microcontroller, to instead building my own microprocessor network. Reasons for this change were: automotive-grade reliability, as the Arduino isn't designed to operate permanently in an automotive environment, which sees wild temperature and humidity ranges that a "home" device isn't designed for. Moving to "bare metal" allowed me to pick high temperature range components all the way down to resistors and capacitors. The second thing I'll be able to do in the name of reliability is to apply a conformal coating to the whole device, which is another automotive manufacturer-grade manufacturing step that prevents corrosion over time, as it creates a hermetic seal over every surface. The final reason to do this is to get back some board real estate, which I knew I was going to need for the next idea I had...
2. ...which was to bring onboard the entire "T" harness assembly into the device. I won't bore you with the details, and just say this took the most time to do. This strategic change makes the device truly drop-in. On one side of the device you will have the three exact same connectors that your factory amplifier has, arranged in the exact same order and orientation. On the opposite end of the device you'll have the SPDIF output, and a custom harness that I'll supply, which contains all of the cabling to run to your DSP, all in one bundle. Speaker wires, remote turn on, and the volume control all in one neat package. You're just running that one harness and a digital coaxial cable to your DSP amp. That's it.
3. Finally, in order to enable (2) and not have a massive footprint, I realized I needed to split the platform into a motherboard and daughterboard, which would sandwich on top of each other in a clamshell enclosure (see below for a manufacturer photo of the exact enclosure I will use). There will be a simple internal bridge connector between the two boards for them to talk to each other. There's a hidden benefit to this change that might actually be the most powerful of all so far: The motherboard contains all the logic for the volume control while the daughterboard houses all the power, I/O and passthrough signals, and consequently all the vehicle harness connectors too. Why does this matter? Well, I've learned that current gen Honda/Acuras do not all share the same pinouts across models. Even the Civic with Bose is slightly different from my Acura with ELS. So, to add new cars, I only need to develop a new daughterboard, which is much less complex than rearranging the logic circuitry just because the I/O has changed.

The first two models I will build are for the Acura Integra ELS system, and the Civic Bose system. Once those are successfully beta tested by early adopters (ahem), I will purchase the service manuals for all other current Honda products to see what needs to be changed on the daughterboard to support additional models.

Oh, and by the way, the dimensions of the enclosure are 4" x 4.75" x 1.85", and the end caps have integrated mounting tabs for surface mounting if you like. I anticipate this unit will simply replace the factory amp, which is much larger than this is, so it can probably be secured into place inside the kick panel with zip ties, but the tabs are available to anyone who prefers to fabricate a custom bracket for a pro-level install.

Let me know any questions you may have. Talking through stuff gives me more to think about and helps me catch issues I hadn't considered. I appreciate your enthusiasm about this project! It's a ton of work but it's also extremely satisfying and fun.

Now for some pics - the enclosure, and the daughterboard. For the daughterboard, one of the OEM amp's connectors is so new that the manufacturer has not yet released a 3D step file for it, so it is missing from the 3D render pasted below. I've emailed them asking if they can send one - we'll see!

 

[Zavage]

It's super interesting.
From experiences of the 10th gen, please check, that the signal delay should be as little as possible as hands free telephone might have a issue.
There is for the 10th gen a similar Metra Kit available, but it's not 100% perfectly usable as somehow you will get a huge delay for the hft system and it echo's too much.

 

[ashmostro]

It's super interesting.
From experiences of the 10th gen, please check, that the signal delay should be as little as possible as hands free telephone might have a issue.
There is for the 10th gen a similar Metra Kit available, but it's not 100% perfectly usable as somehow you will get a huge delay for the hft system and it echo's too much.

If I were to guess (and I am) that sounds more like an ANC (noise cancellation) issue. On aftermarket systems ANC should be excluded as the DSP doesn't know what to do with the additional signal. My device leaves those pins floating for this reason.

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