captainmorgan: It's pretty narrow band, you're right captain. It has very little Green/Yellow/Orange, but it does have "full spectrum" coverage, if that means anything to you, it just focuses HEAVILY on Red/Blue. The X5 spectrum looked really cool, but I guess they don't support it anymore. NASA wanted their research back? Not exactly sure what happened there.
PICO: This is an RQE chart stardustsailor posted a while back. I believe they used cannabis leaves for the test, but it might just be a typical land-based plant.
The test was performed by shining various wavelengths of light at a plant leaf and recording the percentage of light that was reflected back. So, according to my understanding, the remaining percentage of light was actually absorbed by the leaf and is deemed "useful" for photosynthesis. As you can see efficiency peaks in the 575-645nm range.
As for "light coupling" and speaker design, it's hard to compare. Different frequencies of sound waves take on different forms. Bass expands spherically. It fills the room in all directions rather evenly. As frequency increases, however, the waves become much more directional. This is why, say with a planar magnetic midrange/tweeter, the diaphragm width usually dictates what frequency you have to set the crossover at before beaming sets in. In lighting terms, this is semi-analogous to the beam angle of the light. With these Illumitex light sources you have a very tight beam angle with a very sharp cutoff, yet you use many of them correctly spaced apart in order to achieve a homogeneous light region. I'd say this is similar to a line array. So, what we're talking about here is not necessarily coupling a single spot in the room with the speaker setup and taking FR measurements. Rather, we're trying to create a room where many people can sit and listen/enjoy the music at very a reasonable fidelity. I hope that makes sense and is "correct."