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Solution for 2015 (late) 27" iMacs for use as Monitors with M2 Mac Mini

MacDann

MacDann

macrumors 6502a
Original poster
Mar 27, 2007
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Can see the end of the Earth from here
TLDR: I have an M2 Mac Mini Pro and some old late 2015 27" iMacs I would like to use as external monitors. What is the best option?

I have am M2 Mac Mini Pro that I currently have three monitors on - two are 30" Apple Cinema Displays being run with active DVI+ adapters. I love these monitors, but would really like to move on and retire them.

I have several 27" 2015 (late) iMacs available to me. Yes, I realize that they'll use more power, etc., than a similar Thunderbolt monitor, but they'll cost me nothing. I am familiar with the following approaches to retask an iMac as a monitor, to-wit:

  1. HDMI to USB-C capture dongle and the HDMI Monitor app. This would require me to "update" the iMacs to Ventura or later using Open Core (not a problem for me to do.) Cost: $20 x 2
  2. A "Luna" dongle. Cost $80 x 2
  3. "Duet" subscription app, but it only does two monitors total. Nope.
  4. Update iMacs with OpenCore to 15.x (Sequoia) and use screen mirroring.
I tried #4, as I've done OpenCore installs on MacPros quite successfully in the past. It works quite well, believe it or not. I'm not doing any intensive video or graphics work, so that might make it more acceptable if, in fact, the speed or resolution aren't perfect. That said, for my situation, while it will entail a little more user interaction to use as well as power, it's a no-brainer for me at this point.

I'll continue to search for more modern 27" Thunderbolt displays to replace them, but at least this gives me a working alterntive until that time comes.

MacDann
 
MacDann said:
TLDR: I have an M2 Mac Mini Pro and some old late 2015 27" iMacs I would like to use as external monitors. What is the best option?

I have am M2 Mac Mini Pro that I currently have three monitors on - two are 30" Apple Cinema Displays being run with active DVI+ adapters. I love these monitors, but would really like to move on and retire them.

I have several 27" 2015 (late) iMacs available to me. Yes, I realize that they'll use more power, etc., than a similar Thunderbolt monitor, but they'll cost me nothing. I am familiar with the following approaches to retask an iMac as a monitor, to-wit:

  1. HDMI to USB-C capture dongle and the HDMI Monitor app. This would require me to "update" the iMacs to Ventura or later using Open Core (not a problem for me to do.) Cost: $20 x 2
  2. A "Luna" dongle. Cost $80 x 2
  3. "Duet" subscription app, but it only does two monitors total. Nope.
  4. Update iMacs with OpenCore to 15.x (Sequoia) and use screen mirroring.
I tried #4, as I've done OpenCore installs on MacPros quite successfully in the past. It works quite well, believe it or not. I'm not doing any intensive video or graphics work, so that might make it more acceptable if, in fact, the speed or resolution aren't perfect. That said, for my situation, while it will entail a little more user interaction to use as well as power, it's a no-brainer for me at this point.

I'll continue to search for more modern 27" Thunderbolt displays to replace them, but at least this gives me a working alterntive until that time comes.

MacDann
Click to expand...

Option #4 is the best to me. Zero extra cost and acceptable performance.
If you have several iMac 2015, try selling them first to see how much money you could convert them to. Then you can decide what to do next.
 
Nguyen Duc Hieu said:
Option #4 is the best to me. Zero extra cost and acceptable performance.
If you have several iMac 2015, try selling them first to see how much money you could convert them to. Then you can decide what to do next.
Click to expand...
Thanks!

It's what I'm doing right now. I've run OpenCore on two 2013 27" iMacs to get them on Sequoia, which was probably overkill, but it works. I've set them both up under my account and configured them to log in automatically. The only step I have to take now is to connect both via the Displays menu and I'm good.

We'll see how well they play nicely with my LG primary display and the M2 Mac Mini over the next few days, but for now it appears to be good.

