Okay, I know this thread's old and I don't care!
Like I thought, the cool tube is not connected to any ducting. Seems that this design is defeating the purpose and wasting lumens by putting the bulb in a cool tube. The fan sucks hot air and odor through the scrubber and out the side of the cab. This should be fine because warn air is thinner than cool air, right? There is an added PC Fan on the outside of the box to boost the exhaust, I assume. There is no way one PC fan is exhausting an HID cool tube if ducting was connected to one of the PC fan's on the outside of the box, I already tried it with a 400w HPS!
The only difference between this and my cab is that my exhaust hole is on the top (chimney-like) and if I set up the same way there will be an elbox (pvc or ducting) to bend the air upward as it travels out the cab. If inside my cab is 14" x 34" x 42.5" (L x W x H), how many CFM's is necessary to accomplish a design like this? Somewhere in these threads I read that a scrubber reduces the CFM's by 30% if you are pulling air though it.
Also, I would use a batwing reflector instead of a cool tube for maximum lighting.
Thanks in advance!