In March 2003, we presented the "Little Dynamite" subwoofer - an easy-to-build design that used a single 10-inch driver in a 25-litre ported enclosure. At the time, we said that we'd later be describing a larger, higher-powered subwoofer and this is it.

This new subwoofer is a flow-on from the previous design, where many different enclosure variations were modelled using BassBox speaker design software. It uses not one but two 10-inch Jaycar drivers, two 25-litre pre-built sealed enclosures and two ports. The two 25-litre enclosures are combined to make one unit with a capacity of 37 litres and we'll look at just how this is done shortly.

The resulting enclosure is longer than before and this has allowed us to use longer ports. This, in turn, has allowed the box to be tuned to a lower frequency which benefits the bottom-end response. In addition, the use of two drivers increases the sensitivity and power handling of the finished subwoofer.

Another benefit of the new design is that if you built the previous unit and want to upgrade, you can do so without starting all over again.