I then had to tackle running wiring back to the spare tire area, both power and speakers. The power wire was relatively easy, as there is a large rubber grommet that's easily accessible above the driver's feet and then from inside the "engine" compartment. I stabbed through it with a utility knife and was able to push a 4-gauge wire through rather easily:

At the battery there is a plastic cover for the positive terminal, so I still have a little work to do out there - namely cut a notch into the plastic cover so the power wire can come out while the cover still closes down all the way. There are a few metal plates which encase and cover the positive terminal too, so those need to be worked around by the power wire. But these are covered in a rubber insulating material, so I appreciate that, and there is space between them and the battery for the fuse holder, so I was able to keep the non-fuse-protected wire run very short and very non-exposed, since everything it's close to is either the plastic casing of the battery itself or this rubber-encased metal plating. (I will try to update this post with pictures of this area once I clean it up this next weekend.)

As for the signal and return wiring, there is ample space to route this wiring from the footwell back to the spare tire area. The trim along the floorboards come up easily, just typical clips, and there is already a track with wiring running along there so it was pretty easy to just follow that.

That return wiring sheath is rather thick (it was overkill to get 16ga, admittedly, and it's designed for more industrial applications so the rubber sheath encasing it all is thick. But down under the Bolt's seats is a little channel that I could pass it through, so that helped quite a bit. Otherwise it was pretty easy and straightforward - just dodge the various bits of styrofoam and the clip points where the trim attaches, and you can get to the spare tire well easily. There's even a little notch in one of the styrofoam pieces just behind the rear seats, as you're entering the spare tire well, that accommodated the signal/return wires on the passenger side and the power wiring on the driver's side.

With that all the wiring I needed was in place. I also ran a wire down the driver's side for the amp's remote controller, and routed an AUX wire and a digital optical cable down the passenger side, since the Audison amp carries these inputs too.

Next up was building an amp rack, of sorts, for the spare tire well. For that I started with a flat piece of wood, just whatever my local hardware store had. I cut down a piece of carboard until it was the right shape and size for the well, and used that cardboard as a template. It took a few rounds of cutting and sanding, but eventually I got the wood into the right shape.

To hold it down I got a threaded post that matched the thread in the already-existing bracket. This bracket held down the foam insert I removed, so it was easy to match the thread. This post also holds down the grounding wires, which I bolted down to the bracket after sanding off a little paint.

Oh, and those practice golf balls? That's my high-tech answer to the problem of those several screws poking up from the bottom of the wheel well. I didn't want to hack them off, and I needed something to hold the wooden amp rack down and against, so I got these foam golf balls, poked a hole into one side, and pushed them down onto the various protruding screws. They all seem to be the same height off the bottom of the well:

So then the piece of wood is held fast against them by the wingnut I've hand-tightened from the top:

And voila! The wooden amp rack is floating on a foamy base, somewhat-isolated from bumping and jostling. And this maximized usable surface area on the amp rack since I only needed to attach / hold down the amp rack at one point, via that wingnut.

No no, this is not a professional job. But I never said it would be!

 

And now, the final phase - speaker installation. This was pretty straightforward, as I used these mounting brackets and these wiring harnesses to make it easy at the doors:

Scosche SAGMHR-634 Speaker Mounting Brackets

Install 6-1/2" or 6-3/4" speakers in select 2005-up vehicles

www.crutchfield.com

American International SH3802 Speaker Wiring Harness

For select 2014-up General Motors vehicles

www.crutchfield.com

Add in some dynamat and this is what we typically ended up with:

The Audison Voce speakers all required more modification of those speaker brackets to get them to fit, thanks to their basket designs. At this point I was at a cousin's house scrambling to get the job done in time for a family dinner, so I didn't take great pictures - sorry. But each of the woofers fit well, and did not interfere with the windows in the door, after some dremel work.

For the tweeters, I pulled the stock grill / trim pieces out (pretty easy, as they're just attached with clips - no need to remove the A-pillar either. But the stock tweeters fit inside a sheath on the underside of the stock trim piece, not likely suitable for most aftermarket units:

So for my project I cut out the stock grille and cut off all that sheathing, so the Audison tweeters could just surface-mount onto the trim.

The stock tweeters use a wiring harness, thankfully, so I just disconnected them and left that hanging up in my dashboard. I had read somewhere that the stock tweeters are wired in series with the stock woofers, so I was concerned about doing this. But the wiring diagram I found has them wired in parallel, which I can confirm is correct since my woofers still work on the stock wiring even without the tweeters attached. (And my multimeter reads 4 ohms, which is what the woofers are rated, so I'm confident that stock tweeter wiring is now just a dead circuit hanging harmlessly off the front doors' woofer circuits.) I then dropped new wiring through the tweeter holes in my dashboard, fished it out easily down in the footwells, and ran it over to those two extra channels coming back up from my amplifier. Connected those to the aftermarket tweeters, popped all the trim clips back in place, and I had a fully active system in place, with no stock wiring modified and only the tweeters' trim pieces cut apart in a way that can't be undone. But new trim pieces aren't a difficult part to find, so if I ever want to go back to stock I can just buy two new corner-dashboard trim pieces, fit the stock tweeters back into them, and everything else is easy!

Here's the amp "rack" with the amps bolted down to them:

The subwoofer's output wiring still needs work - don't worry, I won't be relying on those twist-on nuts forever. I just wanted to get 'er up and running that day is all. I have all the parts and plan to custom-build an end-to-end harness with those 4-pin Molex connectors, maybe even tonight.

