When I first got into car audio, big bass drove my passion. Like many teenagers, I was willing to sacrifice, so I yanked out the backseat of my '70 Chevy Nova and replaced it with a huge 8ft3 vented enclosure securing a pair of Cerwin Vega 15's. Powered by a couple Orion "Red" amps, my '70s rattle box was insanely LOUD! And, that is exactly what I wanted.
Before I started that system, I determined that a vented enclosure was needed in order to achieve the biggest possible output, completely disregarding sound quality. This meant choosing a subwoofer best suited for this application. While driver choices were fewer back in the day, there were still several to choose between. After a little research, I landed a pair of CV's based on their reputation at the time, and the simple fact that they were one of the few speakers designed specifically for use in ported enclosures.
However, in today's market the choices are getting increasingly complicated. Not only are there a plethora of subwoofers to choose from, the line between driver enclosure requirements has blurred. Fortunately, more speakers are now designed to be neutral, working in several box styles, which means better options for the consumer. Yet, choosing the right enclosure is still a complicated matter.
The following tutorial is designed to help guide you through the pros and cons of the most popular enclosure styles of today. There's no "magic box," but you might find some enclosures to better suit your requirements. Hopefully, this will help you make a better decision in your next audio system.
Infinite BaffleInfinite Baffles (IB) are possibly the simplest enclosures to build and a great way to conserve space in your vehicle. The concept of an IB is to isolate the sound wave produced by the front of a speaker cone from that of the wave produced by the rear without actually using a solid chamber to reinforce the sound - within a vehicle. In its most basic form, the design of an IB involves mounting the speaker(s) on a baffle board that partitions off a section of the vehicle. Because of this, sedans and vehicles with a semi-isolated trunk make the best candidates. For example, let's use a sedan: By mounting and sealing a baffle to the generally large opening behind the rear seatback, the trunk now becomes an enclosure for the subwoofer(s).
IBs are also termed "free air" systems because the trunk space - now the enclosure - typically contains a greater volume of air than is depicted by the VAS parameter of a speaker.
Unfortunately, trade-offs come in many forms when working with IBs, most of which relate to efficiency. Of these, structural integrity, leaky divisions and low bass extension top the list. Without a solid structure surrounding the woofer(s), it's difficult to reinforce the audio. Trunk interiors are notoriously designed with flimsy panels, thin sheet metal and often a spare tire - each of which can diffuse the energy produced by the subwoofer. This diffusion can contribute to vibration of the trunk's contents, causing cancellation, distortion and unwanted noises.