One for the audiophiles and DIY junkies, an article from Hardware Analysis on how to make your own 10" subwoofer.
Fortunately the workings of a (sub)woofer are extensively documented, both mathematical as well as practical, which gives us plenty of background information to calculate and evaluate performance and frequency range prior to actual construction. The starting point of these calculations is the specifications of the woofer, which usually are supplied by the manufacturer. All that we have to do is to set a few realistic design requirements based on which we’ll then select a suitable woofer and calculate the enclosure and filter accordingly. In the following pages we’ll discuss how to properly select a suitable woofer, enclosure and filter as well as how to go about constructing an audiophile subwoofer that’s both accurate and precise, but also has a high, linear sound pressure level throughout its frequency range.
[The how-to]