Oh, I mislead you with the Pabst fans. I reread the thread: I wanted to buy the Pabst fans, for the Dual Sonnet CPU, but didn't in the end, since I needed a special torx screwdriver with a nipple in the middle of the star, I delayed this project.
On the noise, yes they differ only in 1dB(A), but small fans with that airflow are almost always loud, so the hope (as also told to me in another forum, back then) is, that newer fans will very likely be quieter, in general.
There was another option I had in mind. Replace it with a thin 80-100mm fan. With double the airflow of the two single Sunon fans (2x13cfm).
Dual CPU Sonnet:
Since the Sunon fan is 10mm thick and the Pabst is 15mm thick and for the Dual Sonnet CPU one would have to move them by a few mm, so that the case closes properly (optical drive cage hits fan's frame, when closing door, otherwise).
I then got the idea, that if one takes a big diameter fan, the thickness can as well be picked higher, but I didn't plan to go over 15mm, because with like 25mm the fan would be moved to far away from where the CPU-chips are. The fan will hang over the cooler. See picture 1: the blue bar is the 100mm mounted on the copper heatsink (orange), overhanging, the red one is the case fan.)
Dual CPU Sonnet END
On your Single Fan Sonnet CPU:
Since you have the single fan Sonnet CPU, it can be as thick as you want. [Edit: I used a price comparison site and it seems there are no 50mm fan thicker as 15mm. If we can believe the paper the
Gelid Solutions Silent 5 (FN-SX05-40) should be interesting, Gelid actually rebrands existing fans, but I didn't find the original for that, maybe this is an own-engineering piece... it has a high air pressure, so that might cause the good specs.]
Also there is a 50x15mm fan by SmartCooler LFM1350T, that has a thermal sensor and is 25dB(A) at 13.8cfm at 50°C (the temperature range it reacts to goes from 25-60°C). Unfortunately it is not widely sold anymore, but maybe, if you look around for a longer time, you will find it on Ebay.
This manufacturer makes several other 50mm fans, even some with 25mm thickness! It is a bit confusing to navigate through the sections, though:
http://smartcooler.de/frsce-AL.htm
They also have complete Mac-Fan sets (I am not sure, how good they are though, also the specs indicate, that they have lower airflow and maybe are only quieter because of this)
http://smartcooler.de/frsce-MACL.htm these sets come with 3-to-2Pin-adapters and stuff.
You also have the 1GHz model. I have the 1,2GHz model and still run it without(!) fan, it is passively cooled by the original stock cooler. The purple Sonnet heatsink, would also have more flesh and be even better. Mind I live in a region where Temperatures inside the house do never rise above 23°C in summers (over the year we have 19-21°C inside the house). Even a weaker 50mm fan might do, if you don't want to rely on just the heatsink.
Other solution for CPU-fan: If, you want to try a fan there and a 50mm fan is too loud for you, you could try to somehow attach a 80-120mm fan under the ODD cage, so that it matches up with the heatsink, when you close the door (see the two drawn picture that show how to route a thread/string or zipties - and see these pictures link where I used tape, just to show the positioning. The ruler represents the L-shaped shield on the case fan
http://s667.photobucket.com/user/Idonthaveaguess/library/Heatsink or casefan mod ).
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For the 120mm noctua fan, it has 90m3/h that is 54cfm, the stock case fan has 146m3/h (86cfm).
I heard people using 100-120m3/h fans (71cfm), but they also used a 80mm fan additionally on the f-bracket (where the airportcard would go). People mentioned a combination of Antec TrueCool or TwoCool 80mm (F-bracket) +120mm (case-fan) fans in this scenario.
Others mentioned the Antec TriCool with 134m3/h (79cfm) to be good and quiet, though on paper it has 30dB(A) which is loud. That might just tell us once more, that on paper doesn't always reflect, what is reality (maybe they are just more honest, or too honest, than other manufacturers).
The main fan doing the cooling job seems to be the fan inside the PSU, anyway, because it soaks up all the heat through it and out of the case.
In the applediscussionsforum a user mentioned successful use of a Akasa Black Fan Series (AK-174BKT-B) (which I planned to test, but they sent me the wrong fan and I didn't buy it again). This fan has the same temperature control attached to the fan itself, like the stock fan. You can see a little green or blue tear next to the motor of the fan.
If you consider an Enermax or Nexus fan, be aware that they will state the beginning noise and not the noise at top speed, so an Enermax Twister Cluster or Silence T.B. with an impressive 11 or 15dB(A) is actually only that quiet at the lowest rpm! (other manufacturers give the noise for the top rpm).
There is a Silenx EFX-12-15T with Thermistor (in this case a cable with a sensor at the end, that you can attach to the ODD cage bottom, so that it is near to the heatsink of the CPU.) The interesting thing is, that picture4 (green frame) shows, that the fan gets speedier at a higher °C than the AKASA, picture5. So it might be quieter for a longer time, according to HDDs in my G4 the internal temperature never rises above 40-45°C.
The Japamac Cooling site, linked to by reddraggon in the noctua thread mentions the Cooler Master Excalibur 120mm (R4-EXBB-20PK-R0). (I would find it interesting to know, if Japamac has tested any other fans, on paper the Excalibur would be loud, too, with the 30dB(A), but the sound as such might be more pleasing.)
What other components do you have in your Mac (hot graphics cards, a lot of drives)?
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the noctua 80mm fan you mention worked great for me.
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