Above this spare tire well is the first of two cargo areas for the Bolt EV. The carpet covering this is flimsy, as the styrofoam insert I removed provided a "floor" so the carpet doesn't need its own structural integrity. But I want cargo and my subwoofer box to sit in this area, so I needed to do something to form a new "roof" above my amp rack and support the carpet floor / subwoofer box above. Here's what I came up with:

It may not be pretty, but the price was right (free, since it was just spare piece of MDF stuff floating around my friend's garage) and it works well. Cut it to the right width and then bolted a piece of wood on the bottom for structural integrity:

With that the carpeting floor sits flush, and the wires for the subwoofer pass up through the hand hole.

The system is now fully-functional. I still have some work to do with tuning it and the like, but overall I'm quite pleased. I know there are many prettier installs out there, but I take pride in having done this myself and knowing exactly how the wiring harness was done, for example. And even without having done any detailed tuning yet, it sounds amazing! So much more capable than the stock crap that was in there before.

Hopefully this can serve as a resource for any other Bolt owners out there who decide to overhaul their system. Always available to answer questions or troubleshoot things with folks who embark on the journey!!

 

thanks for your post it definitely helped me, i have a 2023 EUV that i put a system in, Scan 18w, scan tweets, Helix Psix and sub, i used the extension harness you mentioned with the same bent pin problem(weird) so did you ever figure out how to make the stock chimes and things work again? i don't really care so much about the chimes but the apple car play directions while using google maps are too low and i wish there was a way to make that louder or mute the music more.

 

did you ever figure out how to make the stock chimes and things work again? i don't really care so much about the chimes but the apple car play directions while using google maps are too low and i wish there was a way to make that louder or mute the music more.

Yes, I got my stock chimes working again. That depends on which amp you use, and if / whether it has some circuitry designed for this situation. You have to trick the stock system into thinking the stock speakers are still connected, either by adding a resistor in-line before the speaker-level signals hit your amp's input or using a processor or amp with built-in circuitry for that.

What is your signal path? If your speaker-level inputs are feeding into the Helix P Six, I'm surprised the chimes are not working. I'm now using a Helix DSP and my chimes have worked flawlessly, and those should have the same ADEP circuitry inside. (Which P Six do you have? There have been several iterations, which have used either ADEP or ADEP.3.)

If your other noises (CarPlay directions, etc.) are too soft, something tells me something strange is happening. And do your door chimes / turn signal noise / backup alerts work at all? Are they just quiet, or are they gone altogether?

 

they are just all quieter than normal, I have speaker level into the psix

 

And what's your source?

The chimes and what not are a fixed volume, they're not controlled by the head unit's volume knob. So the gains on the amp (and in my car the DSP's own volume knob) will change the level of the chimes, but nothing else will.

So your amp's gains need to come up a bit to make the chimes louder. If that makes your music too loud you'll have to turn down the volume on just the music's source.

 

Factory HU for now, I will try adjusting the gains on the PSIX, I have a couple of Pure I20's around but not sure if I'm going to bother, thanks for the info.

 

Sorry, I should have clarified - I know you’re on the stock HU still (anyone out there who swaps out to an aftermarket unit will be a legend). I mean, is your source Bluetooth? CarPlay? Radio?

Or I suppose you could be inputting directly into the amp, via an aux input or the like. But if you’re using the head unit, maybe the volume on the source you’re using through it can be adjusted.

 

Maybe I missed it, what are you using to send 12v amp power / turn on signal. What did you end up tapping into from the car to turn on the amp?

 

Nothing - my Helix DSP turns on automatically when it senses a signal on the high-level inputs.

Then it provides a remote turn-on I could use for the amps.

 

Planning on using Matt's pro audio amp and a audio control lc6i. I just checked out the specs, it does mention "The addition of internal summing capabilities and improved GTO™ signal-sense turn-on"

I had not even realized it did that.

 

Yeah, you’re good then - the LC6i has it handled.

Now the question will be whether your turn signal and door chimes are preserved. I’m not familiar with what the LC6i does for that, if anything

 

Is it just a matter of the system being asleep when no sounds playing, or something else happening?

 

No, it’s something else. The Bolt’s stock system is doing…something to “look” for the stock speakers. If it doesn’t like what it sees when it “looks” it doesn’t play auxiliary sounds, such as door-open chimes, turn signal noises, or the several safety alerts.

I never figured out exactly what it does to “look,” but you can make it like what it sees by having enough impedance on the speaker lines (i.e. what you’ll be using as the high-level input). Some devices have a solution built in, like my DSP. Not sure what LC6i does here. And if the LC6i doesn’t fix the issue on its own, you’ll have to add a module or resistor(s) just before the LC6i to keep the stock system happily playing aux sounds.

I actually have just the thing that should work, if you need another solution beyond the LC6i

 

It would be great to have the resource ready to reference if I do run into that. But also for anyone else researching how to do this. I would greatly appreciate whatever information or recommendation you have to fix it.

 

I have a module from Audison called a USS4. It’s an impedance simulator, so the system thinks the stock speakers are still connected. I didn’t actually use this module in my Bolt, but I believe it would work. I would sell it to you for a nominal amount.

Or, I believe other Bolt owners had success with Audio Control’s AC-LGD resistors, which essentially do the same thing - add a resistive load to the stock speaker wires so the system thinks everything is normal.

My system works properly with my Helix DSP, which has circuitry built in to address this issue. Exactly what that “ADEP.3” circuit does I’m not certain, but I’d bet it just adds some add’l resistance at the high-level input terminal.

Before the Helix I had an Audison AP 8.9 DSP/amplifier. That unit does not have integrated circuitry for this, so I lost my aux sounds. But it does have an optional, external module for the issue (the ASP-18) which solved the problem and got me my aux sounds back once I started using it.