My goals were to improve the audio quality in my C7 without messing with the head unit and without making any obvious changes to the interior cosmetics. I didn't want to lose any cargo space or install custom enclosures. So a nice big amp was out of the question. I also wanted to spend the minimum I could get away with and still get a marked improvement in the sound.

I started with a minimalist approach. "Let's see if I can replace the easy speakers and leave everything else alone." I went to an installer who sold me on the Infinity line. He replaced the dash sides (tweeters), the small door mids, and the side rears. He told me that because the 8" door woofers were such a strange impedance (around 1.2 ohms!) we would never be able to replace them with a standard speaker and drive the replacements off the factory amp.

The result was a disaster. Very bad sound and a bad installation. To top it off, he wouldn't return any phone or email messages afterwards. I guess he didn't want to touch it again.

So that led me to a much more reputable installer. Even though this isn't a regional forum, I'd still like to give a big shout out to Radio-Active Car Audio in Garner, NC. They were a joy to work with and I would recommend them in a heartbeat.

We ended up keeping the dash and door Infinity speakers since I had already paid for them. The side rear speakers had been jammed into a hatchet job on the plastic trim cover and were delaminating (who knows why). So we replaced them with Phoenix Gold speakers that he had in stock.

The amp was obviously a critical component in the chain and needed to be replaced. Radio-Active recommended a mini amp package from Italian company Audison. We were able to stick two amps in the left rear cubbyhole for 8 channels of output.

That produced a significant improvement, but the BOSE door woofers were still responsible for too much of the sound and were obviously inferior to the other upgraded components. I came back for another round and upgraded the door woofers to Audison.

Now I've got a Frankenstein's monster of mismatched brands when it comes to speakers. Obviously I would not recommend that for someone approaching this as a complete project. You'll almost always get best audio imaging and consistency by going with a single line of speakers if you can. But I was saved by the advanced configuration provided with the Audison amps and a shop that knew how to use it.

The amps are the real find for this kind of installation. The next post will concentrate on details about the amps and installation.

 

I wanted to hide my aftermarket amp and the left rear cubbyhole seemed like the perfect spot. But that meant finding something with good audio quality and a tiny form factor.

Radio-Active recommended the Audison Prima line. This is a high quality automotive application product set coming from an Italian company. We used the AP4.9 bit amplifier for the first 4 channels of output. It includes a processor to configure the output and also has pre-outs for an extension amp (the AP4D) supporting an additional 4 channels. Power is rated at 70W per channel at 4 ohms and 130W at 2 ohms. So not a massive powerhouse, but offering clean sound in a very small package.

Getting all the signals from the factory amp required the addition of the Audison SPM4 4-channel stereo passive mixer. This mixes 4 channels down to 2 for getting to the right number of channel inputs for the amps. It is a very small box and fit nicely in the original amp compartment, centered between the two heat sinks.

We used Audison's tower kit to hold and stack the two amp units. They fit easily into the cubbyhole with room to spare. To provide ventilation, we cut a hole in the cubby lid and installed a metal grate. The carpet on the lid separated during this step, and getting matching carpet seems to be impossible, so we just re-covered with a mock CF vinyl, which looks fine to me.

Audison provides special computer processing programs for configuring the outputs to each channel. The tech sits in the car with a laptop computer and can adjust frequencies, crossovers, and volumes with great flexibility. My guys were great, doing an initial balance and then letting me sit in the car and dial-in my preferences to match my ears with my music choices.

I was very happy with the results we were able to achieve.

 

I should mention that I also added sound insulation to combat road noise. Yes, this adds weight, so track fanatics don't want it. But for road trips and a "grand tourer" application like I wanted, it was a must.

I chose the Exotic Vette pre-cut "Extreme Kit." It covered the cargo floor and driver/passenger flooring areas. It made a great difference and has my recommendation.

After we cut the ventilation hole in the rear cubbyhole lid, I found that the exhaust noise was coming through the thin rear body wall back there and resonated in the cavity. That was kind of fun when stepping on the gas, but ended up producing too much of a bass drone at normal highway cruising speeds. Unacceptable for long road trips, so we added a few sheets of insulation around the walls and floor of the hole and that helped immensely. I also had them throw a couple of sheets in the doors when they had the panels off to replace the woofers. It's a small incremental improvement, but easy to add while you have the doors exposed anyway. Might as well.

