Also, what do you think about mixing 4000K and 2700K to get a broader spectrum? My original plan is to put 6 COBs per bar with 3 of each per bar. Also, which model of Citi 1818? There's quite a few to choose from on Digikey, but thinking going with the higher lumen per watt?
If you want to do 6 per 4x4 you can bump up the power to 2.1a here is the numbers for that
Citizen.1818C4.3000K 6 COBS @2.1A ON 5.88 PROFILE HEATSINK
16 SQ.FT. CANOPY 93% EFFICIENT DRIVER @10 CENTS PER KWH
Total power watts at the wall: 731.18
Cobs power watts: 680
Total voltage forward: 324
Total lumens: 93840
Total PAR watts assuming 10% loss: 258
Total PPF: 1253.88
PPFD based on canopy area: 843.54
PAR watts per sq.ft.: 16.13
Cob efficiency: 42.14%
Power watts per sq.ft.: 42.5
Voltage forward per cob: 54.0
Lumens per watt: 138.0
Heatsink riser thickness / number of fins / fin's length: 0.27in/14/1.0in
Heatsink area per inch: 260.01 cm^2
Total heat watts: 393
umol/s/W / CRI: 4.86 / 80CRI
Heatsink length passive cooling @120cm^2/heatwatt: 181 inches
Heatsink length active cooling @40cm^2/heatwatt: 60 inches
COB cost dollar per PAR watt: $0.75
Electric cost
@12/12 in 30 days: $26.82
Electric cost @18/6 in 30 days: $39.98
Cost per cob: $32.08
Heatsink cost per inch cut: $1.74
Total cobs cost: $192
Total heatsink passive cooling cost: $315
Total heatsink active cooling cost: $104
As afar as where to get them I would go to cobkits and there is jerry on alibaba also cdi if you want to wait 6 or 8 weeks. If you went with the 1812
northern grow lights has them here is the 1812
Citizen.1812C4.3000K 8 COBS @1.4A ON 5.88 PROFILE HEATSINK
16 SQ.FT. CANOPY 93% EFFICIENT DRIVER @10 CENTS PER KWH
Total power watts at the wall: 651.61
Cobs power watts: 606
Total voltage forward: 433
Total lumens: 86052
Total PAR watts assuming 10% loss: 236
Total PPF: 1146.96
PPFD based on canopy area: 771.61
PAR watts per sq.ft.: 14.75
Cob efficiency: 43.33%
Power watts per sq.ft.: 37.88
Voltage forward per cob: 54.1
Lumens per watt: 142.0
Heatsink riser thickness / number of fins / fin's length: 0.27in/14/1.0in
Heatsink area per inch: 260.01 cm^2
Total heat watts: 343
umol/s/W / CRI: 4.86 / 80CRI
Heatsink length passive cooling @120cm^2/heatwatt: 158 inches
Heatsink length active cooling @40cm^2/heatwatt: 53 inches
COB cost dollar per PAR watt: $0.78
Electric cost
@12/12 in 30 days: $23.96
Electric cost @18/6 in 30 days: $35.69
Cost per cob: $22.93
Heatsink cost per inch cut: $1.74
Total cobs cost: $183
Total heatsink passive cooling cost: $275
Total heatsink active cooling cost: $92