Bandpass boxes are compound systems in that they have at least two enclosures: one on the front and one on the rear of the driver. The enclosure on the front, which looks remarkably like a vented box (because it is), acts as a low pass filter and can couple the output of the woofer more efficiently to the outside. They have several useful advantages. For example, the front enclosure can be used as a very effective acoustic crossover, filtering out mechanical noises generated by the woofer, something no electronic crossover can do. For very low frequencies, such an acoustic crossover can be far less expensive and more easily designed than an equivalent electronic crossover. They are called "Bandpass" because the combination of the rear enclosure and the driver form the high pass portion, while the front enclosure forms the low pass section. Making the bandwidth of the system narrower raises the efficiency of the system.

Click below for a selection of empty bandpass boxes.

To determine which type of enclosure is best for your purposes, and for a deeper understanding of all types of woofer boxes and how to build them, take a few moments to study the information on the Enclosures page of our Technical Advice and Assistance section.