This is a guide on how to build a DIY subwoofer to complement your home cinema/stereo system. With a bit of time and effort, you can build some awesome stuff!
HiVi SP10 DIY Subwoofer Enclosure Drawing
Construction of the Peerless XLS10 Subwoofer Enclosure.
DIY Subwoofer :)
The V.B.S.S. DIY subwoofer design thread - AVS Forum | Home Theater Discussions And Reviews
Various subwoofer designs
Make a stylish speaker bar from scratch.
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BeoLab 5 from the inside out!