Dual monitors - one must be thunderbolt?

Discussion in 'MacBook Air' started by twisted-pixel, Mar 26, 2016.

  1. twisted-pixel macrumors 6502a

    twisted-pixel

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    San Jose, CA
    #1
    Hi,

    I've been trying to find an answer to this but not been able to..it might be due to interpretation though.

    I have a 2013 macbook air to which I connect an external monitor via a Thunderbolt to HDMI Converter. It's just a basic 22" monitor. I would like to add a third monitor, but obviously I will need a thunderbolt hub.

    However, when reading through the specs etc on adding a third monitor, they all say that the second one needs to be a Thunderbolt one. Now, I'm not sure if that is because most hubs only have one HDMI output (for Monitor 1) and that just leaves the Thunderbolt port available for Monitor 2.

    Can't I just connect Monitor 1 to the HDMI port on the hub, and then connect Monitor 2 to the Thunderbolt port via a Thunderbolt to HDMI converter?
     
  2. boast macrumors 65816

    boast

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    #2
    You can think of it as being only 1 display signal per thunderbolt link.

    So out of the Thunderbolt hub you can only have 1 display signal coming out. You will need either a second thunderbolt hub or a desktop hard drive like a LaCie with two thunder-bolt ports. Then you can attach your thunderbolt adapter out of this hub/hard drive, and now this SECOND chained link can power your monitor.

    Yes, it's silly that each thunderbolt device can only extract one display signal out.
     
  3. JeffyTheQuik macrumors 68020

    JeffyTheQuik

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    #3
    Forgive my confusion, but isn't that still two video streams coming out of one Thunderbolt link?

    ..........Monitor.......Monitor
    ........A....|....B.......|
    Mac -> Hub -> LaCie
    (Forgive the periods... MacRumors will compress the spaces. Please just pretend they're spaces.)

    The hub has one monitor coming out of it, and the LaCie has one monitor stream coming out of it, but doesn't the Mac have two streams coming out at Point A? I guess, looking at it, it looks like the Hub does as well to the LaCie and to the Monitor too.

    Again, I don't know the ins/outs of Thunderbolt, so this may be a misconception on my part.
     
  4. boast macrumors 65816

    boast

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    #4


    The hub can carry multiple display signals, yes, but it can only extract one to a monitor.
     
  5. noisycats macrumors 6502a

    noisycats

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    #5
    For my second monitor on a 14 Air, I use a usb to hdmi converter. It works reasonably well provided I don't tax that monitor; I keep my email, messages, and whatnot there. The other monitor is driven by the thunderbolt (via a dock with hdmi out). If you have thunderbolt monitors, I <believe> you can daisy chain them.
     
  6. JTToft, Mar 27, 2016
    Last edited: Mar 27, 2016

    JTToft macrumors 68040

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    Aarhus, Denmark
    #6
    Actually, StarTech has just recently launched a Thunderbolt 2 Dock capable of outputting to two DisplayPort displays with resolutions up to 2560x1440 on each. This would be the ideal solution to your problem.
    I've not seen any reviews of it yet, unfortunately.

    https://www.startech.com/Cards-Adap...ations/thunderbolt-2-laptop-dock~TB2DOCK4K2DP

    EDIT: Alright, looking at Amazon.com reviews, which, across four reviews, average about 1 out of 5 stars, perhaps this dock is a bad choice.

    (I'd also just like to correct some terminology: The HDMI adaptor you have is Mini DisplayPort to HDMI, not Thunderbolt to HDMI (which is impossible).)
     
  7. twisted-pixel thread starter macrumors 6502a

    twisted-pixel

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    #7
    ok...so now I think I understand...you can only attach a single monitor to each node, where the hub is considered a node. So I connect the hub to my Thunderbolt port on my macbook and connector a monitor the hdmi port on the hub, then I connect a second hub to the Thunderbolt port on the first hub, and a second monitor to the HDMI port on the second hub. hmmm..ok...expensive way to get two monitors since the hubs are $200 a piece
     
  8. JeffyTheQuik macrumors 68020

    JeffyTheQuik

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    #8
    Thank you for clearing that up for me.
     
