i dont know others reasons but multiple light sources give better coverage ive gotten better results from two smaller lights than 1 bigger one, i have a 400w hps but i get better results from using a 175mh and a 150 hps wich only adds up to 325w. 75 watts less and better results and im not sure but i think its because the light energy is being emitted from two different sources not really sure as i have no scientific data to prove it but trial and error have been my best teachers
I have a hard time reading you, but God damn it, you make me THINK every time I do. Much respect.
What color temp MH do you use? How blue have you gone with the MH bulbs? And, do you use that MH/HPS combo all through veg and flower?
I absolutely must agree with you and frosted that light
spread and coverage are a big part of this equation. Until you start pushing major wattage you really *do* need some spread (multiple sources), at least this has been my experience using fluoros/CFLs.
However, since you're talking about mixing spectra here, I think that's worth some consideration as well. I've done one flowering run mixing MH (4000K, if I recall, but I can't say for sure) with HPS, and didn't think there was an appreciable difference. Plus, I was overdriving them both, and while the HPS took it just fine, I burned out the MH pretty quickly @ 3mos
total life. I use fluoros/CFLs, all standard household bulbs, for vegging.