@BOBBY_G If you have to compare at Tj=39 to make the PCT say what you want, there is something seriously wrong with the PCT. Now I know that
@SupraSPL says that it's because Tj is actually mislabeled, and is Tc, which if it's true means Cree has pretty terrible thermal resistance, plus they don't report current droop right, plus they under report lumens, not to mention they don't fix bugs.
This is why we need integrating sphere testing.
By the way, your 166lm/W @ 85C was spot on, but sort of pure luck. It's 2712lm/16.3W/32.6V. Eyeballing charts is just impossible.
Anyway, fuck that noise. The PCT is untrustworthy, or Supra is. If we can agree that the SupraSPL datasheet is correct, and Citizen's simulator is correct, it gets really easy to compare. And sort of fun.
For instance if you run 2x CLU048-1212, you get about 155lm/W at 6568 lumens. The exact same 13137 lumen output as a single CXB3590 at 2.4A, for $25. If you use a monolithic heatsink, the costs for cooling are identical, and I would argue in this case the cost to cool one cob at 87W is about the same as two cobs at 42W. Heatsinks just scale up with weight, basically.
At 500ma, I have no idea, you are probably right. I just thought the numbers were a little wonky. As in, not agreeing with the PCT at Tj=85C, or Supra's spreadsheets, or the Citizen datasheets.
But lets look at it at 50C, which is an easy number to hit at 500ma. CLU048-1212 makes 175lm/W at 500ma. Cree makes ummm...178lm/W at 1.5ma drawing a straight line between 1.4ma and 2.1ma. Equal costs, same efficiency (Citizen slightly ahead in umol/J), 3x the spread. You are probably right if you did individual heatsinks the Citizen solution would cost more, but probably not much. An extruded solution like heatsinkusa would cost the same regardless of number of cobs. Labor is higher, but people love that spread, yo.
This is way too long. But it was fun to do the math. At higher Cree currents, a couple $12 Citizens pull ahead. That's pretty cool. And it's a horse race at 500ma vs 1.5A.
For everybody's future reference here is the Supra spreadsheet:
https://docs.google.com/spreadsheets/d/1nKfc12OCuDu7puJCa_6maefyCVm3gS5sBmzAXOlh06w/edit#gid=1157681753
And the Citizen simulator:
http://ce.citizen.co.jp/lighting_led/dl_data/sim/CITILED_ver5_Selection_Tool_WEB.xlsx