  9. Boyd01 macrumors 68040

    Boyd01

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    #9
    I also have a 2013 MBA and since I use final cut pro a little, it would be nice to have two external monitors. I looked at all the options a couple years ago and came to the conclusion it wasn't practical, I don't want to buy a thunderbolt monitor (or two). I retired a few years ago and only do occasional jobs, but if I ever get serious about video again, I will buy a new computer that fits purpose better. :)
     
  10. UnlikelyLass macrumors newbie

    Joined:
    Mar 28, 2016
    #10
    You do not need two hubs, although that will work.

    What you need is one hub and a thunderbolt device with a pass-through -- ie, two thunderbolt ports.

    This allows you to do:
    1. MacBook -> Hub via thunderbolt
    2. Hub -> Monitor via HDMI
    3. Hub -> Thunderbolt device
    4. Thunderbolt device -> Monitor via DisplayPort adapter
    This totally works. It can be slightly less expensive (or more expensive) and does have the advantage of giving you a mix of devices instead of two hubs.
     
  11. JeffyTheQuik macrumors 68020

    JeffyTheQuik

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    #11
    Is there a limit to the monitors that I can use (other than the TB Hub limitation, not sure if 4 or 5 is the limit...)?

    Say, I wanted to do this:
    ............................................4K Monitor 2..4K Monitor 3..4K Monitor 4..4K Monitor 5..4K Monitor 6
    ......................................................|................|..................|.................|................|
    4K Monitor1----5K Retina iMac-----TB Hub1-----TB Hub2-----TB Hub3-----TB Hub4-----TB Hub5

    Other than the CPU limitations, doesn't the video card have to do the processing?
     
  12. UnlikelyLass macrumors newbie

    Joined:
    Mar 28, 2016
    #12
    AFAIK, you are still limited by the video card in whatever computer you are doing this with.

    I believe with early MB Airs, for example, if you plugged two external monitors in, the built-in monitor would go black. I have a 2015 MBA and I can plug in two externals using the above mechanism and use the internal as a third with no issues. I have not tried three externals (I don't have the right equipment all in the right place to try it) -- it depends on how many video signals have been encoded into the thunderbolt data stream.

    Even though I can "drive" three monitors (one being my internal monitor), that doesn't guarantee that the MBA actually can or does put all three of those signals into the thunderbolt data stream. I may be limited to two external monitors. Or the internal monitor may go blank when I put on three externals. I'm not sure what the upper limit is, but I'm confident that one exists and it's more than two, at least for the two MBAs I have access to. =)

    HTH!
     
  13. JTToft macrumors 68040

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    Aarhus, Denmark
    #13
    - Yes. You'll be limited both by the graphics capabilities of your machine and by the bandwidth limit of the Thunderbolt 2/DisplayPort 1.2 interface the machine is equipped with. Officially, as per Apple specifications, it can drive two 4096-by-2160 displays. However, Apple has been known to understate the capabilities of their machines. The Mac Pro, supposedly, supports three 4K displays. I'd certainly expect the iMac to handle no more than the Mac Pro, so three is probably the maximum you could do regardless of dock configurations. But I'd estimate the actual number to be two due to the 20 Gbps limitation on each Thunderbolt port. 4K UHD 60 Hz generally requires more than 12 Gbps, so I doubt one port would drive more than one - at least at 60 Hz.
     
  14. BrettApple macrumors 65816

    BrettApple

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    Heart of the midwest
    #14
    I don't think I've seen this mentioned, but there is a product out there for this kind of purpose.

    The DualHead2Go Digital ME, or other variants. I've got one that I've used on various MBPs and MBAs over the years to hook up 2x 1080p monitors and it worked pretty well. It'll also work with 2x 1920x1200 ones as well.

    [​IMG]

    Great option for pre retina MBPs too.
     
  15. Boyd01 macrumors 68040

    Boyd01

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    #15
    I have read about these, they have been discussed pretty extensively here in the past. It turns both monitors into a single virtual screen, which might be good for some applications. Wouldn't do what I need for Final Cut pro however, as it needs a dedicated separate screen for the canvas.
     
  16. twisted-pixel thread starter macrumors 6502a

    twisted-pixel

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    #16

    ok..thanks..that would work yes.
     
  17. JeffyTheQuik macrumors 68020

    JeffyTheQuik

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    Charleston, SC and Everett, WA
    #17
    Just a follow-up...

    I am running (currently, until I get my next 4K monitor):

    2014 5K iMac (at 3840x2160 using RDM) TB1 -> Upstar M280A1 4K 3840x2160 60Hz using DisplayPort 1.2
    ...........................................................TB2 -> Moread (TB->DVI/15 pin/HDMI converter) -> 15pin->Hannspree HF225 at 1920x1080

    Running X-Plane at 14.2fps. The window dimension is approximately 9500x1080 (I used RDM to make the Hannspree monitor think it was 3840x2160, and I lose about 4 fps to 10.5 fps):

    It looks good, and it does what I want it to do.
    Mind you, this is done in a Cessna T337, not an SR71 at Mach 4.

    One other thing... The Upstar monitor was running at 60Hz when my Mac thought it had two 4K monitors hooked to it.

    (The Upstar was used, and the last person that had it set it all funky... I found the reset on the menu, and voila! it worked! Not bad for a $89 4K monitor, shipped for $85 from Hawaii... OK, that's a fun story...
    I was looking for this monitor, as it is the cheapest 4K monitor out there, and I found one on Sears Outlet for $89 in Hawaii, but you have to go in store to pick it up. Well, I call one of my wife's best friends, and she lives 10 miles from the store, so I buy it, she picks it up, and spends a week figuring out how to send a monitor back stateside. UPS wanted $60 to box it up, and $110 to ship it. She didn't want to do that... So, eventually, she just made her own box, and shipped it for $85, and now I have it! Another side note... I love that sending money to people is easy now with banks making it easy and free.)

    Back on topic... I had the converter hooked to HDMI to the monitor, as I know that the converter works, so the Mac thought it had two monitors hooked to it, and when the reset happened... I'll show the steps:
    1. Buy Mini-DisplayPort 1.1a cable at Fry's (Fry's didn't have the 1.2 cables in Renton)
    2. Attach monitor to Mac Monitor goes to sleep after 5 seconds, no picture, no lights on monitor.
    3. Try to get to menu. It's in French, and my High School French didn't cover monitor menus in 1983. Goes to power saving mode, regardless of whether I'm in menu or not. Frustrating.
    4. Send e-mail to Upstar, and they open tomorrow (this was Tuesday Night) at 9:30
    5. Attach HDMI cable to HDMI 2 input (there are two HDMI 1 2.0 and HDMI 2 1.4) using converter box shown above, now attached to Hannspree monitor in the diagram at the top of this message.
    6. Monitor flashes, no picture. Press menu button, navigate to language (the menu stays on, though), switch to English (High School English classes did have monitor menu navigation in 1982...). Play around with input selection, still no picture. Mac did recognize there was a monitor there, though. (This is the point where the Mac has "two" monitors, as one was attached to Thunderbolt 1 via Mini DisplayPort cable, and the other to the converter box.)
    7. Finally give up on correcting the previous owners' settings, and Reset the Monitor through the menu.
    8. That did it! Oddly, the monitor menu looks different now. Oh well, when you get a win, you don't complain.
    The funny thing about the reviews, and I'm biased, because I like having a $170 4K 60Hz monitor, but where I have it, I don't mind the glossy finish, and no dead pixels that I notice, and the aluminum at the bottom kind of (but not really, it's brushed, not matte) matches the Mac.
     
  18. Boyd01 macrumors 68040

    Boyd01

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    #18
    Trying to understand how this relates to the MacBook Air…. Sorry, maybe I missed something?
     
  19. JTToft macrumors 68040

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    Location:
    Aarhus, Denmark
    #19
    - The MacBook Air only has one display output (a Thunderbolt port). Hence you have to do all sorts of stuff if you want to hook up two non-Thunderbolt monitors.
     

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