Lower PPFDs in a 4x4
(2) T4-1400 685 PPFD (430 watts)
(2) T3-1750 610 PPFD (405 watts)
(2) T4-1750 830 PPFD (539 watts)
(2) T3-2100 715 PPFD (492 watts)
All the wattage figures are total input including fan/driver loss and PPFD figures account for lens loss. I personally wouldn't dip down as low as 610 PPFD, but that last option at 715 PPFD would only run about $1100. But again the two T3-1750s aren't much more and would blow a 600w HPS out of the water. I do have a 3x3 I'm running at about 500 PPFD but it's just an experiment I've been playing around with to see how it affects yield. 1.1 GPW in soil (CXB 3070 AB) and I'm wanting to try it in hydro too.
I'm working on getting this information on the site. The plan has been to provide graphical charts in each product page but it's getting to be a mess as I imagine someone flipping back and forth between product pages trying to figure it all out so I might end up just pasting the spreadsheet on the front page, every model and every space combination for single and multiple lights in one table starting to look pretty good... would avoid posts like this one