From what I understand, heat from HID lighting + the temperature of the room determines your leaf-surface temperature, which has an optimal range for photosynthesis.
Since you are switching from HID lighting (which radiates infrared heat to the canopy) to LED (little to no infrared heat), my first question is, did you compensate for the loss of infrared heating your canopy by raising your room temperatures?
I believe it was the owner of CA Lightworks who told me the room temperature for LEDs should be between 82-85 F, and to lower the night temperatures a bit more than usual so that the average root zone temperature would stay in the ideal range. (If you have a DWC with a chiller or similar setup I guess you could ignore this since you can dial your root zone temps.)
My second question is what angle reflector are you using and are you using it according to the
Spectrum King Coverage Areas Advice?
Spectrum King 400 Series (and 400+)
- 60° reflector: Covers 4’x4′ area @ 3′ above the canopy for normal plants and should be placed up to 4′ above the canopy for sensitive strains. This reflector is meant for 12′ ceilings or higher and was intended for use on taller plants over 6′.
- 90° reflector: Covers 4’x4′ area @ 18″ above the canopy for normal plants, and should be placed up to 24″ above the canopy during flower for sensitive plants. It can cover an 8’x8′ area in veg @ 5′ above the canopy. The 400+ 90 degree reflector unit is meant for plants 2.5′-6′ tall during flower and is your best choice for ceiings 8′ -11′.
- 120° reflector: Covers 5’x5′ area @ 12″ above the canopy during flower for normal plants and should be placed up to 18″ above the canopy for sensitive strains. It can cover an 8’x8′ area in veg @ 3.5′ above the canopy. The 400+ 120 degree reflector unit is meant for plants 18″-42″ tall during flower and is your best choice for ceilings under 8′ high.
I've been researching Spectrum King for awhile and after speaking with the owner I decided to start saving up to buy this light and test it myself. It seems you can expect between 1 to 1.5 grams per watt with the 400+ although
SK has a YouTube video claiming they pulled 1.8 GPW on their 400 w/ 60 degree reflector.
It seems really hard to do a fair side-by-side with all these lights. I would like to see them do several runs trying to optimize the yield of each light, specifically adjusting their grow style to fit each light's characteristics, or at the very least measure the leaf-surface temperature under each light and keep those temperatures as close as possible. So many variables! For example, those 1150 DE Gavita numbers seem pretty low - more watts, improved spectrum and efficiency over single-ended 1000W HPS and they yielded LESS? I've heard of people using 1000W DEs over a 5' x 5' area and pulling close to 4 lbs...Surely something critical was way off; perhaps they didn't account for the extra heat of the 1150 DE?
Anyway if you look at their numbers, even though they pulled 2 lbs off a 1000W which is slightly greater yield, I would say the combined savings over time on cooling and bulb replacements, plus savings on using half the energy, while still yielding within 4-5 ounces of the 1000W, making it over DOUBLE the grams per watt (not even factoring in the extra cost of cooling 1000W HPS), and also higher quality (better spectrum, allowing full genetic expression of terpine profiles, plus higher THC levels), without a doubt makes the Spectrum King LED a "rival" to 1000W HPS - that's putting it nicely for the HPS, IMO!
