2003 2500HD Chevrolet Duramax Crew Cab

Subwoofer Installation Guide

My Chevrolet truck has the 6 speaker, 1 OEM Sub,  factory Bose sound system with the factory amp and dual coil subwoofer in the center console. I wanted more bass and decided to add a set of subs to the truck. I added two 10" MTX Thunder 5500 subs ($129ea) in a dual downfire box that I purchased from subthump ($168) and I used a PAC adapter ($50) to get line out levels from the factory radio unit.

(Note: If you order from subthump.com, tell them you heard about them from this website.)

Photos of my installation can be found at the bottom of this page. Click on any photo for a full size detailed photo.

Specifications on the MTX 5510s:

Specifications on the subthump enclosure:

Specifications on my Kenwood KAC-927 Amp

Other Items

I also have installed a 1.25 farad capacitor to help out on the deep notes. This has nearly eliminated any strain on the electrical system. This normally is noticed by dimming headlamps or dome lights at night when the subs are cranked. I also put poly fill in the sub box to make for tighter bass.

I also purchased two Sony 10" subs from Best Buy to try out in my configuration.. They have a higher Peak RMS rating (1200 watts) as well as a wider range of frequency response (18Hz - 2.5 kHz), however, because they have this wider frequency range, it appears they are unable to re-create the lower bass notes as well as the MTXs. The Sony's cost only $95 a piece. I was more pleased with the quality, clarity and deepness of the MTX subs with this enclosure for now, so I have kept the MTXs.

How does it sound?

So how does it sound? Awesome. It is very comparable to the dual 12s in a vented box I had in my Tahoe and Suburban, using the same amp. The system now hits so hard, I'd get a headache if I left it cranked too long. The down fire 10s are definitely the way to go and they hit hard with great clarity. The bass is not a muddy wash, but very distinct. I suppose if I put a bigger amp in, it'd be deathly loud, but the Kenwood is kicking some serious A$$ that I have no need to upgrade amp for now. (Unless I blow it...hehehehe) Be sure to chose a good sub though, the cheap $50 subs will sound like crap, regardless of what box you stick them in. I am sure if I bought $300 subs, it'd sound even better.

In my tweaking, I played songs from Bon Jovi, to ATC, from Country, to ROCK, to POP, you name it, I played it in the truck and was amazed of the accurate response of the setup I now have. I tossed some mix/dance cds in and they sounded great too. I do not have XM activated, so I did not try an XM feed. I had my wife come out and sit in the driver seat and then play a CD that had some serious bass too it, she looked at me, laughed and gave it the thumbs up!!

I'd like to replace the Kenwood amp at some point with an amp that has remote bass controls. Right now I use the BASS knob on my factory radio to adjust the bass. The problem with this is it does affect the level of bass (lower notes) that come out of the stock speakers. If I turn the bass all the way down, then the stock speakers sound a little week. However, since I run the bass at about 50%, it is ok.

I can almost guarantee that you will be extremely pleased with this setup. Buy a box from www.subthump.com today. I did run the dual box with a single 10 for a few minutes, and it still hit real hard. so for those of you who decide to get the single 10" down fire box, it will sound awesome too!


Click on a thumbnail for a larger image.

The box is well built and custom made for the 2500/3500HD crew cabs.

I had to re-adjust the jack bracket so the box would fit in. I simply unbolted the jack bracket, drilled a new hole in the bracket and re-mounted it in its new place.

The box fits under the seat nicely. My only dislike is that if a heavy person (200+ lbs) sits in the back seat, they can somewhat feel the top of the box under the seat. This could make for an uncomfortable ride on a long trip. A light person (115-120 lbs) was not able to feel the top of the box. The box has to have these protrusions to be able to allow a mounting depth of 6" for a sub.

The rear seats do not fold all the way forward. They fold far enough forward that I am able to access the storage area behind the seat for tools, gloves and other miscellaneous items. You can also see how I was able to install my amp with no screws.

 PAC AOEM-GM24 Adapter Setup

I used a PAC adapter to get a clean line out from my factory head end radio/cd/xm receiver. I ordered the PAC adapter from ebay, although a number of vendors carry them. Price ranges from $40 to $75. If you put a new head end unit in, get one that has sub-preamp outputs. Then you will not need this PAC adatper.

*You would want to purchase a different adapter that interfaces with the steering wheel controls and Onstar, if your vehicle is equipped.*

I had to pop off the dash cover to access the radio. This was real easy, to do as they are expansion snaps that hold it on. I removed the 4 screws that hold the radio in and popped the radio out. I followed the directions that came with the PAC adapter to hook it up. It really is a simple plug and play hookup.  I hooked the RCAs to the REAR outputs of the PAC adapter. I then ran two RCA cables down the center console under the passenger seat and to the amp mounted behind the rear crew-cab seat. The PAC adapter does provide an AMP power control wire, this turns the amp off when you turn the radio off.

I configured my amp to bridge the output to my dual 10" subs that I wired up in series.

Hope this helps you. I am by no means an expert on this and am not responsible for anything you do to your truck. This information is provided as-is and could void your audio system warranty.

I originally had a single 10" in a box behind the rear seat,. See how I did that here. My original single 10" setup.

No spam please, but you can email questions to me:  duramax  (at) onlinedesk.net

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Last Update: 07/26/2005

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