This light build is for a small area, and I am using some inexpensive Cree CXA2520 and 2540 cobs. I must have gone through 10 sketches/schematics based on different cobs and current options for a small space (2x2 or 2x3). After jumping the gun and ordering some HSUSA heatsinks ([email protected] 21" x 5" and [email protected] 21" x 2"), I've been looking at slightly larger spaces, for which this light will be too small. But I'll deal with that with a new build later. This light will have 12 cobs, 6x CXA2540 at 4000k on a 1-amp circuit, and 6xCXA2520 at 3000k on a .7-amp circuit. On paper, this will give about 230 watts on the 1A circuit, and 120 watts on the .7 A circuit. I plan on upgrading the cobs in each circuit at a later time when today's expensive LED cobs become yesterday's inexpensive LED cobs. I ran a passive heat test at .5, .7, and 1 amp, and after 2 hours of running, only the .5 and .7 amp currents would allow of operation at around 55C or less (thermometer resting on the fins). No doubt the junction temp of the heatsinks at each cob was higher. This was in a room with an ambient temp of 16C. Basically, running passive using HSUSA heatsinks with any decent amount of cobs/current while keeping costs, weight, and bulk down is not really working out well. At 1 amp with some temps in excess of 70C, it was uncomfortable to touch the heatsinks. May have to experiment with passive cooling with some pinned heatsinks later. So I ran temp test with a couple of ill-fitting fans, and temps were well below 50C test level in the Cree spec sheets (26-38C). So active cooling it is. Correct size fans are on order. Next on the list is a framing and wiring conduit system to keep the build somewhat clean looking, but we are coming up on xmas, so I may not be able to complete this this month...ugh. I'll put together an additional strip light with passive cooling after this one is operating (really liking those quantum boards). Enough talk, here are a couple of shots of the parts.