Please help me choose the QUIETEST iMac

Discussion in 'iMac' started by mountain_feeling, May 4, 2019.

  1. mountain_feeling macrumors newbie

    May 4, 2019
    Hey all,

    I'm looking to buy a new iMac to replace my current 2011 21.5 iMac. I’m sensitive to noise and want something with minimal heat issues / fan noise.

    I will mainly use this computer for web surfing, email, youtube, piano VSTs, and some gaming. A 21.5 inch screen is big enough for me.

    I’m leaning towards: 21.5 4K iMac, i5 8500, 512 SSD, Vega 20, 16GB RAM.

    I'd like to stick with a 65W processor and supposedly the Vega 20 is more power efficient (cooler?) than the other GPU option. The only thing preventing me from buying the above configuration is that the price tag is nearly identical to a 27 inch 5K, i5 9600K, radeon pro 580X, 512 SSD, 8GB RAM. Poor value perhaps and non-upgradable RAM.

    Any thoughts?
  2. mikeboss macrumors 65816


    Aug 13, 2009
    the 2017 27" base model (3.4 GHz i5) is the most quiet as far as I can tell.
  3. cynics macrumors G4

    Jan 8, 2012
    The 27" is 65w with a better cooling solution. I honestly don't know which is quieter but I have an I5-4670 in my 27" 2013 iMac and even when transcoding video the fan RARELY lifts off of 1200rpm and that is with an 84w TDP CPU.

    Matter of fact I'm transcoding a video right now.

    Screen Shot 2019-05-04 at 2.45.32 PM.png

    89c is highest core temp, 53c is GPU.

    When gaming fan increases however the game audio makes its unnoticeable.
  4. mountain_feeling thread starter macrumors newbie

    May 4, 2019
    Are the cooling systems in the 21.5 and 27 inch iMac different?
  5. CWallace macrumors 603


    Aug 17, 2007
    Seattle, WA
    Based on the teardown, they are the same general design, but the 27" does have more internal volume which could help passive cooling via the back aluminum plate.
  6. fisherking macrumors 604


    Jul 16, 2010
    ny somewhere
    this is so subjective, depends on what the imac gets used for, the processor, ram; the environment the mac gets used in. once the fans kick in, they do what they do; they come on when they're needed. the 21" should do, an i7 might be worthwhile... but (at least with the gaming), no matter what you go for... you may invoke the fans....
  7. cynics macrumors G4

    Jan 8, 2012

    I haven't seen a tear down on the 2019 so I don't know what has changed or became more similar however there is a lot of extra space to fill in the 27". In the past 5 things were obviously different.

    1, Heat pipe design and blocks they are connect to are different because the logic boards between the 21" and 27" has different layouts. So basically GPU and CPU's in different locations. This makes little difference though and that is because the heat pipe needs to be tuned for the application.

    This is a 2013 21" iMac

    Screen Shot 2019-05-05 at 3.10.34 AM.png
    And this is a 2013 27"

    Screen Shot 2019-05-05 at 3.10.46 AM.png

    Even though the block for the CPU is directly under ducted portions of the heat sink where the heat pipe needs to goto it runs out what looks to be an unnecessary length and then comes back. That is likely in insure phase change of the working fluid within. However there is likely more passive cooling in the area.

    2. The heatsink is designed with a duct that air drawn in from the bottom of the iMac is exhausted through. The 27" iMac has more depth so the duct is larger and the fins (which disperse the heat) have more surface area to do so.

    3. Similar to above the fan of the 27" model is taller due to extra depth of the 27" which makes the vanes of the blower longer meaning it can move the same amount of air at lower RPM's. For example I believe in 2013 (my iMacs year) 21" iMac fan ranged from 1400-4000rpm, while the 27" ranged from 1200-2600rpm. The higher velocity of the 21" fan combined with a more restrictive heatsink fin duct design = higher static pressure which nearly always means more noise. Comparatively speaking, this is why my 2018 MBP can have TWO fans running at 5000rpm while being very loud and still not be moving as much air as my 2013 iMac running a single fan at 2000rpm.

    4. The 27" model heatsink is typically beefier in its design due to faster (hotter) components that are available for it. You can see that in the GPU blocks pictured above.

    5. The heatsink is designed for the CPU with a highest requirements for that model (I think Apple could still do a little better at this but that is the intent). So currently the 21" heatsink is designed for a CPU with a 65w TDP and the 27" heatsink is designed for a CPU with a 95w TDP. This is the whole reason people get a less powerful CPU in the 27" iMac range for noise. They are putting a 95w TDP heatsink on a 65w TDP CPU.
  8. mountain_feeling thread starter macrumors newbie

    May 4, 2019
    Wow! Very interesting. Thank you very much for the detailed reply!
  9. WillemSleegers macrumors member

    May 2, 2016
    What kind of noise are we talking about? At idle or when under load?

    Under load it is going to make noise and I don't see why noise is an issue then. Idling noise, however, I can see being an issue because that's relevant when you actually expect things to be quiet, and it may not be.
  10. mountain_feeling thread starter macrumors newbie

    May 4, 2019
    Well, both I guess. I've heard mixed reviews about the 1200 rpm fan noise at idle. Some say it's dead silent; others say it's very noticable and annoying. Under load, I expect the fans to increase, but not to the point where the noise bothers my wife in the next room who is also sensitive to noise.

    After reading some of the replies in this thread, I am now leaning towards the 27 inch. Probably mid-tier with the i5 8600 and the radeon pro 575. Although I'd like to get the top of the line iMac, especially since the price difference is negligible, the 95W i5 9600K worries me as does the 150W 580X. Too much heat generation. It would probably sound like a vacuum cleaner under continuous load.
  11. WillemSleegers macrumors member

    May 2, 2016
    I suppose a lot of factors are relevant here and instead of trying to figure it out, I think the best thing might simply be to just order one online and if you don't like it, send it back. I've done this several times with some Apple products and the process is not too annoying.
  12. mj_ macrumors 6502


    May 18, 2017
    Austin, TX
    I've heard that for some reason the 2019 base model is supposed to be louder than the 2017 despite the fact that the cooling system is seemingly identical. Maybe new fan supplier, different fan blade material, etc. Since I only have a 2017 base model I can't comment on that but be aware that there might be an issue with the current generation.
  13. ssledoux macrumors 65816


    Sep 16, 2006
    Down south
    Have you been happy with your base model? Is it the 21.5 or the 27?
  14. mj_ macrumors 6502


    May 18, 2017
    Austin, TX
    27" base model, and I'm very satisfied so far. I tend to be extremely sensitive to ambient noise when I'm working and the iMac has been an absolute pleasure to use. I've returned plenty of systems due to what I would consider excessive noise and in the last year since I've had this iMac I have only heard it two or three times. Not because the fans ramped up but because it was so quiet in my office that I could actually hear the hard drive spinning. It's important to note that it was definitely the hard drive, not the fan.

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13 May 4, 2019