I was going to reply to comment about your led fixture being able to grow if the were cfls… then I got a peek at the new unit and thought, that’s sexy! Then I seen plants pics, and those are sexy too lol.
Alas, final comment was back to boring old lights. You know, it’s not really a simple answer anymore. Most of the cree, bridgelux, citizen, and luminous flagship cobs are in the neighborhood of 200 lumens per watt in cold white at around 50 Watts. Efficacy is lower in warmer white, efficacy is even lower from 70 to 80 to 90 cri. In my opinion, the Cree and citizen 3000k 90 cri have about the best horticulture spectrum. Those are around 130 lumens per watt at 50 Watts. The lumen count not as important, but that’s how they stack up in performance.
Watching a few side by side grows of the 3000k 80 cri vs 3000k 90 cri, yields were about the same. 90 cri had a few more inches of stretch over the entire grow, but finished usually between 6 and 10 days earlier. You know as well as I do, individual results will vary. I can tell you that there’s no need to build to 50 Watts per square foot unless you’re doing something to push the led efficiency low. Someone like yourself is probably capable of pushing plants with light, so maybe 50 Watts per foot is something you would personally be interested in. But I would surely go with dimming driver if that was the case. I can’t speak for them all, but the meanwells adjust the output current rather than load a resistor. So dimming will increase system efficiency pretty much at linear rate. 500 wall watts dimmed to 50% will draw about 250 watts. And you’ll also then see a boost in led efficiency as well.
All said and done, a 50 watt Cree cob with passive sink and meanwell driver is around $85 give or take to build. Citizen about 20 cheaper. The bridgelux cobs don’t have the efficiency loss at higher current, so they’re a little more popular to run in 70-75 watt range for about a US dollar per watt.
As we were discussing in the other thread, the smaller cobs are a good option in some applications and obviously cheaper per cob. But not necessarily always cheaper per watt.
The quantum boards or other mid power pcb boards are also an option. They’re good, not always the best. But they’re super easy to put together, and a lot of people like that. Especially with the high led efficiency.