I set out to build this subwoofer to complete my daughter's 5.1 home theater system, which utilizes two TL variants of the popular Tritrix design for the front speakers, and the vented variant for center, and rear surrounds. I began while in the middle of building the 5.1 system for my daughter, and a pair of the Tritrix TLs for my son. That build is documented elsewhere in the Gallery forum -- the link may be found below with my signature.

Following the same logic as when I selected the Tritrix design, I first looked for a proven subwoofer design, believing that to be the surest path to a good sounding speaker. I was surprised to learn that subwoofer design wasn't nearly as exacting as a full-range speaker, and that I could expect a very good result by simply building a 3 cubic foot box, and using a 4" vent, with a 12" woofer. After looking around for a while, and asking for suggestions in the tech talk forum, one of the regulars, Chris Roemer, suggested that I go with the SA100 plate amp and the Dayton SD315-88 12" dual voice coil subwoofer (since replaced by the SD315A-88, which is in all important respects the same driver without shielding). His advice, I believe, was based on the fact that I wasn't striving for the world's best subwoofer, and that the point of diminishing returns wasn't far beyond the cost of the recommended components. The SA 100 was on sale at the time, and after paying the regular price for the subwoofer, I had all the necessary parts for about $140. The driver is here, and the plate amp is here.

I decided to make this a learning experience so I entered the TS parameters in WinISD and came up with a recommended 2.439 cubic foot box, tuned to 30 Hz with a 4" vent, cut to just under 12" in length. Next, I used Boxnotes to determine the optimal dimensions and elected to follow the recommended structural features, such as a double thickness baffle, shelf brace, and strategic placement of seams (by strategic I mean sizing the various panels so as to minimize the number of visible seams, in the event the dreaded MDF shrinkage occurs). Boxnotes calculates volume occupied by the driver, vent and brace, and recalculates the box tuning based on the area lost. Being a little concerned that most of the builders that responded to my questions predicted a box volume around 3 cubic feet, whereas WinISD recommended 2.4 cubic feet, I thought it would be wise to also factor in the area occupied by the plate amp. I produced the following drawing using metric dimensions for reasons that escape me at the moment -- I think it was because I drew the driver to scale and all dimensions were given by the manufacturer in mm. My early CAD program won't allow you to use both metric and Imperial units in the same drawing.

The shelf brace, shown as the cross-hatched area in the drawing, is cut from a single piece of MDF and resides in dados cut into the front, sides, and back. I elected to place the vent opening in the front, since I guessed that the subwoofer might well end up placed against a wall, or inside a cabinet -- as it turned out, that's where it ended up. I'll add more details tomorrow.

I can post a drawing showing dimensions in inches, if anyone is interested.

Those with sharp eyes, assuming anyone is reading this post, will notice that the vent is shown too high in the side view. I probably moved it when I drew the driver, and forgot to move it back into the correct position (which would have sullied my purdy drawing).