If there's one single element of the whole car audio scene that gets the most attention, it has to be bass. It's what got most of you into car audio (me included), and it's what keeps many people interested in the sport. I know this for a fact, and that fact is reinforced every time I get an e-mail question about "bass related topics" from you guys. No matter what type of system you have, from a simple street pounder to a high-end IASCA competitor, it's not complete until it has a good solid bottom end. Since I get so many questions about bass, I decided to dedicate a few articles to this very complex topic.
There are many elements involved in selecting a subwoofer system for your car. The first (and most important) thing you have to decide is what type and the amount of bass you want. This decision is key, since it will affect what type of woofers, amps, and enclosures you will use in your car. It boils down to what type of music you really like to listen to. If you love the boomy, loud bass found in hip-hop and R&B, your optimum system will probably be different from the guy who listens to a lot of jazz. It's possible to build a system that can play everything, though it might not be optimized for any one type of sound. Be honest with yourself (and your installer) when choosing the sound you want so you can get the most enjoyment out of your system.
Now that you know the goals for your bass, it's time to select the equipment that's right for you. Assuming you have adequate amplifier power, there are three main elements that affect in-car bass: the woofer, the enclosure, and where the enclosure is located in the car. Get any one of them wrong, and you'll end up wasting your money on equipment that doesn't perform right. Let's take a look at each one of these elements so that you'll have the knowledge to make the right choices for your system.
The first and most obvious choice you have to make is the subwoofer itself. Fortunately for you, the market is flooded with quality subs that perform great without breaking the bank. You can buy really nice subs nowadays for under $300.00 that will shake the fillings out of your teeth if you set them up correctly in the car. The key, of course, is to get the right woofer combined with the right enclosure loaded properly in your car.
There are a few basic performance specs that you need to know about when it comes to woofers. These specs (also known as Theile/Small parameters) affect how the woofer will perform in different types of enclosures. The first of these is called the resonance frequency. Take a rubber band, stretch it between your fingers, and snap it - it will vibrate, or resonate, at a certain rate. That rate is the natural resonance frequency, and a woofer works exactly the same way. Most subs have a resonance below 35 hertz (1 "hertz" is one vibration per second) which makes them good for low bass. It's good to have a low resonance frequency, since many enclosures raise this frequency (more on this later).
The second thing to keep in mind is the Q factor. This one's a little more difficult to explain, but I'll do my best. Basically, we already know that a woofer resonates at a certain frequency, and by definition it is the most efficient at that frequency since it naturally wants to vibrate there. The Q factor describes how much of a peak it will have at that frequency. A Q of 0.7 or so means that the woofer will not have a bump, or peak, in output level at the resonance frequency. A higher Q means that as the woofer gets near its resonance frequency, it will play significantly louder than it will at any other frequencies. Like resonance frequency, the Q increases in some types of enclosures, so you have to look at the woofer/box combo to see how the system will perform together.