Over the past few months, I've been collecting parts to put together a good - not great - system for the Trans Am. My overarching goal was to improve the sound quality, not necessarily make it loud enough to deaden my already old hearing. I also wanted to make the system completely hidden, as my car does not have the cargo shade to hide anything in the back. That lead me towards a setup that would fit in the rear tire well. There were a few pictures here on TGO, but most were old enough that the images were no longer there. Thought I would put detail the system I put together in hopes it might help others.

It started when I picked up a set of Sony Xplod 4x6s and 6x9s at the local pull-a-part yard for $30. Then I got the urge to hook up an amp and subwoofer as I could now tell that the lower frequencies were not coming out at all. After scouring Facebook Marketplace and Craigslist, I got my hands on a nice amp and sub. The amp is a 5 channel Kenwood eXcelon XR901-5 (I think) that a real audiophile was selling after getting a new system for his BMW. Picked that up for $200. The sub is an Alpine Kappa 10" - 100w.9 that I picked up for $100. I needed a line out converter to go from my factory (00 Grand Prix) head unit speaker-level outputs to the RCA jacks on the amp. Selected a DS18 V5HL as it had the basic features and found a new one on eBay for $45. Last was the wiring - new 4 AWG welding cable that I sourced on eBay for $45 for 30' and new SpeedWire at 20' for $20 (should have purchased about 25, would have made life easier). MDF for the speaker box was $5 from a local guy that builds poker tables and has large pieces of scrap.

Once all the parts were gathered, I got to work on the installation. I wanted to hide all the wiring, so I opted to remove the headlights and bumper cover to run the amp power wire along the front of the car with the headlight harness. Once on the passenger side, I used some harness clips and drilled some small mounting holes so the power cable runs under the inner fender frame rail. It enters the cabin between the power antenna grommet and the ECM wiring.

Power wire runs along the headlight harness to the passenger side fender

Had to drill a hole for the power line to enter the cabin. Nicely sized for the grommet.

View from the kick panel side.

Rest of the power cable routing was easy - along the passenger side rocker panel and up the rear wheel well until it exited at the spare tire area.

I used the SpeedWire for both speaker inputs and outputs. It is routed from the spare tire area to the center console and up to the head unit.

Speaker wires tucked into the console area. I used an adapter between the factory radio and car harness so I wouldn't need to splice directly into those wires.


The mess of wires. Plenty of power cable, not so much on the speaker wires.

 

With the wiring in place, I began on the subwoofer box construction. The space looks a lot bigger until you start trying to fit a box in there! I ended up having to cut out the spare tire brace to make room. Wasn't my first choice, but I have no spare tire or jack and there was just no way to thin the box out enough. The sub depth is 6", I ended up with about 1/2" of clearance between the sub magnet and the back of the box. Besides, been a AAA member for plenty of years!

CAD - Cardboard Aided Design

Box built and ready to cut out the subwoofer hole

Test fitting the box after the spare tire brace is removed.

Final external dimensions of the box are roughly 17" tall, 16" wide and 7" deep. The ideal interior space for this sub is 0.75 cuft - which I first planned with a 17" by 17" box, but had to trim 1" off to allow it to fit. So, it's a tad small but works fine.

Amp and line out converter are mounted to the box, then it is braced with brackets from the rear tire seam and the left over part of the spare tire brace at that attaches to the rear fender.

All mounted in.

After tuning the amp gain and crossover filters, I'm very pleased with the end result. The setup provides - at least to my VERY non-expert ears - a full spread of sound. The equalizer on the head unit is ideal because I can use the lower frequencies to dial in the amount of bass for each song. Still working through the fine tuning.

Anyway, a lot of fun to do. Nice thing about playing with the sound is that if something goes wrong - you're not stranded by the side of the road. Just no tunes.

 

Nice job. Are you going to install the interior plastic right over it or will you modify it and add a speaker grill? I’m doing a similar installation on the driver’s side.

 

I installed the stock cover over the sub and amp. One of my primary goals is a hidden system, so I did not want anything visible.

 

thats pretty cool

 

not quite following where the amp is located or what it is connected to? would love to have a factory looking system, that actually sounded good.

 

All is screwed to top of sub box, can be seen in the final picture. You are in Austin? I'm out towards Dripping Springs, you would be welcome to come see it first hand anytime.

 

Hey Thainglo - I was just thinking about you the other day as we were passing thru D.S. on our way to San Antonio. I definitely need to swing by and say hi sometime. Maybe even bring the Formula out!

 

Sending you a PM with direct contact info