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2005 Pontiac GTO - Long Overdue Refresh

8157 Views 49 Replies 13 Participants Last post by  Stoopalini
I've owned this car since 2010, and it's been through a lot of iterations over those 11 years. For 3-4 years, it was a dedicated road course car even ... but I retired it from the track in ~2014, and converted it back to mostly stock form, to turn into a nice daily driver (even though it only gets driven a 2k miles a year or so).

Back then, I put a Pioneer 80PRS head unit it, and dug out my old amps and installed them as well. A Rockford Fosgate Punch 250a2, and a PPI 4240. Definitely two old school amps :) I also threw some MB Quart components up front, some Tang Band 6.5" subs in the rear deck, and disconnected the rear speakers all together. For power, I installed a two-fuse block under the hood, and ran two 8ga power wires back to the trunk.

So here is where I started this refresh from:

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... And this is how the car has been since 2014 until just a few months ago when I decided to refresh the system due to me driving the car a lot more often lately.

At 1st, I just wanted better bass in the car, so I replaced the Tang Band subs + RF Punch 250a2 setup with a Rockford Fosgate P300-12, which is a self-contained 12" woofer and 300w amp, in a sealed enclosure. I also moved the RF amp to the 6.5" door speakers, to give them more wattage, since the punch 250 delivers 50wx2 vs the PPI which is 30wx4.

Here was the result:

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This definitely added the low extension I was looking for, but it still wasn't up to par on what I was looking for in terms of clarity.

So the next thing I decided to do was replace the components with something higher end, and get a single 4-channel amp with more power, to simplify the amp setup and significantly clean up the trunk space.

So I picked up some Hertz Cento components, and decided to try the new Toro class A/B amplifier as well. So my end state at that time, was to arrive at the following:

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As I started reading more, and planning the install ... I decided that I should do some sound treatment while the doors were apart ... which led me to gutting the interior and treating everything (not just the doors) with second skin CLD, MLV and CCF. Man, what a slippery slope this can be!

Then I started thinking about the power, and questioning the two 8ga power runs to the trunk. Learning about CCA vs OFC, and everything else which comes along with that topic. Having a power distribution like this:

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... while it may technically "work", I began to realize it was far from ideal and wouldn't provide me with any room to scale up in the future. So I decided to replace the power and ground wires too ... I mean, I'm in this far, right? So why not ....

So I ended up swapping out the two 8ga CCA runs with a single 2ga OFC run, added two distro blocks in the trunk, 4ga OFC runs to the amps ... for both the power and the ground wiring ... resulting in this:

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Ok, so this is pretty good, right? The sound definitely improved all around .... sound deadened, MLV blocking road noise, CCF removing rattles, Hertz components, more power on tap ... I even upgraded the grounds under the hood ... but ... still, I felt the clarity wasn't quite what I wanted.

So more reading, more research, and of course ... I need to tune the system with more than just my ears ....
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Very nice work! I love your “Rabbit Hole” comments...are we ever done?
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My Jaguar has the gas tank behind the rear seat like your GTO and I never could get decent sounding bass in to the cabin from the trunk area so I gave up on that. It all started when the factory 6x9 "sub woofer" gave up the ghost as the foam surround crumbled. I ended up removing the stock sub, fabricated a new mounting ring and replaced it with a PowerBass 6x9 sub that does pretty decent for what it is. My car also has solid steel between the rear seat and the gas tank with a lot of sound insulation and I don't know if the GTO is like that or not?

I hope that in the end two 8" woofers IB works as I can't live without a trunk, need space for golf clubs. I think that if my Jag had two 6x9 subs it would be decent enough as I don't want to modify it to that degree either due to the nature of them getting harder to find in good condition.
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I didn’t even think about the fuel pump noise. my Jaguar has two fuel pumps, it runs on one when there is no boost from the supercharger and the second one kicks in to up the fuel pressure and volume when the engine sees boost. I never hear them at all, but my fox body Mustang is a different story.
Thanks for sharing and I'm glad that you are happy and it is working out. I recently started building the system in my 2021 VW Atlas Cross Sport and am in the process of testing sub configurations and drivers. I ran the power, ground, signal from the head unit to my DSP and wires to both doors to either run active or passive depending on which route I end up going. I am currently running and 8" Image Dynamics ID8 v.3 in a small sealed box and it sounds really nice. It does not go as low as I would like, but I have a Memphis Mojo Mini 8 that I am going to try next in both sealed and ported boxes next and I know it will play much louder and lower.
It's amazing the difference that a tweeter can make as for me it is covers the most sensitive part of our hearing. I seem to prefer tweeters with a lower fs and like to cross them over at 1800k - 2500k depending on where they are installed.
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