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Cooling in the new 2020 27" iMac?
- Thread starter miretogo
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hoping compare two next couple days imac pro to imac fan noise post findings
You can use Macsfancontrol and set it to what ever RPM you want
or you can use istat menus once it gets updated for the 2020 iMacs
Sorry to hear this. I have a 2020 27-inch i7. I work in a fairly quiet environment and sit about 20 inches away from the screen. During the day I can't hear the fan, given the slight ambient noise. When I'm working at night it becomes barely audible, but I have to listen for it. I do notice what I would describe as a subtle "flutter" when the fan starts up after waking from sleep (an audible muffled clicking). It lasts only briefly while the fan spins up to 1200RPM. Do you experience this also?
Yes I’ve heard that noise
You don’t need super hearing. 1200rpm is crazy fast and it’s not far from your head. On my PC I run my fans at 500rpm and only use over 1000rpm when doing intensive tasks.
I have posted a summary of my research with the help of other forum members: https://forums.macrumors.com/threads/recent-27-imacs-are-not-silent.2218800/post-28783538
No. The best move it is to put heat the the edge of the system and then blow the heat straight out of the enclosure. The fan being on the other edge of the enclosure means your heat source would have to be more inside the enclosure than the fan.
What Apple has is two heat pipes that move the heat to two radiators just inside the exit vent and blow the air over that radiator ( heating the air) and then out of the box. Far better to have the fan upstream of that. The pipes will radiate a bit before get to the edge but CPU and GPU are sizable so "everything" can't be under the vent.
As long as willing to make lots more noise (more air mass moved per square inch per second. ) what is there should scale up. And if the connection feeding the heat pipes are more efficient ( more heat easily moves to the heat pipe ) , then heat will end up on the enclosure edge.
iMac Pro has a larger vent. The CPU and GPU radiators can be displaced a bit from each other ( each getting "half" of the larger exit vent). The two fans pump twice as much air. Can more move air at a slower speed through a bigger hole ( offset slower speed with more stuff. ).
A big fan at the edge is only more effective if have left most of the heat somewhat randomly scatter the internals and now have to try to capture and blow it out of the box. That is closer to cleaning up the mess after the fact. Have already let the heat wander off and impact other internal parts.
The fan's primary job isn't to "cool" the air. It is the move the air. Hot air is just plain bad. Want to get rid of it as quickly as possible. How the hot air is cooled by something outside the system is something else's "problem'. Inside the enclosure just want to get rid of it.
The fixed conduit for the fan's direct exhaust to the radiator and exit vent also are all about movement, not immediate cooling. Farther away doesn't make much of material difference to air speed if don't let other stuff get in the away or let the air wander off path.
I too have a seemingly more audible fan in my 2020 27 inch i7. And if I listen to within 6 inches of the RIGHT side of the screen and to the BACK, I can actually hear almost like a "fluttery" higher pitched noise while it idles at 1200 RPMs. This is NOT heard on my 2017 27 inch i5 3.8 at the same locations and is beginning to to make me wonder if the fans are inherently loud or if I have a bad fan.
Can someone with a 2020 27 inch iMac listen behind their unit and to where the right speaker outputs sound closely to see if they can hear what I hear? Sounds crazy but if you have sensitive hearing and you work in a very quiet environment, some sounds can be very irritating. Thanks, folks!
Can someone with a 2020 27 inch iMac listen behind their unit and to where the right speaker outputs sound closely to see if they can hear what I hear? Sounds crazy but if you have sensitive hearing and you work in a very quiet environment, some sounds can be very irritating. Thanks, folks!
I have the late 2014 iMac 5K, 4 GHz i7 CPU, 32 GB RAM, Radeon R9 M295X 4 GB, and my fan continually runs at ~2900 rpm. Several have said they managed to lower speed and temps by cleaning the air vents--any tips on doing that (without opening the case) other than just use a vacuum cleaner (when iMac is turned off)? They don't appear to be superficially dirty or clogged--but I've never specially cleaned them or anything...<G>
Thanks!
Thanks!
If your fan is constantly going full blast at idle or light loads, then something is wrong whether it is dust build up or something else. If it is dust, given it is enough to cause the fan to go full out, probably need to open it up. Blowing air in will just blow the dust everywhere inside the machine. Vacuuming probably won’t help either.
Yep, kinda figured it was something HW, as cleaning things didn't do any good. I have the 2020 27" iMac on order...<G>
Thanks!
