What PC fans do you use and prefer?

[watzup_ken]

Starting a discussion to see what fans do you folks use/ prefer?

Just sharing my experience with the fans I've experienced and my preference. For me, I always prioritise airflow in the case, so I tend to play around with different fans to get a good balance between airflow and noise. I am not going into details, but just sharing my experience so that you can then go and check out for reviews of the fan and decide if it suits you. As you can tell, there is not RGB fans because I prefer a black out system.

1. SanAce 120mm - This is one of my early favourite fan that I used in my early DIY days. I believe I got these and also a pair of Delta fans from Gary, the shop at level 2 over SLS, many years back. I still have 2 of these made in Japan fans. I feel the air pressure is quite good and the fan ran quite quiet. These are non PWM fans by the way and are I think at least a decade old. Still working well fortunately.

2. Corsair ML120/140 - Had a couple of the ML120 and 1x 140mm, and to be honest, these are fans I dislike most. Airflow is great, but it sounds like a cordless vacuum at full throttle.

3. Fractal Design Venturi 120mm - I feel this is a fan that is a good balance between airflow/ pressure and noise. I used this on my HTPC cooler, ID Cooling IS 50, and it worked very well and silently.

4. Arctic P12 - These are one of the best value fans I've ever used. I think there are a lot of reviews on them, so the reviews speak for themselves. In particular, I feel that the BionIX P12 are generally overlooked. These spins faster and are also very silent even at full speed. If you are looking for cheap and good fans, I strongly recommend this.

5. XPG Vento Pro (aka Gentle Typhoon) - I've never tried a Gentle Typhoon in the past, but recently got a few of these to try out. Airflow wise, its excellent, beating even the P12 BionIX based on my subjective experience. Noise level is however, quite a fair bit higher when comparing at full speed. I got this over the Noctua NF A12 because they are cheaper.

6. Phantek T30 - Just ordered this to try out. Will update.

In terms of top 2 preference for 2021,
1. Arctic BionIX P12 - It is cheap and works really well. The downside is that the build of the fan is not as sturdy as say a Vento Pro.

2. Vento Pro - Based on reviews out there, the Gentle Typhoon here have a slight edge in terms of airflow due to higher RPM. But the noise level is higher. The reason for recommending these is because they are cheaper. These may however get replaced by the T30 that I just ordered.

 

[Yongkit]

I am currently using 1 XPG Vento Pro.

Air flow is very good and yes you are right its noise level also higher.

I used it as middle front case fan (at 100% capacity) to blow directly to my GPU for better heat dissipation as my case is consider huge (Phantek Evolv ATX) having a long distance from case fan to 3080 GPU with approx. 11cm gap.

 

[86technie]

- Cooler Master Sickleflow 120mm (Not to be confused with earlier version.)
- CM 140mm case fan (Rare, only use for top exhaust with CM 69X series casing.)
- CM 200mm case (Rare, retro fan, case specific usage only.)

For me I have use up to 200mm, bigger the fan more airflow but more dust.
The new Sickleflow compare with older one I also use, the newer model is quieter than older during high RPM.
All the fan I used are normal LED light no RGB or ARGB, I not only don't like fancy lights but also the cable mess it will create.

Generally if you ask me is 120mm good enough? I would say yes, 140mm and above depend on case as not all case especially budget one supports such big size fan.

 

[Psycovirus]

Amazing Fans

Noctua NF-A12x25

Replaced 3x Generic noisy 120mm Fans with 3x Noctua NF-A12x25 in my 3U 16 Bay NAS chassis.

Lots of Air Flow through restricted front intake with HDDs and cables and backplane in the way. Whisper quiet too. Now I can only hear the back 2x 60mm exhaust fans. Maybe I should replace those with Noctua fans too.

Pretty OK Fans:

BeQuiet! Silent Wings 3, 140mm Fans: Not a bad fan, whisper-quiet up to 1200 RPM. Audible if it goes above that. Not the quietest or best fan at 120mm/140mm. I got mine at 50% off each so it was pretty good.

Fractal Design Dynamic X2 GP-14, Free case fans for their cases. Only goes up to 1000 RPM, no PWM. Functional and good airflow. Not audible at all at max speed. Prefer Silent Wings 3s.

Noisy Bad Fans:

NZXT AER 140mm fans that came with x62 AIO. Bad fans, noisy above 900 rpm, it has a weird hum around 1.1k RPM. Hate them. Replaced them with 140mm Silent Wings 3

I wish to try the new Fractal Design's 180mm Fans and their Torrent case.

 

[elmariachi]

Wah got people also use the XPG Vento Pro fans here. I love mine and the fact you can daisy chain them. Beautiful thing about this is that you can use 6 fans on 1 header and still be just under 1A. Cleans up quite alot of clutter. Static pressure rating is also better than many out there and at full speed, they sounded much quieter than my previous X3M Vardar fans from EK.

But the new kid on the block is the Phanteks T30 fans but they cost alot and sounds quiter than the competition. But these fans are 30mm profile thick not the usual 25mm. The bad thing is that there is a switch to toggle 3 fan modes and it's impractically placed. You have to remove the fans to toggle this switch. That aside, these are the best fans out there today. Period.

But honestly if you're already on good fans like the XPG, the performance difference is going to be minimal unless you want a quieter system. And of course if you want the 3000rpm mode. But 3000rpm mode is not worth unless you're gonna bench but not a daily mode and the fact you have to remove these fans to change the mode makes it pretty damn inconvenient.

 

[Lastwishes]

Had 6 of the original gentle typhoons. Great fans, but 4 of them eventually developed a ticking sound after year 8 or so. I thought about getting the XPG Vento Pros to replace them, but I'm holding out for Noctua A12x25s in chromax, which keeps getting delayed.

Currently using a mix of Arctic P12s, P14s and Noctua A15s. The arctic fans are value kings.

A15s despite being Noctua, are only okay - they're actually quite audible at <90% rpm. Noctua A9x25s (I use these on my gpu) are much quieter even at 100% rpm.

Also tried out Silverstone Air Penetrator 141; I think the wind tunnel thing is for niche use/gimmicky but it performs decent. Rather noisy though at full speed though. Price wise they're terrible - I'd rather go noctua or XPG Ventos.

I use Fractal design GP-14s on a spare rig - decent, but not amazing performance wise.

Still have some Noiseblockers (lasted longer than my Gentle Typhoons, despite being a rifle bearing fan), and Zalman F3s (actually pretty good for their age).

Edit: Thanks for sharing on the T30s. Wasn't aware of this fan, but I think this was exactly what I was looking for (just ordered a 3 pack).

 

[watzup_ken]

Wah got people also use the XPG Vento Pro fans here. I love mine and the fact you can daisy chain them. Beautiful thing about this is that you can use 6 fans on 1 header and still be just under 1A. Cleans up quite alot of clutter. Static pressure rating is also better than many out there and at full speed, they sounded much quieter than my previous X3M Vardar fans from EK.

But the new kid on the block is the Phanteks T30 fans but they cost alot and sounds quiter than the competition. But these fans are 30mm profile thick not the usual 25mm. The bad thing is that there is a switch to toggle 3 fan modes and it's impractically placed. You have to remove the fans to toggle this switch. That aside, these are the best fans out there today. Period.

But honestly if you're already on good fans like the XPG, the performance difference is going to be minimal unless you want a quieter system. And of course if you want the 3000rpm mode. But 3000rpm mode is not worth unless you're gonna bench but not a daily mode and the fact you have to remove these fans to change the mode makes it pretty damn inconvenient.

I was thinking the T30 may cost more, but they are selling at Amazon at around 125 bucks for a bundle of 3. So still cheaper than the Noctua NF A12. At least from all the reviews I've watched, the T30 have an advantage in airflow at low RPM. Other benefit is that it can go up to 3000 RPM if required, but would sound terribly loud.

I wanted to try the T30 mainly because of the added thickness. Currently, I am using the XPG Vento at the base of the NR200 ITX case, which also doubles up as the GPU fan because I've deshroud it. The added thickness of the T30 may bring the fan closer to the heatsink, which I feel may be beneficial.

 

[elmariachi]

I was thinking the T30 may cost more, but they are selling at Amazon at around 125 bucks for a bundle of 3. So still cheaper than the Noctua NF A12. At least from all the reviews I've watched, the T30 have an advantage in airflow at low RPM. Other benefit is that it can go up to 3000 RPM if required, but would sound terribly loud.

If you can go 30mm thickness then it's a possible consideration. But 3000rpm is definitely not a daily setting and sure as hell not a flick of switch with it installed. So if your specific requirement of decent airflow at low rpm, then also make sure your radiator setup matches as some radiators depending on thickness needs >1,200rpm for optimal performance. Slim radiators do not function well with low rpm setups, mid sized radiators good with low rpm setups and thick radiators require >1,700rpm for optimal performance. So you have to decide your radiator setup before you decide your fans. If you're just using it for case fans, it's a waste really. These are designed for static pressure applications.

 

[watzup_ken]

If you can go 30mm thickness then it's a possible consideration. But 3000rpm is definitely not a daily setting and sure as hell not a flick of switch with it installed. So if your specific requirement of decent airflow at low rpm, then also make sure your radiator setup matches as some radiators depending on thickness needs >1,200rpm for optimal performance. Slim radiators do not function well with low rpm setups, mid sized radiators good with low rpm setups and thick radiators require >1,700rpm for optimal performance. So you have to decide your radiator setup before you decide your fans. If you're just using it for case fans, it's a waste really. These are designed for static pressure applications.

I feel the static pressure should help with pushing air through the GPU heatsink as the fans are doing double duty as case and GPU fans. Right now, after installing the Vento Pro, the gap between the fan and the GPU heatsink is still quite big. Need to measure the length of the gap, but my hand should be able to fit in the gap quite easily.

 

[Lastwishes]

I was thinking the T30 may cost more, but they are selling at Amazon at around 125 bucks for a bundle of 3. So still cheaper than the Noctua NF A12. At least from all the reviews I've watched, the T30 have an advantage in airflow at low RPM. Other benefit is that it can go up to 3000 RPM if required, but would sound terribly loud.

I wanted to try the T30 mainly because of the added thickness. Currently, I am using the XPG Vento at the base of the NR200 ITX case, which also doubles up as the GPU fan because I've deshroud it. The added thickness of the T30 may bring the fan closer to the heatsink, which I feel may be beneficial.

I'm curious, how are your GPU temps with the Vento + deshroud?

I've seriously considered shifting my set up to an ITX in the NR200P just for the deshrouded GPU + good 120mm fan set up. I didn't do it in the end as I realised it just didn't fit my use case - I don't really have a problem with big cases, and preferred towers anyway. In the end I deshrouded my gpu and jerry-rigged Noctua A9s to the heatsink instead, and the improvement was very significant. I've read on reddit that 120mms aren't really ideal for the gpu given the big deadzone in the fan hub, and there's also a loss of pressure from the overhang of the 120mm fan size.

If you can go 30mm thickness then it's a possible consideration. But 3000rpm is definitely not a daily setting and sure as hell not a flick of switch with it installed. So if your specific requirement of decent airflow at low rpm, then also make sure your radiator setup matches as some radiators depending on thickness needs >1,200rpm for optimal performance. Slim radiators do not function well with low rpm setups, mid sized radiators good with low rpm setups and thick radiators require >1,700rpm for optimal performance. So you have to decide your radiator setup before you decide your fans. If you're just using it for case fans, it's a waste really. These are designed for static pressure applications.

I'm planning to using the T30s as intake case fans behind a mesh. While I agree that it's not an optimal use of the fan, it's not exactly a waste. Good fans last a long time, and a cool but silent pc is worth it to me at least. I think the sticking point is just the price, but I think since I was already planning to pay more for noctua a12s, the T30s would be a no brainer.

 

[royfrosty]

I have been going through a couple of radiator fans since my early days of custom water cooling. I believe it was 7 years ago, my first radiator fans that i used was....

Enermax UCCLA12P (i believe this is the model) - this fan is so cool, the fan blades are detachable. Yes, you didnt hear me wrong. And during that time, white led and white fans are not common. Cleaning and mantaining it is simple. I can just remove the blades and litterally wash it. Frame dirty? Just use a damp cloth. However, this fan doesnt move much air. Quite crappy to be a radiator fan. But back then i was using dual 480mm monsta rads from alphacool. I can even afford to run these fans at an insane 400rpm to cool everything.

After which i moved on to Gentle Typhoon AP-1800 (which is renamed now to XPG Vento), yes this was the king of radiator fans in those days. Nidec fans are famous for their airflow, yet produce a unique signature sound that oddly did not sound bad or annoying. Is forgivable. Hence i do run it at a diserable higher rpms for more cooling performance as it wasnt noisy imho. I even pull off a single Hardwarelab Genesis GTS 360mm slim rad to cool both my overclocked i7-5820k and gtx1080 back then with the Original Lian Li O11 casing (not to be confused with the current gen O11 series) I even painted it white as white fans were still not popular back then.

After which i moved on to EK Vardar F4 120ER version. This was a complete different. It was able to operate at 0rpm with modern motherboards. I was running it with Hardwarelab Genesis GTS 360mm slim rads again (seriously, this slim rads are awesome). The ability to turn off during certain temperature was indeed the best one i had used. Combine with temperature probe, i was able to only kickstart the fans when i hit a certain coolant temperature.

The next fan i gotten was from Gentle Typhoon again. This time round model AP-29. This was the fan that was strapped on to the r9 Fury X. It was Cooler Master AIO with Gentle Typhoon AP-29. It was also in black and damn this unit moves way more air than any 120mm fans. Even till today. Its one of the best 120mm fans i ever used. The down side, it cannot run at below 800rpm iirc and it gets darn loud at 3000rpm lol.

After which i told myself, i dont need super high performance. I wanted some rgb. Damn i regret it. Lian Li SL120. This is by far the worse fans of the bunch. Weak and doesnt move much air. Temperatures were also a little high across.

Now im in search for another fan for my new upcoming rig. Hope there is something caught my eye.

 

[KleoZy]

Nice write out. watup_ken and royfrosty.

my pick on 120mm fans are as follow
1st choice Arctic P12 PWM PST Co (drawing current 0.08)
Though they can compete with a Nidec, but airflow is not as strong as Gentle Typhoon. good and cheap but it does whine at a specific rmp between 1450 to 1550. very annoying whinning.

2nd choice Nidec Gentle Typhoon @1800 RPM (3pin which runs at full speed, drawing current 0.083a)
I can hear noise but is gentle with 9 fans installed, no harsh hissing or whining.

3rd Ek Vardar Evo ER120 (drawing current 0.18a)
Yes rgb, they are noisy at full rpm but if you tune it properly to run at max 1800rpm. it's rock solid plus the rgb are vibrant.

the three fans above as mention, they can use both on case and on rads. no issue. best part is, these three are amoung the lowers ampere usage compared to others.

as for argb fans. I agreed with royfrosty. infact argb fans generate more heat to the case, 1st their argb led. it may look cool and can switch off but having it on all the way.. not my cup of tea. the SL120 and AL120 to be honest is more toward vanity than to a actual performing fan.

Spoiler: Just My Opinon about Noctua NF A12 x 25

hmm noctua, not sure is it me or just jinx. first test conducted I borrowing the NF A12x25 from a friend, I question myself , why was it so weak? I thought the fan is faulty or something. So giving it a benefit of doubt, I did up another test and this time I bought one (totally regret). Seriously what so great about Noctua? it can't even lay a finger on cheap Arctic P12 nor the Gentle Typhoon. Plus it's running at 0.14a as compared to Arctic or Gentle which are at 0.08a and 0.083a, almost half the strenght needed, yet the airflow over powered the noctua.

Testing without an anomometer and this fan was borrowed from a friend.



Testing with an anomometer (I purchase this fan new and regreted it)

 

[Entry Level PC]

0x Fan
Open Air Casing

Cleaning = 5 mins per Quarter Year with my leaf blower

 

[NightRaven49]

was using tecware 120mm fans included with the nexus m. usually ran them at full speed and was quite noisy even after placing case on the floor. quite poor quality also, after a year of use would begin to rattle and require oiling of the bearings.

after switching my case, i got 2 arctic p12 pwm pst fans to go along with it. because it was the pst variant, i was able to daisy chain both of them as intake and use only 1 fan header on my gpu, while using the remaining header for my exhaust fan. as they were directly pushing air into the gpu, i could run very low rpm (750rpm) while idle to improve temps (>7 deg reduction) for basically noiseless operation. even setting them to run at 1500rpm maximum under load my new build is noticeably quieter than my old rig, while also allowing my gpu to run at not just out of the box clocks (would throttle in the nexus m) but also at healthy overclocks at an acceptable noise level. very satisfied especially considering i spent under $25 for both, which wouldnt even net me 1 nf a12.

 

[watzup_ken]

I'm curious, how are your GPU temps with the Vento + deshroud?

I've seriously considered shifting my set up to an ITX in the NR200P just for the deshrouded GPU + good 120mm fan set up. I didn't do it in the end as I realised it just didn't fit my use case - I don't really have a problem with big cases, and preferred towers anyway. In the end I deshrouded my gpu and jerry-rigged Noctua A9s to the heatsink instead, and the improvement was very significant. I've read on reddit that 120mms aren't really ideal for the gpu given the big deadzone in the fan hub, and there's also a loss of pressure from the overhang of the 120mm fan size.


I'm planning to using the T30s as intake case fans behind a mesh. While I agree that it's not an optimal use of the fan, it's not exactly a waste. Good fans last a long time, and a cool but silent pc is worth it to me at least. I think the sticking point is just the price, but I think since I was already planning to pay more for noctua a12s, the T30s would be a no brainer.

Unfortunately bro, I don't have a like for like temperature comparison at this point in time. I made the deshroud and changed fan hastily, so the only game I was playing was Control using Game Pass which expired a day before the mod. In my opinion, the result isn't as good as I expected. When running say Metro Exodus EE, the peak temp I saw was around 75 degrees on my RTX 3080 undervolt to 900mV, as compared to the stock fan with 2 slim fan at the bottom, I observed temps capping out at 69 degrees in Control. I suspect the big gap between the bottom fans and the heatsink is quite big, so the air may not be pushed through the fins fast enough. In addition, the Vento Pro seems to be quite loud at high RPM, so I had to limit the speed to around 60%, and I can still hear a whine. I am using a Noctua NA-FC1 to fix the speed to around 60%. The funny thing is, when I tested the fan outside the case, it sounded ok. Somehow the noise seems amplified in the casing. Haha.

 

[watzup_ken]

I have been going through a couple of radiator fans since my early days of custom water cooling. I believe it was 7 years ago, my first radiator fans that i used was....

Enermax UCCLA12P (i believe this is the model) - this fan is so cool, the fan blades are detachable. Yes, you didnt hear me wrong. And during that time, white led and white fans are not common. Cleaning and mantaining it is simple. I can just remove the blades and litterally wash it. Frame dirty? Just use a damp cloth. However, this fan doesnt move much air. Quite crappy to be a radiator fan. But back then i was using dual 480mm monsta rads from alphacool. I can even afford to run these fans at an insane 400rpm to cool everything.

After which i moved on to Gentle Typhoon AP-1800 (which is renamed now to XPG Vento), yes this was the king of radiator fans in those days. Nidec fans are famous for their airflow, yet produce a unique signature sound that oddly did not sound bad or annoying. Is forgivable. Hence i do run it at a diserable higher rpms for more cooling performance as it wasnt noisy imho. I even pull off a single Hardwarelab Genesis GTS 360mm slim rad to cool both my overclocked i7-5820k and gtx1080 back then with the Original Lian Li O11 casing (not to be confused with the current gen O11 series) I even painted it white as white fans were still not popular back then.

After which i moved on to EK Vardar F4 120ER version. This was a complete different. It was able to operate at 0rpm with modern motherboards. I was running it with Hardwarelab Genesis GTS 360mm slim rads again (seriously, this slim rads are awesome). The ability to turn off during certain temperature was indeed the best one i had used. Combine with temperature probe, i was able to only kickstart the fans when i hit a certain coolant temperature.

The next fan i gotten was from Gentle Typhoon again. This time round model AP-29. This was the fan that was strapped on to the r9 Fury X. It was Cooler Master AIO with Gentle Typhoon AP-29. It was also in black and damn this unit moves way more air than any 120mm fans. Even till today. Its one of the best 120mm fans i ever used. The down side, it cannot run at below 800rpm iirc and it gets darn loud at 3000rpm lol.

After which i told myself, i dont need super high performance. I wanted some rgb. Damn i regret it. Lian Li SL120. This is by far the worse fans of the bunch. Weak and doesnt move much air. Temperatures were also a little high across.

Now im in search for another fan for my new upcoming rig. Hope there is something caught my eye.

May be you can consider trying the Arctic P12 RGB fans. I tend to avoid anything RGB, but I think at least the P12 is a tried and tested fan, plus, if you get from Amazon, they tend to be quite affordable.

 

[royfrosty]

Actually after trying so many case with fan/rad combo. The best i gotten was just the original lian li o11 with just single 360mm rad.

There is this something about lian li cases that has a well thought out design balancing between airflow and aesthetics.

Even their current o11 series improves even more by allowing more radiators to be mounted.

Till then i realised that the need for super towers are really too niche. It was so niche that i threw my Corsair 900D away. Nobody wants it. Be it carousell, be it giving the rag and bone man as it was too heavy for him, and even giving it to people and people just turn it down lol.

Also i learn more about the ability of radiators cooling capacity. Things like surface area > thickness. And also things like hardware labs are like the godlike tier of radiators pulling off way better cooling than some thick ar$e competing radiator brands.

Finally fans are also very important. In fact im glad this thread existed/created. Fans are really a hit or miss. Not all fans works till some one actually tried it and feedback. Ang mo reviews can paint a 1000 pictures about how good a certain brand of fans. They do have forgivable weather at times. To some of them, as long as it doesnt go too high temps, it is fine.

But when it comes to our climate, every degC difference indeed make a difference. Is our sunny and humid climate that makes us consider to buy good fans.

 

[Lastwishes]

Unfortunately bro, I don't have a like for like temperature comparison at this point in time. I made the deshroud and changed fan hastily, so the only game I was playing was Control using Game Pass which expired a day before the mod. In my opinion, the result isn't as good as I expected. When running say Metro Exodus EE, the peak temp I saw was around 75 degrees on my RTX 3080 undervolt to 900mV, as compared to the stock fan with 2 slim fan at the bottom, I observed temps capping out at 69 degrees in Control. I suspect the big gap between the bottom fans and the heatsink is quite big, so the air may not be pushed through the fins fast enough. In addition, the Vento Pro seems to be quite loud at high RPM, so I had to limit the speed to around 60%, and I can still hear a whine. I am using a Noctua NA-FC1 to fix the speed to around 60%. The funny thing is, when I tested the fan outside the case, it sounded ok. Somehow the noise seems amplified in the casing. Haha.

Thanks for sharing. I think that's actually not too bad. Out of curiosity I went to try out 3dmark with clocks set to 1975/900, and peaked at about 72 degrees on my regular fan curve. But I did reapply paste as well as changed pads, which helps.

The old GTs has a hum at certain RPMs iirc, maybe that could explain the whine. Definitely the gap does have an impact, which is why some modders who use 120mm fans 3d printed a shroud to redirect the airflow into the heatsink.

Thanks for starting this thread. I've been waiting for the noctua chromax a12s forever, now I'm looking forward to the T30s

 

[SEvsNK]

Just ordered some T30s as well. Hope they impress

 

[KleoZy]

Actually after trying so many case with fan/rad combo. The best i gotten was just the original lian li o11 with just single 360mm rad.

There is this something about lian li cases that has a well thought out design balancing between airflow and aesthetics.

Even their current o11 series improves even more by allowing more radiators to be mounted.

Till then i realised that the need for super towers are really too niche. It was so niche that i threw my Corsair 900D away. Nobody wants it. Be it carousell, be it giving the rag and bone man as it was too heavy for him, and even giving it to people and people just turn it down lol.

Also i learn more about the ability of radiators cooling capacity. Things like surface area > thickness. And also things like hardware labs are like the godlike tier of radiators pulling off way better cooling than some thick ar$e competing radiator brands.

Finally fans are also very important. In fact im glad this thread existed/created. Fans are really a hit or miss. Not all fans works till some one actually tried it and feedback. Ang mo reviews can paint a 1000 pictures about how good a certain brand of fans. They do have forgivable weather at times. To some of them, as long as it doesnt go too high temps, it is fine.

But when it comes to our climate, every degC difference indeed make a difference. Is our sunny and humid climate that makes us consider to buy good fans.

Yup Ang Mo like to just show you product, do the noise test and throw you the graph and start talk about temperature. it is lenghty to produce actual test to show viewers on how the fan actually cool your system.
I am very sceptic to all fan reviews as most give graphs, yes it does give you the gauge but how good are they to be used in conditional like in Singapore.

anyway about the O11D from lian li. if you have not notice.. fan noise are often from the bottom, where it sucks air in and there are lose holes which causes whistling hiss sound. I have done a couple of builds for friends with the O11D series, including my O11D mini. Once block those empty slots, mircally the aweful whistling hiss sound goes off.