I think that Mammoth's point for suggesting to put an LED puck in a reflector with it pointed away from the tank was to help eliminate hotspots. While I may not be a fan of his particular design/idea (mainly pointing the LED's away from the tank), I do think that we can reap some benefits by mounting the LED array inside of a nice reflector.
If you like a MH bulb in a reflector, 60% of the light is going straight down into the tank, the only reason we use reflectors is to capture and use the rest of that wasted light that does up away from the bulb. it isnt to spread the light. The light already spreads fine from a MH bulb in a nice sphere.
if you want a different spread then what the LED gives, using a small lens to bend the light slightly is a much better idea then trying to direct the light away from the tank and bounce if off different facits, thats why we use optics instead of reflectors.
We actually do use reflectors on MH's to spread and distribute the light more evenly. It's not the sole purpose; like you said, a big reason reflectors are used is to help utilize the wasted light, going away from the tank. The two ideas of utilizing wasted light and spreading that wasted light go together. A good reflector points the 'wasted' light back into the tank, trying to focus it into areas other than the hotspot produced by the front of the bulb.
Mammoth, keep in mind the law of reflection which is that the angle of reflection equals the angle of incidence. Thus a tight beam of light, such a from an led with no lens will bounce off the mirror like reflector in that same exact tight shape. You would not spread the light, just change its direction. Think of a laser bouncing off a mirror...
LED's don't emit light at one particular angle; they're not really focused. When bounced off the same reflector, light coming from the outer part of the arc will bounce at a different angle than light emitted further inside the LED's arc. Your argument would work if all the light rays from the LED were parallel with one another, but they're not. If they were, you'd have something acting similar to a laser. Also, reflecting adds distance; while that takes a toll on intensity, the area under the viewing angle blows up.
The main point of my long post:
LED's have an incredible amount of potential, but they pose some challenges.
Consider a single LED. Let's say it has a viewing angle of 140 degrees. I'd say that's a pretty good spread. But, because of the wide angle, a good portion of that light will spill over the sides of the tank, never reaching the animals it was intended for. So, we focus it with a lense or optic. Now the light is more focused; it's much more efficient, since we're minimizing the wasted light. Because we're not wasting as much light, this LED now has a much more potent 'punch' for penetrating, making it a more viable option for growing light thirsty animals.
Now, let's add more LED's to create a wider spread of light, so that we can grow corals in any area of our tank. That's a great idea. If single LED's were full spectrum, we could stop right there. The fixture would be done. But, LED's tend to emit pretty specific wavelengths. That's why we add LED's with different wavelengths, to try to achieve a full spectrum light. Again, that's a great idea.
BUT, if each LED has it's own optic, then we start to get color banding/uneven distribution of color. We also still have small hotspots. Uneven color distribution is my biggest complaint about LED's.
Color distribution and overall spread is my biggest problem with most LED fixtures. I think quite a few of the fixtures are great (Like the Radion, Hydra, Vega, and other full spectrum fixtures that cluster the LED's), but they could be better. If they take measures to alleviate color banding, then they also sacrifice some of the overall light spread.
If we place a cluster of LED's, with a full spectrum, into the a reflector, similar to a Lumenbright, we should see a better mixing of color and more even distribution of overall light. The only issue that's not solved is the hotspot; with LED's, there's not 'wasted' light on the back of the emitter that we can utilize to add intensity around the cluster's hotspot. With that in mind, I've been playing around with the idea of using a diffuser to bounce some of the central light back into the reflector, distributing it more evenly. This will soften the hotspot and add intensity to the area around the hotspot, bringing us closer to a more even PAR reading throughout the lighted footprint.
Disclaimer: This is all my opinion. I don't want to make people angry. I may disagree with you, but I could easily be wrong about the topic.
