Car Stereo Head Unit in Medley

The infinite baffle application is rare in the car audio world today because more than 75% of all vehicles are hatchbacks or SUVs. Also known as “Free Air,” this type of speaker enclosure is not an enclosure! It relies on a boundary or wall to separate the frontal waves of the speakers from canceling by those generated from the back. To accomplish this, building a wall (babble board) between the trunk area and the passenger compartment on a vehicle would be best. In my opinion, this is the best-sounding subwoofer application. It produces a tight and precise bass note that is not artificial or boomy! The best-sounding car I have ever heard of (Richard Clark’s 87’ Buick Grand National) employed a very similar setup with the addition of AP membranes. The infinite baffle setup offers superb sound quality with minimum weight while sacrificing SPL and power handling.

The sealed enclosure, or sealed subwoofer box, is as simple as it comes—a closed box designed to match the Vas or acoustic compliance of the drive. I have never been a true fan of the sealed enclosure for one reason and one reason only! Given the nature of the design, sealed subwoofer boxes could be more efficient and often require three to four times the power assigned to your mids and highs to keep the bass from getting drowned by the music. In other words, if you plan to have a 100-watt amp for your mids and highs, consider 400 to 500 watts for your sub. Sealed Enclosures allow drivers to handle a lot of power as long as the enclosure is “truly sealed.” That can be challenging to achieve and relative light due to their compact natures. Some car stereo shops allow for some leakage to minimize cone damage in high-powered systems.

If you like Miami-style 2 Live Crew or Trick Daddy boomy bass, consider a ported subwoofer enclosure for your car. While slightly larger than a sealed box (often about 1.4 – 1.75 times larger),  a Porte enclosure can provide a considerable amount of bass with moderate power when adequately designed and tuned. The design consists of a standard chamber enclosure with a port tuned to allow the waves from the speaker’s rear to get added to the form of the speaker 180 degrees out of phase. This type of acoustic coupling provides for as much as 40% improved efficiency over a sealed enclosure. The added efficiency comes at a cost. Ported enclosures allow excessive cone travel below the tuning frequency of the box, resulting in speaker damage or failure. Consider this type of enclosure for an SUV or hatchback, with the speakers facing back.

While companies like BOSE have proven that the bandpass enclosure can challenge the sealed and ported designs, they can also be the most challenging to build and design if you are trying to get it right! At its most simple design, a bandpass subwoofer box consists of a front and rear chamber with at least one port to the outside. Both can also be ported to the outside as well as within. There are at least a dozen variations, but before building or selling bandpass enclosures, know that companies like BOSE patent some designs. Unlike ported and sealed enclosures, where you can wink and guess the size, tunning bandpass design requires precise dimensions and calculation. The objective of the bandpass design is to give you the sound of the ported enclosure with the sealed type’s low distortion and power handling. Due to size, weight, and complexity, it is not the best choice for a car!