It's possible the 2013 (late) 27" iMacs could do TDM, but the M2 Mini won't, so that's a waste. Unless they would and I could just use a Thunderbolt 2-3 adapter. I've got to research this and see. Just trying to make it as simple as possible.

MacDann
 
MacDann said:
Thanks!

It's what I'm doing right now. I've run OpenCore on two 2013 27" iMacs to get them on Sequoia, which was probably overkill, but it works. I've set them both up under my account and configured them to log in automatically. The only step I have to take now is to connect both via the Displays menu and I'm good.

We'll see how well they play nicely with my LG primary display and the M2 Mac Mini over the next few days, but for now it appears to be good.

It's possible the 2013 (late) 27" iMacs could do TDM, but the M2 Mini won't, so that's a waste. Unless they would and I could just use a Thunderbolt 2-3 adapter. I've got to research this and see. Just trying to make it as simple as possible.

MacDann
Click to expand...

Check the below list as final conclusion: (requirements to connect iMac 2013 in TDM)
1. iMac 2013 27" running High Sierra (to log-in desktop screen)
2. M2 mini is outputing video through TB
3. M2 to iMac 2013 connection: TB3 to TB2 adapter + TB2 male to male cable.
 
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Nguyen Duc Hieu said:
Check the below list as final conclusion: (requirements to connect iMac 2013 in TDM)
1. iMac 2013 27" running High Sierra (to log-in desktop screen)
2. M2 mini is outputing video through TB
3. M2 to iMac 2013 connection: TB3 to TB2 adapter + TB2 male to male cable.
Click to expand...
Have you confirmed this configuration? I ask because it's one I looked at, but the cost of the adapters was steep - I want to have two monitors run this way.

I'm curious to know - thanks!

MacDann
 
MacDann said:
Have you confirmed this configuration? I ask because it's one I looked at, but the cost of the adapters was steep - I want to have two monitors run this way.

I'm curious to know - thanks!

MacDann
Click to expand...

If you are concerning about the adaptor cost, then there is no other solution for you.
For me I would just buy an LCD control kit and gut out the iMac to convert it to a 2k monitor.
 
MacDann said:
Have you confirmed this configuration? I ask because it's one I looked at, but the cost of the adapters was steep - I want to have two monitors run this way.

I'm curious to know - thanks!

MacDann
Click to expand...
Per Apple's support documents using Target Display Mode requires the other Mac be 2019 or earlier, and Catalina or earlier. And of course it would work with a 2013 iMac, but not a 2015 which is what you initially asked about (haven't read the rest of the thread, maybe you have a 2013 too).

Regardless - even with a 2013, I don't expect it would work with a Mac mini M2. And even if it works now, it could quit at any point with a software update on the mini.

I'll stand by what I said earlier - "Bad solutions and worse solutions" and get something different. Yeah, you might not get 5k for the price you're willing to spend but you could get 4k for not a lot. And it'll save you a TON of aggravation, and buying specific TB converters that have no future utility once an iMac dies.
 
In a perfect world, I would like to get a couple 27" Thunderbolt displays and use them. I've yet to determine if using an Apple TB2 to TB3 adapter would accomplish this?

I'm totally familiar with TDM and that it won't accomplish what I want in this case. I get it. I would just like to continue to have a decent-sized three monitor setup like I have now with my M2 Mac Mini, which is a bit of a kludge but it works - One "modern" LG monitor on HDMI and two 30" ACDs running off USB C/DVI+ adapters.

I've ordered an Apple TB2 to TB3 adapter to see if it will work. Should be here on Tuesday, I'll report back then. In the meantime, of anyone can confirm that a couple of 27" TB displays with adapters will work with my Mini, I'll be going that direction. In this case as I've stated I have a couple of 27" 2013 (Late) iMacs that I want to retask, if that's ot a realistic approach I'll go with 27" TB displays if I can.

MacDann
 
#4 is using the Airplay to Mac feature. OCLP enables it, even if Apple thinks that the hardware is too old.

#5 is to create a virtual display on the mini Pro, and then screen share into it from the iMac. This approach works for Macs back to at least 2007. If you need more performance, create a Thunderbolt connection between the Mac mini and the iMac. You'd need a Thunderbolt 3 to Thunderbolt 2 adapter and a Thunderbolt 1/2 cable.

This is what it looks like:
 
It is possible to convert an iMac 27" 5K model into a monitor. This requires opening the imac, ripping out the hardware motherboard and PSU etc, and install a Conversion board so you can use it as a monitor. I might do this in the future myself. There is a youtube video that show you how it's done.

 
Backslashnl1 said:
It is possible to convert an iMac 27" 5K model into a monitor. This requires opening the imac, ripping out the hardware motherboard and PSU etc, and install a Conversion board so you can use it as a monitor. I might do this in the future myself. There is a youtube video that show you how it's done.

Click to expand...

One of the downsides of this approach is that they don't have a standard fix for the speakers at this time. I have heard of people trying to get the speakers working but I don't know how successful they've been.

I have the Thunderbolt 3 cable to test out Airplay to Mac without any lag. I'd like to test it out with the 2015 iMac but I'd have to buy a few cables to test it.
 
"It is possible to convert an iMac 27" 5K model into a monitor."

@LukeMiani didn't show a 'real world' conversion, he made a quick double-sided sticky tape proof of concept YT video.
For the real world experience of how it's done visit the MR forum DIY 5K Monitor Success. :)

@pshufd "One of the downsides of this approach is that they don't have a standard fix for the speakers at this time. I have heard of people trying to get the speakers working but I don't know how successful they've been."

Very successful. ;)
Its easily done with a plug'n'play solution from AliExpress.
Or you can do it properly - which is not so easy but gives my 'very successful' result.

01interiorfull.jpg
 
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PaulD-UK said:
"It is possible to convert an iMac 27" 5K model into a monitor."

@pshufd "One of the downsides of this approach is that they don't have a standard fix for the speakers at this time. I have heard of people trying to get the speakers working but I don't know how successful they've been."

Very successful. ;)
Its easily done with a plug'n'play solution from AliExpress.
Or you cam do it properly - which is not so easy but gives my 'very successful' result.

View attachment 2458693
Click to expand...

That's a pretty interesting thread.

I'll point people there in the future. It's more work than I'd do myself but I know it's possible and straightforward now.

I wonder if anyone has started a business to turn iMacs into monitors. It should become more financially viable as prices of 5k iMacs just keep dropping.
 
Picked up one 27" TB Display yesterday for $140, pristine condition. Several others for sale in the area for a similar price but I've been unable to connect with the sellers so far. Already had the Apple USB-C to TB adapter. Plugged everything in, works great!

Now I just need to find one more...I do miss the real estate of the 30" ACD, but not the heat and power consumption.

MacDann
 
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Reactions: Nguyen Duc Hieu
PaulD-UK said:
"It is possible to convert an iMac 27" 5K model into a monitor."

@LukeMiani didn't show a 'real world' conversion, he made a quick double-sided sticky tape proof of concept YT video.
For the real world experience of how it's done visit the MR forum DIY 5K Monitor Success. :)

@pshufd "One of the downsides of this approach is that they don't have a standard fix for the speakers at this time. I have heard of people trying to get the speakers working but I don't know how successful they've been."

Very successful. ;)
Its easily done with a plug'n'play solution from AliExpress.
Or you can do it properly - which is not so easy but gives my 'very successful' result.

View attachment 2458693
Click to expand...
That's an inspiring topic! Really cool to see how far some guys have gone to create their own 27" 5k Apple monitor.
Currently I am still satisfied with the performance of my 2020 (and 2017) iMac 5k, but perhaps in a couple of years I will perform this mod myself.

I still really prefer the design of this 27" iMac, in my opinion much better than the 24" version with it's white bezels and missing front Apple logo :)
 
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