Rather simple thing ... well not so much anymore as last week the LED Phanteks fans were $17 w/ a $10 rebate on newegg. This week the non-LED ones are $10 after $5 rebate.
It's a given that the adapters will add to the noise profile so this way you would be able to put a 140 on a 140 and a 120 on a 120 both non PWM. and compare yaself..... PWM fans of course can have some added noise as well but reviews indicate it's not bad at all on teh Phnateks XP. I'd offer to buy it off ya if ya didn't like it but as shipping is more than the fan ....
As for the rad surface area....
140s in your example are 215,600 sq.mm.
120s in your example are 216,000 sq.mm.
..... but ya get some of that back (theoretically) as less dead area behind the fan motor on the 140s as ya have 8 less fans.
If cost is a consideration.....
140m rads = 3 * $85 + $66 = $321 + $175 for fans = $496
120m rads = 3 * $105 + $80 = $395 + $315 = $710
So it's a $214 decision (43% More)
Other things to consider.....
Are we talking 1850 rpm versus 1200 rpm.....? That is going to be what as far as controlled range ?
I can confirm 250 - 1277 rpm on Phanteks Non PWM
Maybe lowfat can chime in on the APs range
Also with 15 versus 12 fans soundwise .... if we assume that both fans have a base sound of 24BA.
15 Fans would have a Sound Pressure Level (dB) : 47.5
12 Fans would have a Sound Pressure Level (dB) : 45.6
So the 120s would have to be 1.9 dBA quieter from the getgo to match the sound with all running
Another way to put it ....
With one fan at 24.0 dBA, 15 Fans would have a Sound Pressure Level (dB) : 47.5
With one fan at 25.9 dBA, 12 Fans would have a Sound Pressure Level (dB) : 47.5
Can do the math yaself here
Also, the Phanteks PCBs should be out by end of month meaning ya can take ya CPU_OPT header to a 5 way PWM cable splitter..... run each of those to a Phanteks Fan PCB and have PWM control over every one of ya non-PW 3-pin rad
(up to 55) fans.
Splitter => PCB 1 => 6 or 8 rad fans on 420/480
Splitter => PCB 2 => 6 or 8 rad fans on 420/480
Splitter => PCB 3 => 6 or 8 rad fans on 420/480
Splitter => PCB 4 => 4 or 6 rad fans on 280/360
Splitter => PCB 5 => up to 11 case fans
You can also use up to 8 Phanteks fans on the PCBs when connected to a voltage control MoBo header.Edited by JackNaylorPE - 3/3/14 at 7:16pm