Sound system build progress thread (warning: will be slooooow)

[ashmostro]

Oh, and I scrapped the plan of running the sub off of the DSP amp (would be 250W into 4 ohms) and instead bought a 700W@1 ohm amp for max headroom. The sub I bought can be wired for 4 or 1 ohm thanks to its 2 ohm DV coils.

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[ashmostro]

Folks, I have some pretty cool news (I think it's cool, at least)!

I have sleuthed ALL of the connectors to and from the factory ELS amplifier, which means I can build T harnesses for myself and anyone who wants to go full factory integration with a DSP system (ie, not just the subwoofer, but all outputs).

I've ordered what I think are the right connectors from Mouser, and if I confirm that they are in fact the right ones, I'll post back up here.

No one, literally no one I've contacted in the industry knew what the output connector is for this amplifier, let alone where to source it. I've spent months searching for it, and found it "accidentally" today. I'm buzzing with excitement!

I've also figured out exactly what type of connector the factory uses for the digital input signal to the amp, so we will have options for the more typical, easier, but lower fidelity speaker-level A/D/A DSP conversion method, or the higher fidelity but more complex and less common OE amplifier bypass/direct digital input to DSP which is the approach I'm going to try to make work first.

But, either way, you need a way to feed the aftermarket amp's speaker outputs into the factory speaker wiring so you don't have to run all new wires into the doors. This is where the T-harness I speak of above comes in, and why it's so exciting for this platform. It allows us to do all this in a factory reversible manner (no cutting of factory wiring).

Stay tuned...

 

[ashmostro]

Progress is being made! I have started building the custom connector to inject signal to the factory speaker wiring harness. Tomorrow, I'll start on the input side. Next will be the proprietary volume signal converter, then power wiring for the amps, mounting the amps, then the speakers and sound deadening.

 

[ashmostro]

I'm curious - who here would be interested in a complete T harness for full system integration (specifically analog speaker level input, not pure digital conversion like I'm doing)? This harness would enable intercepting every independent OEM channel into your DSP/amplifier.

Building the harness is a pretty involved procedure since the output plug on the ELS amplifier is so new that there is only a board-mount connector available, rather than the much easier to assemble cable-style plug.

 

[ABPDE5]

I'd be interested in breaking the sub out from the rest.

 

[ashmostro]

I'd be interested in breaking the sub out from the rest.

That would be quite easy actually. But I'm curious - why, when you can just intercept the signal at the sub in the trunk? What's your design goal?

 

[ABPDE5]

That would be quite easy actually. But I'm curious - why, when you can just intercept the signal at the sub in the trunk? What's your design goal?

Line level vs speaker level. I'm not sure it would be worth the effort, just curious.

 

[ashmostro]

Line level vs speaker level. I'm not sure it would be worth the effort, just curious.

Ah, sorry I wasn't clear at all. Tapping into the signal at the amp or the sub is the same thing. They are all speaker level outputs. The factory system has no line level inputs, just a single stereo digital input that the amp converts to analog and then amplifies after processing it.

The t harness I'm proposing would be to intercept every single speaker output signal so you can use a DSP to reconstruct the original signal with summing and eq. This is the most common factory integration approach. But as you suggest, it's not the highest fidelity solution which is why I'm going full digital.

For your sub-only use case it would be unnecessary complexity and wouldn't change the sound quality at all vs tapping in at the sub since it's electrically identical.

 

[ABPDE5]

Ah, sorry I wasn't clear at all. Tapping into the signal at the amp or the sub is the same thing. They are all speaker level outputs. The factory system has no line level inputs, just a single stereo digital input that the amp converts to analog and then amplifies after processing it.

The t harness I'm proposing would be to intercept every single speaker output signal so you can use a DSP to reconstruct the original signal with assuming and eq. This is the most common factory integration approach. But as you suggest, it's not the highest fidelity solution which is why I'm going full digital.

For your sub-only use case it would be unnecessary complexity and wouldn't change the sound quality at all vs tapping in at the sub since it's electrically identical.

