I've been wanting to get started on something like this, but I don't have the wood shops available that I did to me any longer. I thought I'd pass on the concept and see if maybe some people on the forum would be into it. I know Danny is rather busy, too, so it may be up to us for a moment to expand on some possible projects.
What I've been wanting to do is make a capable speaker that is a WAW, woofer assisted wideband. Maybe that's the right acronym, I'm not even sure! The point is to use a fullrange driver with a bass driver.
What I'm proposing to do differently is use Bipole drivers for bass because of how they act. Even small drivers in bipole can produce powerful bass, surprising bass. I've heard 4" drivers absolutely pound before in Bipole. What is unique is that is doesn't have baffle step loss because both drivers are opposite firing in phase. What also is unique is the vibrations for the cabinet cancel really well - spikes and such don't do a lot for them so you can just use some felt pads or extend the base in some fun way with woof. The bass spreads well in a room.
The other component is I want to really make it sound surprisingly natural. So The fullrange will use an aperiodic vent. The bass drivers will sound very natural also with aperiodic vent, but they could also be converted to a transmission line if someone is skilled enough. A TL line will put out very impressive low bass.
Now onto what it looks like. I drew a simple box to show you. I would line the midrange with no-rez and stuff it decently. The stuffing is good because in this case the driver can use extra dampening. The ape vent should help keep the resonance of the internal chamber down to keep the sound natural. The bass with the ape vent will be very natural sounding.
The reason the bass drivers (M165) are side firing is that the LGK needs as narrow of a baffle as it can get. At this point the narrowest is approximately 6". All edges should be rounded over, and felt would be pretty trick in a patch around the LGK. The LGK could be offset to one side some.
The crossover isn't completely decided yet. But it's looking at Danny's baffle compensation should work (I took a guess at the values), along with a 60mf Solen bypassed by a 6uf Gen1 Sonicap in series with the LGK & BSC - and my own little change following that. The M165's will need a 2nd order around 300hz. Keeping the LGK slope a little more gentle is intentional because the M165's should be setup to be on a 3 way switch to adjust for bass. As is at 89.9db they will be too sensitive for the nominal w/ BSC 85db LGK, so the M165s will have to be attenuated down to 85db, but in small rooms the gain may still be too much. For that reason a switch could be used to drop it down -3 and -6db. The details aren't fully settled on that, yet. I'm not certain if a 300hz first order will roll the LGK off better than in simulation yet or not, for example.
The FR response I'm seeing has a little bit of a dip at 4khz, but is actually surprisingly smooth otherwise. It looks like the baffle size at 6" wide may smooth the higher end of the LGK. Granted it may be a minor blurring, but that may not be a problem at all for the type of listener who wants smooth, natural sound, with expensive sounding bass.
Right now It's looking like the box would do well at 42" H x 6" W x 12" D w/ a 6" x 6" chamber for LGK on top. This gives around 1 cubic foot for the woofers. With them adjusted to 85db and a touch of room gain, you should be getting appreciable bass into the 40's, if not some into the 30's albeit quieter than a real sub. The LGK would end up about ear level for recliners and such. The ape vents need 4.3" cut outs, so this is right at the max with .75" depth walls.
I thought about placing the M165's towards the bottom but I'm worried too much floor loading won't sound as natural.
Anyways, this project will get my support to work on the electrical side. I suspect that while Danny doesn't have time to build boxes, were someone near him to bring one to measure he might have some say so in crossovers (probably will have some say so period).
Whelp, I guess now we see where this goes, if anywhere...