I had for a couple of years wanted to rehab the downstairs living room into a dedicated HT room and office. I wanted pretty big sound, yet needed to balance my lack of a working shop space, limited wood-working skills, and some other factors (like budget, dratted money thing!). Also, given the time constraints I face trying to finish up the Physical Therapy program at ISU, I was leery of a complicated build, or multiple small builds.
I had previously owned a B&C 21SW115 and had it in a QB3 alignment. In spite of being poorly aspirated (I'd not yet learned about the poor performance of very low aspect, undersized slot ports), it being a pretty formidable driver & I loved the thing. I had always wanted to try it in a horn, and alas that never happened. SO, few years later and I get the itch.
There is no way to build a large horn and then move it downstairs. I went so far as to build a full-size cardboard mockup of a lilwrecker, and it would not fit around the corner at the top of the stairs. Well, it's going to be a dedicated man-cave down there, so why not build it in place, size not an issue (up to a point).
B&C came out with the DS model of the 115, and I'd played around with modeling it. What would it do in a suitable horn? Inspired by the simplicity of a single fold 15" TH I'd run on to here at AVS, I played around with fattening the cross sections up and the initial results looked promising. I bounced the idea off of lilmike, and he took it from there with simplicity and performance the goals. Loud, low ... not small, noooooo, that it is not, and I'll have to saw it up if/when I leave here. I have no problem with that.
Acceptable to me
It models around 98dB on a watt, ho-hums at a kilowatt, and has an F3 of ~20hz. Not world class, but no
....but here are a few build pic's.