Question Case fan

[elegendx]

Hello
I want to buy fans for my computer to keep it cool and quiet.
From brands I am between Arctic, be quiet!, Corsair, Coolmaster, Noctua and Zamlan.
What role does size play in the fan and what are the differences between them?
Also fan rpm what is PRM? What should I look for in the value (number)? Should it be bigger or smaller? In addition to noise levels what is dBA? What should I look for in the value (number)? Should it be bigger or smaller? End of airflow?

 

[siaan312]

To be honest, you don't need to think about it too much.

I'm unsure of what PRM is, but dBA is decibels and lower is better.
Bigger size means more efficent fans and more torque, which is good.

Noctua is known to be the best fan manufacurer, but they are really expensive.
From my own experience, corsair and bequiet also have quality, quiet fans, but Noctua is still the best.

 

[Lafong]

What diameter fans will your case accept?

120mm? 140mm? Something else?

Generally....try to use the largest diameter that the case will accept. That is usually 120 or 140. Larger fans can move the same amount of air as smaller fans, but at a lower rpm, so less noise. Or they can move more air at the same rpm as a smaller fan.

Decide how much fan noise bothers you. Maybe not at all? Fans spinning at 2000 rpm are likely to be quite obvious at 4 or 5 feet distance.

Decide how much to worry about temperatures. Some people are extremely afraid, others not so much.

6 fans won't necessarily result in lower temperatures than 4 or 5. Some people use as many fans as their case will hold regardless, for reasons of their own.

You can probably control fan speeds in the PC BIOS.

I wouldn't buy purely on the basis of specifications shown in the specifications sheet. Differences of 3 DBA may not even be audible. Differences of more than 3 DBA might not be noticeable when the PC is 4 or 5 feet away.

Perceived noise levels are not "additive"....2 fans aren't likely to sound "twice as loud" as one fan.

Get 3 or 4 decent fans and experiment.

Standard idea is 2 in the front blowing in and 1 in the back sucking out. Try that and adjust if unhappy.

 

[geofelt]

I think PRM is a typo.
RPM or revolutions per minute is more of a metric.
What is the make/model of your case, and what are the parts inside that you need to cool?

 

[Karadjgne]

What role does size play in the fan and what are the differences between them?

Most common 2x sizes are 120mm and 140mm. The 140mm has longer blades, larger surface area, so has more potential. But everything balances. At 1000rpm each, a 140mm has more cfm (air moved) but because the tips of the blades are physically moving faster than a 120mm, it's also noisier. However, if both fans are at the same noise level, the 140mm will lower rpm and equitable cfm but the 120mm will have higher static pressure. Balance. Giveth with one hand, taketh away with the other.

In addition to noise levels what is dBA? What should I look for in the value (number)? Should it be bigger or smaller? End of airflow?

Db is decibels. That's the actual noise level. Db(A) is weighted decibels, an expression of relative 'loudness' to the human ear. For instance, a subwoofer might put out 100db at 30Hz, but that would be very low db(A) since at 30Hz you feel the pressure more than you hear it. Same 100db at 20KHz would sound like tinnitus but every dog in the neighborhood would be yelping. Same 100db at 2000Hz would be standing next to a Harley Davidson revving it's engine.

So db is one thing, but actual 'loudness' will depend on a variety of factors, such as placement in the case, orientation of the fan etc. For instance you don't really hear a psu fan at all if it's downward facing and the case fans are ramped up, even if it's technically a higher db fan.

In general, Arctic, Noctua and BeQuiet have the least loud fans and very good performance. You can get better performance from the Noctua 2000 and 3000rpm industrial series, but as with any fan, the faster it spins the 'louder' it gets, regardless of actual db.

 

[elegendx]

To be honest, you don't need to think about it too much.

I'm unsure of what PRM is, but dBA is decibels and lower is better.
Bigger size means more efficent fans and more torque, which is good.

Noctua is known to be the best fan manufacurer, but they are really expensive.
From my own experience, corsair and bequiet also have quality, quiet fans, but Noctua is still the best.

Okay. Thank you very much.

What diameter fans will your case accept?

120mm? 140mm? Something else?

Generally....try to use the largest diameter that the case will accept. That is usually 120 or 140. Larger fans can move the same amount of air as smaller fans, but at a lower rpm, so less noise. Or they can move more air at the same rpm as a smaller fan.

Decide how much fan noise bothers you. Maybe not at all? Fans spinning at 2000 rpm are likely to be quite obvious at 4 or 5 feet distance.

Decide how much to worry about temperatures. Some people are extremely afraid, others not so much.

6 fans won't necessarily result in lower temperatures than 4 or 5. Some people use as many fans as their case will hold regardless, for reasons of their own.

You can probably control fan speeds in the PC BIOS.

I wouldn't buy purely on the basis of specifications shown in the specifications sheet. Differences of 3 DBA may not even be audible. Differences of more than 3 DBA might not be noticeable when the PC is 4 or 5 feet away.

Perceived noise levels are not "additive"....2 fans aren't likely to sound "twice as loud" as one fan.

Get 3 or 4 decent fans and experiment.

Standard idea is 2 in the front blowing in and 1 in the back sucking out. Try that and adjust if unhappy.

Okay I understood. I will want to change sometime fans my pc case. Thank you very much.

I think PRM is a typo.
RPM or revolutions per minute is more of a metric.
What is the make/model of your case, and what are the parts inside that you need to cool?

Thank you for correcting me. My pc case is Silent Base 802 by be quiet. Also, the parts my pc are

• Motherboard: ASUS ROG STRIX B550-F GAMING (WI-FI)
• Graphics Card: ASUS ROG -STRIX-RTX3060TI-O8G-V2-GAMING NVIDIA GeForce RTX 3060 Ti 8 GB GDDR6
• CPU: AMD Ryzen 9 5900X Box
• SSD OS: Samsung 980 Pro SSD 1.0TB M.2 NVMe
• SSD Data: Samsung 870 QVO SSD 2TB 2.5
• RAM: G.Skill TridentZ Neo 32GB DDR4-3200MHz (F4-3200C16Q-32GTZN)
• HDD Data: Seagate Barracuda 4TB
• HDD Data: WD Red Plus 4TB
• PSU: Corsair Power Supply 850W ATX 24 pin RM850x (2021)
• CPU Cooler: Noctua NH-D15 chromax.black

Most common 2x sizes are 120mm and 140mm. The 140mm has longer blades, larger surface area, so has more potential. But everything balances. At 1000rpm each, a 140mm has more cfm (air moved) but because the tips of the blades are physically moving faster than a 120mm, it's also noisier. However, if both fans are at the same noise level, the 140mm will lower rpm and equitable cfm but the 120mm will have higher static pressure. Balance. Giveth with one hand, taketh away with the other.

Db is decibels. That's the actual noise level. Db(A) is weighted decibels, an expression of relative 'loudness' to the human ear. For instance, a subwoofer might put out 100db at 30Hz, but that would be very low db(A) since at 30Hz you feel the pressure more than you hear it. Same 100db at 20KHz would sound like tinnitus but every dog in the neighborhood would be yelping. Same 100db at 2000Hz would be standing next to a Harley Davidson revving it's engine.

So db is one thing, but actual 'loudness' will depend on a variety of factors, such as placement in the case, orientation of the fan etc. For instance you don't really hear a psu fan at all if it's downward facing and the case fans are ramped up, even if it's technically a higher db fan.

In general, Arctic, Noctua and BeQuiet have the least loud fans and very good performance. You can get better performance from the Noctua 2000 and 3000rpm industrial series, but as with any fan, the faster it spins the 'louder' it gets, regardless of actual db.

Okay. Thank you very much.

 

[Paperdoc]

Both fan speed (RPM) and size certainly impact cooling capacity. But it's better to narrow down to other specs because all cooling is done by air FLOW. So look at the spec of Air Flow. It is really the MAX the fan can do when operating at its max speed, and with no resistance to air flow (backpressure). Watch for units of air flow measurement. Most are shown in CFM - Cubic Feet per Minute. But some are in m³/hr - Cubic Metres per Hour - conversion factor is 1 m³/hr = 0.59 CFM. In actual use the real air flow you get depends on how the cooling control system has set the fan speed, and is also reduced somewhat by things on the flow path that interfere with air flow.

Fan speed impacts fan noise (measured in dBA), but also is heavily affected by fan design. So the dBA spec is the MAX noise you get at max fan speed, and this will be different for different fans. Actual noise will be less when the fan is not full speed.

Fans are designed usually optimized for two classes of application. The spec to look for is Backpressure (or just Pressure) expressed as mm of water. "Air Flow" fans are designed for uses with little interference with air flow such as cases, and typically have ratings of less than 0.75 mm. "Pressure" fans are for places with restricted air flow paths like the fins of a heat exchanger on a CPU cooler, or a finned radiator. For those applications you need Pressure rating of 1.5mm or more - over 2 mm is better. Usually for very similar fans the "Pressure" design will have slightly lower max air flow, but it CAN push that air through more resistance. Any fan's actual flow generated is reduced by air flow resistance, and the "Pressure" spec is the max backpressure that will still allow a little bit of air flow.

In a computer system operating with automatic control of the cooling fans according the temperatures measured by sensors (the default means of control), the system will adjust fan speeds to what is needed, and that will be LESS than max speed. When you compare the specs for two different fans, bear in mind that the fan with the higher MAX Air Flow spec normally will actually operate at a LOWER speed than the other fan, and that means two things. One is that its noise will be reduced, MAYBE less than the noise of the other fan for the same cooling effect. The other is that this fan has MORE "reserve capacity" to speed up and create more cooling when your system is working harder and producing more waste heat.