DIY Tempest Subwoofer 

My DIY subwoofer is based on the SBB4 (super boom box 4th-order) alignment with an Adire Audio Tempest driver.  This driver is very popular with DIYers mostly due to its high performance and affordability.  The driver itself is a 15" monster with about 17mm of excursion both ways.  Total displacement (air moving power) is about 2.5L.  For the uninitiated, that means the driver has the capability to hit those low notes (20hz and below) that lesser subs won't touch.

The SBB4 is a 194 liter net volume enclosure.  It is basically a 24" cube on 4" legs.  This is actually the smallest ported enclosure recommend by Adire.  If a smaller enclosure is needed, a sealed box will accomplish this at the expense of extension.  The SBB4 has lots of mid-bass muscle but also extends to about 16hz in my room.  The enclosure has two 3" ports tuned to 18hz.

The subwoofer is really meant more for home theater but it can do well with music when properly configured.  Drums now sound lifelike and have great impact.  Movies are totally different when you have a sub that extends into frequencies deeper than you can hear.

Here is a picture of the sub.  Sadly I didn't document the build process.  You probably noticed the subwoofer isn't finished yet.  I plan to paint it with black textured paint.: