Easy question, running PWM fans and DC fans on Impact VII

[withalligators]

Hey guys,
Looking to put 4 fans + my Apogee Drive II pump on my Impact VII. Currently I'm running the pump and 2 cougar vortex fans. The pump is PWM sensed of the CPU fan header and powered by molex off of the PSU. The two fans are connected PWM to the Coolhub ports. I'm adding another radiator and would like to change the vortex fans to Gentle Typhoon AP-15s to keep it as quiet and cool as possible. The AP-15s are 3 pins though. Can I still run the pump via PWM off of the CPU fan header, and 2 AP-15s on Y splitters per coolhub port? They are only rated at .36A at startup surge. But will the MB be able to control their respective speeds, or do I need all PWM or all DC controlled accessories?

Cheers

[withalligators]

Really, nobody knows?

[Korth]

I don't know specifics for your Maximus Impact VII or Impact CoolHub accessory. The motherboard manual is here.

But 3-pin fans will work on 4-pin fan headers. They won't be PWM controlled but they can still operate at variable voltages/rpms. Your mobo might automatically sense/configure fan type and rpm control (I think all ROG mobos can do this, but not sure), or you might have to manually configure some per-header UEFI/BIOS option for each fan (also a common option on ROG mobos, I think). Fan autodetection typically spins up the fans at max rpms for a few seconds at startup (as defined within PWM whitepapers, whether the fans are PWM-controlled or not).

Most mobos I've seen (including all the ROG mobos I've seen) typically allow a maximum of 12V/1A (12W) per fan header. Meaning you can attach as many 12V fans in parallel as you like (through hubs/splitters/etc), so long as they don't exceed 1A/12W total.

If you haven't already got your new Typhoons then it would be better and easier (and more power efficient) to cancel the order and select comparable PWM-capable fans instead. If you're wondering whether you can use Typhoons you already have then just plug them and see if it works - again, 3-pin fans in 4-pin fan headers will work, and won't damage the motherboard or the fans, at worst they will operate at full rpms and not allow any sort of rpm control/throttling. The reverse is not entirely true, however, 4-pin PWM fans in 3-pin fan headers will also work (again, maybe only at full rpm) but the PWM components on the fans will be strained (and have a short operating life) if given variable voltage instead of pulsed 12VDC power.

I'm unsure exactly what the frequency of the pulse width on ROG PWM controllers really is, although I suspect it's likely 30Hz or 60Hz with a quick voltage skew/response time. If the frequency is too high, the PWM fan effectively "sees" power being delivered in a linear (variable voltage) fashion, which is hard on a PWM fan motor designed only for 12VDC. It the frequency is too low, the fan stutters and gets "choppy" while alternating between full/zero rpms instead of delivering a smoother rpm curve. This probably doesn't matter for your parts (all part of the consumer PC market) but it can be a compatibility consideration on some industrial/server platforms.

[sdmf74]

Im not familiar with the coolhub port either but in the bios on my M7F I can set each header to either
Pwm or DC. Your mobo should be similar. Not sure if this helps but good luck.

[withalligators]

Cool, thanks guys. Korth, if you suggest not going with the AP-15s, because they are 3pins, what fans can you recommend? I want, like everyone else, quiet and high static pressure. Everywhere I ask, people say: get APs. I was watching some computex 2015 videos (and subsequently disappointed that AMD won't release new cards until the middle of the month), when I saw that Deepcool has some interesting looking fans coming out, the TF series. Obviously there are no reviews yet, but they look promising.

[Korth]

FWIW, specs for fans - particularly their dBA output - are not really standardized or regulated. Some manufacturers are notorious assessing these metrics in "unrealistic" ways, the fans they advertise as being "quiet" are judged by many people to be not very "quiet" at all. I trust Noctua's figures because they service enterprise/server markets (and while industry isn't as demanding about low noise as home consumers would be, it is big money compared to special niche and only in Noctua's best interest to report their specs - and their specific testing methods - as accurately as possible). I am a bit apprehensive about Scythe since they hardly advertise any specs at all - the "best" information about their fans is buried within their ODM supplier's technical literature instead, and it the figures differ from what's printed on the box, and differ again from what's printed in their manuals! Not saying that Scythe fans are dishonest cheap junk (indeed, quite the opposite, they offer many excellent fan products) but I am saying that they don't seem to take their fan engineering/methodology quite as seriously as the fan-obsessed folks at Noctua.

[Korth]

Those AP-15 fans look fairly conservative (as in - not aggressively styled, lit up, and blinged out) so I'm guessing specs outweigh appearance for you. Here's a thread at OCN discussing these fans. I prefer Noctua Industrial fans, they cost more but have better specs and basically last forever. I don't think there are any 120mm fans with higher static pressure than NF-F12 industrial 2000s (3.94mm H2O), none with a spec of 29.7dBA volume (not truly as quiet as Noctua reports, but still no louder than a library and certainly quieter than 58dBA fans which sound more like little aircraft engines). BeQuiet fans don't push as much manly airflow/pressure, but there is absolutely nothing quieter.

Your non-PWM AP-15 fans are a good choice, though. Assuming your mobo and/or CoolHub can drive them - I think they can, but I don't really know. This review shows BIOS screenshots which offer a "PWM or DC" option for each fan.

If you're planning on a push-pull exhaust across your rad then you can quiet it down a lot but hurt cooling only a little when using low-pressure/high-airflow fans on the topside.

Not sure why you'd want to run the pump off the CPU header, unless it's a really loud component. I'm used to keeping pumps at full flow and controlling the fans instead (they tend to be the loudest components, especially since they're usually right up at the edges of the chassis, pushing their noise outwards). And I like having "fast" fluid flow through the blocks and rad(s), lower per-unit thermal transfer but more overall Watts moved from heating spots to cooling spots. But I suppose there's many other approaches, lol.

[withalligators]

From what I understand, and it could be wrong, Scythe didn't make the GTs, they paid Nidec Servo to slap their name on them. I believe they have since parted ways, and any GTs sold since then no longer have the Scythe name on them, and Nidec owns the rights to the motor.

And yes, I am interested performance and silence more so than in aesthetics.

That screenie of the BIOS is accurate, but that PWM/DC option only exists for the CPU Fan profile.

It's weird that for as long as the APs have been out, nothing better designed has come along and taken that crown. I'll probably get a pair and see how they sound against the rads in my tiny case.

Thanks for all your help and suggestions.