That's what I would have expected. I misinterpreted your explanation of the connector... wishful thinking

 

[ashmostro]

I see where I wrote line level instead of speaker level and fixed it

 

[ashmostro]

Accomplished a lot today. My goal was to decode as much of the factory head unit and amplifier "signals" as possible. Things I wanted to understand:

1. Is system volume command carried on the RS485 signal? Answer: YES
2. What are the extents of the HEX code for volume:
   • Min (= 0) on HU = 0xFE hex (= 94) on RS485 signal
   • Max (= 40) on HU = 0x5E hex (= 254) on RS485 signal
   • 40 steps on HU = 4 steps on hex code, so very easy math to set up the digipot
3. Can the factory head unit function without the factory amplifier connected? Answer: YES-ish...
   • The factory HU did not seem to like the SPDIF connection being severed as some functions stopped working when I did (but not all).
   • I found that if I plugged the SPDIF back in but kept all other amp harnesses unplugged (ie no power to the factory amp) the head unit was happy again.
   • This implies that the SPDIF is not bidirectional and the HU is only looking for a load across that terminal to be happy. This is very good news.
4. Are beeps/navi/parking sensor chimes, etc analog signals that I can feed into my DSP amp?
   • Yes. They do not appear to be proprietary digital signals which means they can be fed into a DSP amp with signal ducking enabled, which mutes/suppresses the music signal whenever it sees signal on any of these inputs.
   • This will preserve the factory auxiliary sounds like phone calls, beeps, etc.
5. Does the factory microphone still work without the amplifier connected and powered up? - YES!

This may not seem like much progress, but this data proves that the full digital system configuration is totally doable. I might even remove the factory amp and see if one of the aftermarket amps can fit in that location (it's a tight fit though, so we'll see).

 

[Victorofhavoc]

Just a note for the future when identifying things @ashmostro, I've had really good luck with getting Ai (chatgpt, Claude, and copilot) to identify fittings, ports, and such by photo. A neighbor lost one of my power plugs for a beefy 120W RMS Bluetooth speaker, and I couldn't find it anywhere. One photo to Claude and it found a myriad of sources in whatever length and finish of choosing.

 

[ashmostro]

I used AI for a lot of this but it was pretty useless for the newer non-documented connectors like the 26 pin one I took months to find. It's literally not even on the manufacturer's website yet, so AI was totally useless and pointed me to the wrong connectors over and over again.

We're not at AGI yet....

 

[Victorofhavoc]

I used AI for a lot of this but it was pretty useless for the newer non-documented connectors like the 26 pin one I took months to find. It's literally not even on the manufacturer's website yet, so AI was totally useless and pointed me to the wrong connectors over and over again.

We're not at AGI yet....

Yeah we're not, but we are getting slightly closer on some ends. When I can get an ai to truly replace me, I'll be in my happy place!

 

[ashmostro]

Further "inside baseball" for anyone who wants to do this in the future (specifically, to run an unaltered digital input to your DSP while retaining the factory volume control knob):

Prerequisites to being able to do this on our cars:

1. You need a DSP amplifier that uses a simple 3-terminal potentiometer for its optional external volume control function (some DSP amps use a proprietary digital signal for volume control and a fancy touchscreen... this isn't in scope for my solution)
   • One of the big reasons I went with Arc Audio is because it was the only brand I found that allows you to do a manual calibration of the volume controller within the DSP software. This meant I could use a non-Arc Audio potentiometer to control the volume because I can calibrate the amp to it within the software.
2. Your DSP amplifier can simultaneously merge and play digital and analog inputs and has user-definable "ducking" as an option, which allows you to feed in chimes, beeps, gongs, phone calls, etc via analog connection, and then program the DSP to attenuate the digital signal whenever it "hears" any of those analog inputs producing a signal (e.g. you are backing up and your rear proximity sensors are beeping - you don't want those drowned out by loud music)

Parts you will need:

1. Arduino Nano Every- programmable open source microcontroller. This is where the logic for converting the factory RS485 volume signal into a variable resistance lives.
   • The Arduino will need to be programmed to understand how to convert the signal. If you want to tackle this project, contact me to get the source code.
2. TTL to RS485 Serial UART Automatic Flow Control Module - this converts the RS485 signal from the car into an industry standard protocol the Arduino can understand (Universal Asynchronous Receiver-Transmitter).
3. Arduino Nano Every Breakout Shields Board - To make connecting the Arduino terminals less painful (less soldering)
4. DS3502 I2C Digital 10K Potentiometer - this is on the output side of the Arduino and is controlled by the Arduino to produce the linear varistor output that the DSP "sees" on its volume control input connector
5. Mean-Well Isolated 5V Power Supply - to provide clean power without any possibility of ground loop hum.
6. Some sort of project enclosure - to make it self-contained and pretty

The physical connection flow looks like this:

Factory Head Unit RS485 output signal -->[ TTL to RS485 Flow Control Module --> Arduino --> DS3502 Digipot ] --> DSP Amplifier volume control input connector​

The items above in [brackets] are powered by the Mean-Well isolated power supply which in turn is connected to one of the car's many 12V accessory outlets (i.e. a cigarette lighter terminal).


Happy to answer any questions or receive feedback if you see anything amiss above. I have not yet built the converter as I'm waiting on parts.

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