Now to test the Verticool III:
Here I add 1/8" of McMaster neoprene rubber, Shore 30A with adhesive backing, to the front panel. No air or sound leaks!
This is the new chassis with the Verticool III ready for testing. I'm using a Sunbeam Rheostat and a digital multimeter to measure fan voltage (the $5 DMM has been modified so that its test leads plug into a fan Y-splitter for a positive hands-off connection):
I'm using my highest-RPM 220mm fan this time for testing. It starts somewhere between 3.00 and 3.20V, can't tell exactly because I can't resolve that spot on the Rheostat voltage adjustment. So 3.80V is the lowest I was comfortable using, and I ran all tests at that voltage on the big fan - ~300RPM. (The fan runs at 554RPM at 7.38V.)
The PSI Solo 604 on the left is my #1 computer, the one I don't experiment with. The new unit is on the right:
The fan mounted inside the V III is the SilenX 92mm "11dBA" fan, which runs at 1300RPM at 12V. First I made sure everything was working. Setting the 92mm fan voltage to zero, the AMD Sempron 2800+ die measured 29.2C over ambient. With no duct (yet), turning the big fan temporarily all the way up to 6.4V didn't improve the die temp much, so back to 3.80V. At 5.00V on the 92mm fan it ran, and the die rise over ambient dropped to 21.3C - a 7.9C improvement. At 7.00V I got 19.1C delta T, and 17.0C delta at 9.00V.
At this point you have to remember the rubber is blocking sound from passing thru the front of the case. So a slow fan running on the HSF is a lot quieter on this case than on yours, if you depend on airflow thru the front panel to cool your HDDs.
What I learned from this exercise is that the case is quieter using a mix of area cooling with the 220mm fan and spot cooling with the 92mm fan on the HSF and the 100mm fan between the two HDDs than if I tried to use the big fan to cool everything. It wasn't even close.
The AMD 2800+ doesn't run much hotter when I test with BurnK7. So any voltage on the 92mm fan that's comfortably over the minimum start voltage cools just fine - and at that level the fan is very quiet inside the case, and no noise escapes thru the front panel. With the computer sitting on the left of my monitor, it would be silent at 3AM just like the one I'm using now, which is the same except I'm using a Freezer 64 Pro HSF modded to use the 100mm Scythe fan, turning 550RPM. (The SilenX does not have a tach signal.)
The big fan is suspended on both units. My maximum ambient, hottest hour on the hottest day, was just under 30C last summer.
Personally, I think the two HSFs are a wash. I'd need a very low-noise test facility and expensive test gear to confirm my opinion! (I don't think a duct will improve things much based on some previous testing.)