So, my new JBOD has 3 80x80x38 fans mid-chassis. Run either at 7000RPM (full) or 3600RPM (optimum). The former is jet plane annoying. The latter is just loud enough to be irritating (my lab is in a corner of the family room downstairs.) I got a couple of noctua fans, but they don't fit in the SM hotplug carriers (the carrier has a solid thumb-sized depression that protrudes down between the front and back parts of the fan. It's wide enough that an 80x80x25 fan won't fit I could not for the life of me find any low-noise 80x80x38 fans. I ended up getting a noctua na-fc1, which has a dial allowing 0-100% speed, as well as a 3:1 fanout cable. I found that 2500RPM is just about perfect, and the temp fluctuates between 1-2 centigrade higher (never gets higher than 36C).