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You may have missed it but we are seeing "real world" documented COB grows in the 2 gpw range these days @ 700 PPFD. Even my half assed grow turned out 1.48gpw in 56 days, in soil, 750 PPFD. same ladies, same soil (literally), same tents. Not a bad improvement from .57gpw from my half assed 600W...

I think you are correct about this and I thank you for sorting me out I really do not want to be spreading misinformation. The 1.78umol/s/W does seem to include the reflector losses (from 2.07umol/s/W down to 1.785 = 15% loss). Beta Test Team referred to a study that claimed the Gavita reflector...

Because it is available in cut lengths, this could be a great option for active cooling. Any idea the price a 1 meter?

True, it would depend on how close you pack the 600s. I used to run a pair of generic 600s over a 4X5 canopy, approx 730 PPFD initial. If you put a 1000W DE over a 5X5, approx 600 PPFD. If you put that same light over a 4X4 you get 950 PPFD. So intensity can definitely affect density, but on...

One way to compare each build, use efficiency as a measure of performance and evaluate each build by $/PAR W with drivers/reflectors/heatsink cost included. Then just pick your favorite, scale it up to cover your space at your target PPFD. These prices assume HLG-185H-C A version drivers...

Yes I think the 4.9" or 5.88" are ideal for passive cooling. The 5.375" has slightly less fin spacing and slightly taller fins.

Copper conducts heat significantly better than aluminum, but it cost more. So when you look at it with cost in mind, you could have more mass and more surface area for the same price by using aluminum, therefore aluminum outperforms copper in practice. So it makes sense to use copper...

Yes I think the 4.9" or 5.8" are more passive-friendly than the 5.375" because of its slightly smaller fin spacing and slightly taller fins. The 5.88" is cheapest. Updated these hopefully slightly easier to use, each is shown in 6" length

All that said, for places in the world where sourcing ideal heatsinks is a challenge, a good option might be to use CPU coolers. Their cooling performance is top notch and if you pack a lot of power onto one CPU cooler, the cooling can be very efficient and cost very little.

The widest profile MF35 might be the best for passive cooling because it will have the most openings. Fin spacing and base thickness are good, but the fin height might be taller than ideal for passive. It looks like these are not available at custom cut lengths? If so maximum length is 151.5mm...

I have never grown with more than a 600 HPS although I have seen many of my friends grows that 1000W air cooled and we have run the same cuttings. In my experience the bud density is higher under COB due to potentially higher PPFD and lower canopy temps. This also results in a quicker finish...

That sounds like an awesome lineup !

I used to run these XTEs in flower. If you look at the .7A current row, the cost/PAR W is $3.08 and efficiency is 34%. To compare that with modern COBs, the CXB3590 @ $3/PAR W is estimated 64% efficient, amazing difference.

Important points you raise. The reason I suggest 2000W HPS in a 4X8 is to make the point, to match the yield of 1000W CREE COB, that is what it would take to get the job done. This is how I figured the waste heat for a pair of Gavita 1000W DE: 2105W power draw, 105W ballast heat 2000W bulb...

I have seen the generic 100W COBs for as little as $4 ea but then again Vero10 is only $4. I would like to test a generic 100W COB and see how it stacks up (correction factor will be a fudge factor but I'll give it +5% for warm white.) There are some unexpected cost increases when running LEDs...