 

You will note that I didn't do anything to the subwoofer in the rear. I'd really need to add yet another Audison amp extension and then I'd be faced with trying to replace the speaker, which would have a low probability of success in BOSE's custom-designed enclosure. I didn't want to change the enclosure and rear cargo cosmetics, so I opted to leave it alone. I'm not a thumpity-thumpity sort of guy anyway, so this was not a priority for my needs.

 

Funny enough I am looking to do something similar (minimalist approach) and a highly respected shop near me is recommending Audison as well. Can you tell me which Audison woofers you put in the doors and what size? My installer is telling me he has some 8" Audison woofers he has used on Porsche's with great results.

 

Yep, we used the Audison Prima AP8 (8 inch). It is 4 ohm, which is very common. But coming from a 1.2 ohm factory speaker, that means the installer needs to crank more volume to it in order to get balance back to correct levels.

I have only had it in the car for a day, so I can't give you long-term impressions, but I was in the car for much of the audio tuning, and I was amazed at the difference in tonal characteristics it demonstrated with different software-enabled crossover and boost settings. It's hard to pin down a specific "sound" of the speaker. I definitely found that it improved vocals and spoken word to be much clearer and more listenable.

Good luck with your project!

 

Pac is coming out with a AP4-GM21/41 line output convertor that should make adding an amp to a C7 and other GM vehicles easy. These give you a sub control, ch output , 4-5volts of output at $249-299 retail. The AP4-CH41 for Chrysler are in and they can't keep em in stock.



Product Description

AmpPRO simplifies the installation of upgraded amplifiers in data-bus controlled sound systems. With AmpPRO, you can improve audio performance while keeping an original radio’s fit, finish and features.


Product Features

Variable volume, fade, balance, bass, mid and treble audio settings
Front, rear, sub preamp outputs (5 volt RMS)
Provides flat audio output for a solid audio foundation
Customized OE bass, mid and treble center frequency selection
Retains uConnect, Bluetooth audio and all warning chimes
Plug & play installation
Sub level controller
Optional TOSLINK optical output (APA-TOS1 sold separately)
Simplifies amplifier installation
Prevents need for summing and DSP devices
Provides factory sound system upgrade solution






I played around with this unit last week and it is awesome.
Its a great all in one solution.

 

This is awesome. So if I understand you can replace the speakers with no need rewrite them to the amp?

 

[QUOTE=thill444;1594429554]This is awesome. So if I understand you can replace the speakers with no need rewrite them to the amp?[/QUOTE

A few ways you could connect it would be to tap into your factory wiring at the factory amp.
If it were me I would just run new wires out of the aftermarket amplifiers that you are using.

 

these won't really show you much, but we all know that threads are worthless without pics!

Rear left compartment cover with metal ventilation grate and CF vinyl recovering.
Audison mini amps stacked in cubby hole.

 

Great write up ... I just completed a sound system in one of my toys and about to start the C7! Thank you!

 

Is this AP4-GM21/41 available yet?

 

I don't think the Amp Pro will cover C7 when they are released for GM ( I could be wrong ). As I understand it both of the C7 Bose systems use the MOST 50 protocol ( which is digital over copper )

The new NAV TV M650-GM does cover the car. They are spendy, but work very well.

 

This works on the C7 to replace the amp and speakers: https://pac-audio.com/catalog/amppro...faces/ap4-gm61

 

I wouldn't go as far as to say I'm an audiophile, but I definitely am disappointed in the Bose system in my c7. No midrange (my guess is somewhere in the 90 to 125 hz) bass to speak of. It's so annoying to just hear that dead spot in all of my music (everything save rap, and I do mean everything) what, if anything, has anyone found to solve this save a complete audio overhaul in the thousands of dollars range? Thanks

 

Ken, if you're ever bored, we should compare audio notes man. I'm in a C6Z, but audio is audio. I'd enjoy auditioning some Audison gear. It's a rarity around these parts. I'm just down the road in the Goldsboro area. (Like a 40 min drive). I also frequent the Garner?Clayton area. In case you want to see what I'm working with: https://www.corvetteforum.com/forums...y-install.html