Question for Black Ice Pro (1,2,or3) radiator owners
 

Have any of you added a shroud? The 1/4" plenum built into the thing looks barely adequate. If you have, was there a measureable improvement in dT or sound quality/volume?

yes, barely, no change
the major effect comes from lifting the fan off the rad face, ~ 1/4" seems to suffice
a 2" deep shroud would be more helpful, but not so practical in most installations

yah i made a 2 inch shroud for my 120 dual. it helped by about 1-2 degrees or so...

more temp benefit on push side
 

I've tried spacing fans away from BIPs (single 120).
Using MBM diode ratings - same temps shown when shrouding pull side, 1C lower when on push side.
If you're looking to reduce noise, fan on the pull side only (with air pulling into case), it seems that you can reduce fan noise slightly, particularly if you line the shroud with something noise-absorbtive in the high frequency range.
Of course, I could also have simply persuaded myself that it was a bit quieter this way - I don't have equipment to measure low levels of noise and, given that I was installing/uninstalling a fan+shroud inside a case, it wasn't possible for me to do a "blind" A/B test.