Would love to see how the base turns out, that look pretty complex to pull off.
What's the reasoning behind the angled woolfer at the bottom?
I'm not speaker builder, but I always thought the glue up was an issue. Something about it not holding up to the vibrations, might be worth looking into.
http://www.trueaudio.com/st_spcs1.htm
To make a long story short:
Depending on the size of the baffle, a driver on that baffle will radiate sound power in 3 bands; one band is where the driver radiates sound power omnidirectionally, one band where the driver radiates sound power only into half-space (half of full-space/omni), and one band where there is a gradual transition from omni to half-space.
One of the design goals for this speaker was to ensure that power response was as constant as possible*, and as uniform half-space is easier to achieve than uniform full-space, all the drivers had to be radiating only into half-space (crossovers help with this). The baffle was then sized large enough such that the uppermost drivers would fire into half-space in their passbands, while the woofer below, as it already fires into half-space because of the nearby floor boundary, needed to go around the baffle to maintain the same power response. It isn't perfect, but much better than most designs.
The reason for the angle is because I can't fit the woofer on the front without making a mess of the large radii. If I could front-mount it and have it look good, I would do that. Conversely, down-firing the woofer might work, but there is an acoustic low-pass filter that is created when you do that, and as the woofer works up to ~200-250 Hz, I don't know how that would affect the woofer's passband.
*doing so tends to provide better imaging and soundstage