Calcuationg Fan Speeds

[NeverBackDown]

no BFS pros are not silent at 12v (1.5m still audible)
AP123 are quieter than BFS pros, but neither move air like the cougars. with
that said, the cougars are choppy loud at 12v. under-volted 7v they are so-so
performers and still a lil windy in noise.

what are the conditions these are to be used as? case fans or rad/HSF fans?

Rad fans. Do you have expierence with any of these fans? I take it that's how you got these details?

 

[Zoot]

Considering it's less and less power being provided in order to shift the same mass (fan blades) it won't be linear. Also, there's the fact that once the blades have their own momentum, they are able to spin by themselves - ie - they have their own momentum too, which is increased more and more as the voltage increases.
It won't be completely linear, but I have no idea about the maths behind it in order to establish the exact shape of the curve

Well if you want to get into detail, you really have to describe it with a differential equation.

 

[NeverBackDown]

Well if you want to get into detail, you really have to describe it with a differential equation.

I think we settled it by saying it's just doing the math i originally posted but it won't work with every fan... Not every fan is linear.

 

[Zoot]

No fan is linear. It goes for any DC motor, the load on the motor has an adverse affect on the rotational speed, in this case that's the amount of air the thing is moving.

The linearity is just an approximation.

 

[airdeano]

Rad fans. Do you have expierence with any of these fans? I take it that's how you got these details?

i do with all of those fans.
the BFS pro are nice fans, weak pressure fans, under-volt with no adverse
issues or mechanical issues, have LED option, better case fan than rad/HSF fan

the AP123 is an mediocre fan for 12v sound, better pressure over BFS pro
and under-volt well - but not stable or predictable performance in 5v usage.
the AP121 is a far better fan for radiator

cougar has best pressure of the three, but crap bearings, excessive "chop"
noise for noise-level and really doesn't disappear until really low voltage but
then they are useless like the BFS pros at low voltage. in open or case fan
they don't exhibit the choppy noise, so when "restricted" they tend to
reverb. but i couldn't stand the inconsistency of the bearing they used.

 

[NeverBackDown]

So what do you recommend? Cause I guess I can't pick good fans lol
Edit: if undervolted all fans will run at 7volts.

 

[airdeano]

right now i'm trying out the helix 120, sp120 PE/QE (pass on PWM for now),
BGears B-Blaster 120, noise blocker, noctua.

helix 120 (AP-15 clone) is a fine fan, mixed on performance, but deffo under-volt
without AP-15 clicking and grinding. strong and inexpensive.

so far for a nod it is either the sp120, noctua f12, BGears..

the NB option was ok, until the PWM was louder than F12 at same speeds and
under performed by 2°-3°.

so far with open air (no filter) tested, then next is filter performance. i believe
it'll come down to sp120 or f12. which i think it'll be all up to static pressure
at XXXXrpm..

 

[NeverBackDown]

Sp120s are very expensive for a 2pack.. almost 40$! Noctua is not an option as they one of those is more than half of the Sp120s price
Edit: forgot to ask. So they helix fans are also a good choice is what you're saying?

 

[airdeano]

they are a good alternative to using AP-15 and the lesser of the sp/f12 fans.
where are you buying your sp120? newegg 27 shipped..

 

[NeverBackDown]

I want the QE not the HP edition lol
Also i shop at newegg and amazon depending on which is cheaper. I always get free 2 day shipping(doesn't matter what it is or many items) from them so they save me tons of money through that

 

[airdeano]

under-volt the PE 7v.. a tick slower and lot stronger than QE at 12v.

PE - 12v 2350 7v 1370 5v 979
QE - 12v 1450 7v 845 5v 604

 

[vorticalbox]

under-volt the PE 7v.. a tick slower and lot stronger than QE at 12v.

PE - 12v 2350 7v 1370 5v 979
QE - 12v 1450 7v 845 5v 604

no point working out 5 as the fan wouldn't even start, did post a graph and list with same numbers as these the curse of the "newbie".


static pressure at each speed is what matters.

 

[airdeano]

no point working out 5 as the fan wouldn't even start..

through a fan controller or PSU?
through my molex PSU connection i never had a 5v no-start. but i did through
the SATA connection. was looking to unitize connections behind mobo tray.

 

[vorticalbox]

through a fan controller or PSU?
through my molex PSU connection i never had a 5v no-start. but i did through
the SATA connection. was looking to unitize connections behind mobo tray.

the SP120 PE/QE have an operating voltage of 7 - 12 V

 

[jamesriley94]

through a fan controller or PSU?
through my molex PSU connection i never had a 5v no-start. but i did through
the SATA connection. was looking to unitize connections behind mobo tray.

Really?
I have NF-F12s that won't start through 5v on molex - and knowing you, you'll have tried them in the past.

 

[vorticalbox]

Really?
I have NF-F12s that won't start through 5v on molex - and knowing you, you'll have tried them in the past.

my fractal 140MM fan doesn't start on anything less than 12 volts, but once going i can lower the volts down to 7, this was back when i have a fan controller running.

 

[NeverBackDown]

under-volt the PE 7v.. a tick slower and lot stronger than QE at 12v.

PE - 12v 2350 7v 1370 5v 979
QE - 12v 1450 7v 845 5v 604

Does that make it quiet at 7v?

 

[airdeano]

i couldn't really tell a large diff from QE @ 12v and PE @ 7v. it might be bit louder
than QE @ 12v. i didn't use a sound level tester (should have) app.

 

[NeverBackDown]

Ok but if i have say 4 in my case(2 front 2 top) do you think they would still be loud in an R4?

 

[airdeano]

i'd doubt it. in my Midi i can barely hear the push/pull SP120PE H100 @ 7v