Mark, what you are proposing is not practical. A subwoofer, sure. But a full range, it is not level with your ears. What you need is an enclosure that is high enough for you to get the benefit of those soundwaves that have a shorter wavelength and direction identifiable. The lower wavelengths are long enough that it is impossible for anyone to know where the sound is coming from. That is why a subwoofer can be placed almost anywhere within a room, but full range speakers cannot.
Obviously you are attempting to acheive a radiating effect with the top of the table deflecting the soundwaves in all directions. However, a flat, perpendicular wall is not the answer. You will need to create a horn effect that evenly distributes the soundwaves throughout the listening area.
It just so happens that I am about to begin my next project, working on this very type of enclosure, and it is based on
the Duevel type drivers. I am in the process of starting to build an enlarged type
"Venus" six sided enclosure. I've already made test cuts of 60% for each piece, and put them together, but only in test form. All the parts are gathered and ready to go.
What I am using is the
B20FU20-51FW, and the tiny
ND20FA-6 dome tweater. There are several, like this one, in the group and all are great, small, and easy to work into the project with the minimum crossover. But you will have to get the sound at a higher lever, or you will wasting it's ability to give you good sound.
Let me suggest that you go to the Full range section and read up on the threads that cover the B20, including the Chang threads. Then think about coming up with something like the Duevel type enclosure.
The biggest problem will be to create the top horn, which can only be made with a wood lathe, or potters wheel with clay. I still haven't overcome that hurtle yet, but will before the project is finished.
If you do not have a table saw, or are unable to make a six sided enclosure, you can always go with the other enclosures, such as the Bella Luna or Jupitor variant. Only you will have to only use one horn on top, unless you are really good with a lathe. I'm not, so I wlll go with only one horn, and smooth out the top of it, to make it blend with the enclosure.
Anyway, that is something for you to think about. I will be recording my progress with my project and will put it on the Full range section beginning the end of this week.
Anyway, good luck with your project.
If I find a source of 14" sonotube, I'd seriously consider going the route you mention.