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Cooling in the new 2020 27" iMac?

What I don't understand is why a fan in 2017 i5 at 1200 rpm is quieter than a fan in 2020 i7 at 1200 rpm. This has nothing to do with heat. 1200 rpm is 1200 rpm.

One theory is that the fans are different and the latter can push more air out. The difference in volume of air moving in the internal ducts and out of the thin vents generates more noise.

BTW My new iMac just had a kernel panic while I was typing this and restated itself.
 
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edib said:
What I don't understand is why a fan in 2017 i5 at 1200 rpm is quieter than a fan in 2020 i7 at 1200 rpm. This has nothing to do with heat. 1200 rpm is 1200 rpm.

One theory is that the fans are different and the latter can push more air out. The difference in volume of air moving in the internal ducts and out of the thin vents generates more noise.

BTW My new iMac just had a kernel panic while I was typing this and restated itself.
Click to expand...

Is this your first kernel panic on the new iMac? Been hearing some people complain about this as well on the forum
 
mindquest said:
Is this your first kernel panic on the new iMac? Been hearing some people complain about this as well on the forum
Click to expand...

Yes, it is the first one. Brand new machine, arrived yesterday. I only had Safari running at the time.
 
edib said:
What I don't understand is why a fan in 2017 i5 at 1200 rpm is quieter than a fan in 2020 i7 at 1200 rpm. This has nothing to do with heat. 1200 rpm is 1200 rpm.

One theory is that the fans are different and the latter can push more air out. The difference in volume of air moving in the internal ducts and out of the thin vents generates more noise.

BTW My new iMac just had a kernel panic while I was typing this and restated itself.
Click to expand...

Has anyone figured out if they’ve changed the hardware parts of the fan over 2017-2020? I ask I’ve I’ve been watching this thread and testing my 2017 i7 out for noise. At idle the fan does run at 1200rpm but is practically silent in my work room i.e. when sitting in front of the screen, I cannot hear it.
 
wardie said:
Has anyone figured out if they’ve changed the hardware parts of the fan over 2017-2020? I ask I’ve I’ve been watching this thread and testing my 2017 i7 out for noise. At idle the fan does run at 1200rpm but is practically silent in my work room i.e. when sitting in front of the screen, I cannot hear it.
Click to expand...
I think the OWC teardown mentioned it’s the same fan components used as 2019. Don’t know if 2019=2017.
 
CheesePuff said:
I'm still surprised to read some of these replies, I have now been using my iMac 2020 (i7, 32 GB RAM, 512 GB SSD) for almost a week now, and in my silent office as I type this and put my ear right up to the screen, I can hear zero noise at all, not even the fan spinning at its idle speed.
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interesting. it sounds like quality comtrol or perhaps iMacs are being made at more thn one production line with different internal parts? i sent back 2 2019 loaded iMacs due to whining fan noise at idle
 
tbcuthbert said:
interesting. it sounds like quality comtrol or perhaps iMacs are being made at more thn one production line with different internal parts? i sent back 2 2019 loaded iMacs due to whining fan noise at idle
Click to expand...
It would be interesting to compare the same configurations assembled at different factories from China and Ireland.
 
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I still believe it's down to one's personal hearing/sensitivity and environment. Really, I have had 5 iMacs and I was able to hear the fan spinning at 1200 rpm or 1100 rpm (iMac Pro respectively) with all of them. One of them was clearly defective (fan made a terrible whining noise) but the rest of them lead me to the conclusion that there is no silent iMac out there. If you get along with it, great. I also do not believe any part is made in Ireland. It's all from China.
 
wardie said:
Has anyone figured out if they’ve changed the hardware parts of the fan over 2017-2020? I ask I’ve I’ve been watching this thread and testing my 2017 i7 out for noise. At idle the fan does run at 1200rpm but is practically silent in my work room i.e. when sitting in front of the screen, I cannot hear it.
Click to expand...
CheesePuff said:
EveryMac does show only the 5700 XT as using the 20,2 identifier: https://everymac.com/ultimate-mac-lookup/?search_keywords=iMac20,2
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Some have postulated that iMacs identified as 20,2 all have the 5700XT GPU (or possibly the 5700 GPU). Is it also possible that the 20,2 iMacs have a different (noisier and higher flow) fan than the 20,1 iMacs? To account for the greater heat from the 5700(XT)?
It is confusing there seems to be little consensus whether the 2020 fan is noisier than previous iMacs. Does anyone who has a 5500XT or 5300 GPU have a fan noise problem?
 
wilberforce said:
Some have postulated that iMacs identified as 20,2 all have the 5700XT GPU (or possibly the 5700 GPU). Is it also possible that the 20,2 iMacs have a different (noisier and higher flow) fan than the 20,1 iMacs? To account for the greater heat from the 5700(XT)?
It is confusing there seems to be little consensus whether the 2020 fan is noisier than previous iMacs. Does anyone who has a 5500XT or 5300 GPU have a fan noise problem?
Click to expand...

I have the 5300. No fan noise problem; just a heat problem with the CPU.
 
I have an i9, 5700 XT, VESA mount. Personally I would describe it as a very silent computer. (I do video editing in FCPX with 4K 10 bit MXF files from a canon C300 mkII) and im connected to a 4K OLED LG C9 for a secondary monitor. It isn't silent, if I listen I can hear it, but is it annoying? Not to my ears.

In our house we have a low noise central heating pump, wich I can hear, does it annoy no. We have a low noise ventilating system - again if I listen I can hear it, but it isn't annoying. My MacBook Pro 16 (i9, 5500m 8GB) on the other hand is noisy to the point, where I just want to throw it out the window, same thing could be said (when under load) with the 2017 iMac (maxed out) I used previously.

The above do apply to my unit, I do believe that there are some difference to specific units, just as it is the case with coil whine, screen uniformity etc.
 
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wilberforce said:
Some have postulated that iMacs identified as 20,2 all have the 5700XT GPU (or possibly the 5700 GPU)
Click to expand...

My 5700 model is iMac 20,2

Fan spins at 1200. Whether I can hear it or not depends on the noise floor. With no wind outside, windows closed I can just hear it. With wind blowing outside or windows open in my office I can't hear it. It is quieter than my 2017 iMac - which has a hum from the hard drive.
 
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I just received my 2020 iMac replacement for my 2014 iMac (first 5K 27" model), and can make side-by-side comparisons.
Mine is an i7 with 5500 XT.
The fan on the 2020 iMac is noticeably louder and more air flow than on the 2014, when both are running at 1200 rpm (according to MacsFanControl).
On my 2014 the fan at 1200 rpm is barely audible, and I have to put my ear close to the vent at the back to hear it, and can barely feel any airflow on my hand. (It has always been like this, from day one in 2014).
On the 2020 I can just hear it from the front of the machine (in a quiet room), and can easily feel much more airflow, at the same reported 1200 rpm.
If the reported rpm is correct (1200), it seems the fan design has been somehow changed to produce more airflow, perhaps with different fan blade shape or size - I don't know.
It is still a very quiet fan, and does not bother me, but it is a noticeable change.
Something to consider for those that are very sensitive to fan noise.
IMO the fan noise when running at minimum rpm is the most important consideration for noise: this is the condition for 99% of the time.
Everything else about the 2020 iMac is a welcome improvement over the 2014 - speed, screen, etc
 
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mj_ said:
You can lower idle RPM to ~950rpm on an iMac with a trick:


View attachment 941931
View attachment 941933
Install smcFanControl, then open Terminal and copy and paste the following:



Afterwards, launch (or relaunch) MacsFanControl (it's important to launch or relaunch it after you've modified SMC, otherwise it won't be able to detect the new minimum), set your fan control to manual and adjust the values for start and maximum temperature to your liking. There's a noticeable difference between 1,200 and 950rpm, and it made a huge difference for me.
Click to expand...

Is anyone able to apply this to a 2020 iMac? Gets me an error message.
 
Just setup my new 2020 iMac, it is the i5 base model. I can confirm a coarse and quite noticeable fan noise at idle.
 
diabora said:
I have an i9, 5700 XT, VESA mount. Personally I would describe it as a very silent computer. (I do video editing in FCPX with 4K 10 bit MXF files from a canon C300 mkII) and im connected to a 4K OLED LG C9 for a secondary monitor. It isn't silent, if I listen I can hear it, but is it annoying? Not to my ears.

In our house we have a low noise central heating pump, wich I can hear, does it annoy no. We have a low noise ventilating system - again if I listen I can hear it, but it isn't annoying. My MacBook Pro 16 (i9, 5500m 8GB) on the other hand is noisy to the point, where I just want to throw it out the window, same thing could be said (when under load) with the 2017 iMac (maxed out) I used previously.

The above do apply to my unit, I do believe that there are some difference to specific units, just as it is the case with coil whine, screen uniformity etc.
Click to expand...

I am finding my i9, 5700 XT much quieter than my 2014 MacBook Pro and also quieter than my NAS which is in the same room but not on my desk.
 
wilberforce said:
I just received my 2020 iMac replacement for my 2014 iMac (first 5K 27" model), and can make side-by-side comparisons.
Mine is an i7 with 5500 XT.
The fan on the 2020 iMac is noticeably louder and more air flow than on the 2014, when both are running at 1200 rpm (according to MacsFanControl).
On my 2014 the fan at 1200 rpm is barely audible, and I have to put my ear close to the vent at the back to hear it, and can barely feel any airflow on my hand. (It has always been like this, from day one in 2014).
On the 2020 I can just hear it from the front of the machine (in a quiet room), and can easily feel much more airflow, at the same reported 1200 rpm.
If the reported rpm is correct (1200), it seems the fan design has been somehow changed to produce more airflow, perhaps with different fan blade shape or size - I don't know.
It is still a very quiet fan, and does not bother me, but it is a noticeable change.
Something to consider for those that are very sensitive to fan noise.
IMO the fan noise when running at minimum rpm is the most important consideration for noise: this is the condition for 99% of the time.
Everything else about the 2020 iMac is a welcome improvement over the 2014 - speed, screen, etc
Click to expand...

I'll be interested in finding out if I can hear a difference between the 2017 & 2019 iMac models I've owned. I remember many complained on this forum about the fan noise of the 2017 i7 models, and I found it to be quiet machine for basic everyday tasks. These new chips can run pretty hot, so if Apple modified the fan in some way to produce more airflow it might be a good thing in the long run. Of course a second fan would've been preferable.
 
I got my iMac 2020 (i7, Radeon Pro 5500 XT) last Friday. I can hear the constant high-pitched sound, all the time, when the fans are at 1200 rpm. To be clear, the sound is not the air flow, it's a 'flutter' done by the fan spinning. It comes from the inside. I have a laptop cooling pad and the fan does the exact same irritating sound (I turn it off as soon as the MBP cools down).

Most probably I'll return it, because after some hours in front of the machine my ears start to whistle. I don't mind the air flow, but I can't stand this high-pitched sound.

I'm thinking about getting a Mac Mini + the 5k UltraFine. What do you think about the 5k monitor? I've read plenty of bad things about it.
 
I wonder if anyone has tried rigging up some sort of baffle or muffler around the vents to absorb the sound. Seems like it should be possible.
 
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