Edit: This thread is obsolete. The thread remains for historical purposes. Refer to the SQ Car Audio V2 thread: http://www.cruzetalk.com/forum/36-gen1-audio-electronics/11204-sq-car-audio-thread-v2.html
This is going to be the mother of all SQ car audio threads.
In this thread, I'm going to show you how to install a full-fledged SQ based sound system in your Cruze that you could probably compete with. Some of this may go over your head, but with a bit of research, questions, and learning, you'll be able to do what I'm about to do.
This system will be based on Sound Quality
(SQ), not SPL (sound pressure level), although it will reach SPL levels capable enough to cause hearing loss with prolonged exposure. The goal is to create a system that sounds as good as a system can possibly sound on a modest budget. I will explain all of the decisions I make so you can learn more about car audio as well as help you make your own decisions with your own installs. This will probably take a month or two for me to finish.
This initial post will be dedicated to outlining concepts I will use while documenting this project. Let's start.
What makes a good SQ system?
Ever heard a bass thumping ride rolling down your neighborhood? That's not what we're going to do here. If you sat in that car, all you'd hear is bass. If you're competing in SPL competitions or trying to impress some kids, that's fine, but if you want to enjoy your music the way it was recorded, you're going to need to learn how to accept bass in moderation. SPL gets old after a while. Almost every car audio enthusiast I've known eventually passes the SPL phase and spends his/her time in SQ. We need a balance between bass and front sound stage. When you get in your car and turn the radio on, you shouldn't be able to tell that the sub is in the trunk. It should sound like it's everywhere, it should be tonally accurate, and most of all, it should blend well with the front stage.
There are two approaches to car audio. The first is the "more speakers are better" approach. This train of thought implies that the more speakers you have, the more "full" and "rich" the system will sound. The truth of the matter is that this isn't true. Your goal is to reproduce the recording as true to it's source as possible. If you can reproduce a live sound stage, you're even better off. Home theater companies sell you on this with 5.1, 6.1, 7.1, and beyond, implying that more speakers are better. For movies and surround effects, the point can be validly argued, but for music, you need a front sound stage, not a surround sound stage.
This system will focus all energy and resources on the front speakers in an effort to reproduce a realistic front sound stage and not blow the budget. We don't want an "in the club" feel, but we do want the sound to be rich and full. This will be an upgrade to the non-pioneer system. The rear deck will remain empty, while the front speakers and tweeters will be replaced, and the door speakers will remain, but with high pass filters designed to cut off bass frequencies to prevent distortion. The only reason I'm leaving the rear doors in is so that my rear passengers have something to listen to. Otherwise, I'd remove those as well as they will be faded out when I'm alone in the car. Once you hear a well-designed sound stage in a car, you'll always feel like something is wrong when listening with rear speakers playing.
Component speaker kits are designed with passive crossovers to tame midwoofer cone breakup and protect the tweeter from playing too low of a frequency. These however do not have any reasonable equalization, phase alignment, or time alignment capability. In order to achieve a reasonably flat frequency response around the Cruze, we need to go digital. This system will use a MiniDSP digital processor and purpose-selected speakers to achieve my goals. The MiniDSP allows me to select any crossover point and slope up to a 4th order LR on both the tweeter and midwoofer, as well as provides me with a 31-band equalizer. The speakers will be measured with a Dayton MM-6 measurement microphone with an M-Audio microphone pre-amp in order to get as flat of a frequency response as possible.
The subwoofer's box will be designed with JBagby's WBCD and BDS spreadsheets to predict and model cabin pressurization gain, boundary loading, and apply those to the sub's frequency response based on it's T/S parameters. This way, we don't need to spend money on a PEQ for the sub amp and can get a reasonably flat frequency response out of it.
This is undeniably one of the most important and most under-estimated aspects of a car audio install. You need to reduce vibrations, reduce noise, and separate your midwoofer's back waves from the front waves in order to give you a strong midbass presence, but without fatiguing resonances and distortions. The doors, trunk, and trunklid will be effectively treated with deadener, and I will teach you how to do that.
Stealth vs Axis Response
Our first compromise will be in favor of stealth. I live in the Chicago area, and the last thing I need is people knowing there's a system in my car when I take my friends and family downtown during visits. For this reason, I will not be making custom pods for the tweeters to be mounted to the pillars. This is a compromise because tweeters perform best when listened to entirely on-axis, near ear height, directed at you. It is my biggest compromise, but I need this to look completely factory through the windows without any indication that there's something worth stealing inside. For this reason, the factory head unit will also remain and a GM-specific PAC LOC will be used. My tweeter choice will help alleviate the impact of this compromise.
Cost vs Sound Quality & SPL
Naturally, I could spend more money on better midwoofers, a second subwoofer, and newer amplifiers, but let's face it, I drive a Cruze Eco. This system will touch on some of the bare minimums of what one can spend to get world class sound quality in their Cruze.