I set up my new 2020 27" iMac a couple days ago (it's a 3.3GHz 6-core 10th-generation Intel Core i5). In my quiet home office this morning, I could hear the fan....at idle. It wasn't necessarily that loud. I'm sure for many it would be fine. But not for me. This iMac is supposed to replace a late-2013 iMac which is DEAD QUIET, all the time. Since the 2013 iMac still runs quite well (and I have a newish Mac Mini in another room), my plan is to hold onto the old iMac and return the new 2020 iMac (and wait to see what Apples does with Apple Silicon). If the 2020 iMac was quiet at idle I might consider keeping it, but since I can hear the fan noise when it's at idle, it has to go back. Too bad... seems like a nice machine.
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I've already made peace with the fact that all of the more recent iMacs have noticeable fan noise at idle. For some reason the 21.5" models seems to do better, but isn't really worth buying since it didn't get the Comet Lake treatment. I think I'll buy a 2020 iMac anyway for its performance boost and nice 5K LCD and hold on to it until Apple comes up with their ARM iMacs. Shouldn't lose too much money in the process and I guess I can live with the noise for a year 
I thought I could live with the noise, but it's very irritating trying to relax while reading some documents with the fan whirling away constantly.
Unfortunately, I too will be returning my 2020 also. My 2017 is markedly quieter in my home office. The 2020 somehow just sounds course and loud in comparison. I had them both side by side and so it was a fair comparison. I had no idea that there was such a big difference. I guess you can put me in the camp of those who have very sensitive hearing.
Thanks to everyone for the info. This confirms I'll keep my 2013 iMac going (via SSD boot) as unless I'm rendering in HandBrake then I generally have no fan noise (occasionally FCPX). Doing audio including recording in the same room as the iMac (not ideal I know but needs must) means any fan noise wouldn't be very welcome!
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.
Theres not a single fan or other device running inside the office, its a bedroom inside my house. I literally have my ear right up to the front of the iMac and I cannot hear any noise whatsoever. I'm far from deaf, so not sure what to tell you.
There’s always a possibility that Apple sources fans from multiple vendors and some of us got out of spec case fans. I’ve owned several iMacs over the years and the 2020 was the loudest by far. Most were just gentle background white noise which was downright pleasant. Not so much the one I’m returning!
I don't think it's a variation of fan specs. I've owned 2x 27" iMac 2017, tested & returned 2x 27" iMac 2019 and 1x iMac Pro 2017 all made at a different time and I was able to hear all of them at idle (however one of these iMacs was really noisy so that one definitely had a bad fan).
My experience is also consistent with the chart I've posted above using Apple's own statistics (the 21.5" 2017 being the most quiet, which I've also owned!).
So @CheesePuff, either I'm just unlucky to have had 5 iMacs with bad fans (very unlikely) or your hearing is not as good as mine or you have some noise in your room or your surroundings that masks the noise of the iMac (maybe a street close by, maybe wind noise) (I find that more realistic).
"Gentle white noise" is still noise. Having owned that 21.5" 2017 iMac I've become accustomed to complete silence. My current MBP 13" 2019 is also completely silent. You can imagine how surprised I was when I first turned on the above mentioned iMacs next to my 21.5" model. I really thought they had defective fans.
My experience is also consistent with the chart I've posted above using Apple's own statistics (the 21.5" 2017 being the most quiet, which I've also owned!).
So @CheesePuff, either I'm just unlucky to have had 5 iMacs with bad fans (very unlikely) or your hearing is not as good as mine or you have some noise in your room or your surroundings that masks the noise of the iMac (maybe a street close by, maybe wind noise) (I find that more realistic).
"Gentle white noise" is still noise. Having owned that 21.5" 2017 iMac I've become accustomed to complete silence. My current MBP 13" 2019 is also completely silent. You can imagine how surprised I was when I first turned on the above mentioned iMacs next to my 21.5" model. I really thought they had defective fans.
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Damn.
You would be screaming in pain, holding your head in your hands next to my compute server with 2 3-fan GPUs and 8 Noctua fans running full blown next to me ... which I've been working 12-14 hours a day next to it for the last 9 years.
If you want complete silence, get a passively cooled, severely under clocked (and under performing) PC.
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I will say is I have always heard the fan in my 27” iMac’s. I heard the fan on my 2013 and 2019 when at idle. Now if there was any other white noise such as air blowing from the HVAC vents, etc it would drown out the noise from the iMac’s fan. But if there was no other source of white noise, I could hear the fan. The 2019 isn’t any louder than my 2013 was when the fan was the only source of white noise.