The T3S Kit by Javad Shadzi
Javad posted the Thompson 3-way project on FaceBook., which is a bigger more ambitious speaker system, but when I did the surrounds for that system I was shocked by how good they turned out, the response is truly ruler flat, distortion is low and they sound really good. It struck me that this is a remarkable and simple design for under $200 that virtually anyone can build, in many cases with scrap materials in your lumber collection.
These are about 5 liters, external dimensions are 11.5″ tall, 8″ wide and 6″ deep, with this size they come out to a Q of .9 as measured, and are flat to 70hz where they roll off below that at a typical sealed 2nd order 12dB/octave rate. This means they hit quite low bass notes even below 50hz with good audibility. Considering their size, this is a nice result and compromise. These can be made bigger, feel free to model, they can be made deeper up to 10-12 liters to extend bass even more, but be sure to keep the baffle dimensions the same.
The tweeter is centered on the baffle 2-3/4″ from the top, the woofer center is 8″ from the top, both drivers are centered on the baffle laterally. Hold these dimensions precisely from the top.
For the circle jig settings: