hi chaps,
Ive been lurking on the forum as a viewer for the last couple of years, thought I should post something at last.
I built a subwoofer for my main system around 2 years ago. I have many far more capable boxes lying around here (used to work in pro audio) but, at the time, the wife acceptance factor was important.
The box was built to fit beneath my (quite large) coffee table. Its a tapped horn fitted with a 12" Ciare PW324, a 20+ year old driver with no available ts parameters, although I did measure its resonance at 28hz and interpreted it as having a lowish qs. Since there were no ts parameters it was pretty much impossible to actually design a box, and consequently, the results were more luck than judgement with the expectation of having to apply eq quite liberally.
the project is semi-documented here:
https://forum.speakerplans.com/guesstimates-for-home-sub-enclosure-size_topic102969_page1.html
the results were far better than expected and although the response was rippled, requiring 4db or so boosts at 35 and 70hz, along with a hefty cut at 100hz (despite a 90hz xover centre) its final response is fairly flat to 30hz and the entire system comfortably tops 100db (actual listening levels are considerably lower) in my 5x3.5x2.3m sitting room.
It was originally powered by a bridged technics se9060 but, while that awaits a service and recap, is currently powered by a (bodge) bridged samson servo170. Unsurprisingly, the samson doesnt control the driver as well as the technics used to and the response is slightly boomier but still pretty musical and pleasing.
I also built a 1.7m tall and very skinny powered 8" 30hz relex sub (it fits a dead space beside my refrigerator) for my kitchen radio (pair of eaw sms4).
Anyway, great forum chaps, its really helped me with my journey from 2.0 with one hafler wired surround to my current 7.1 system and with eyes/ears on an upgrade to atmos