Mac Mini late 2018- Connect three external displays

[afilopou]

Well community, I need your help. I have two LG 27UQ750-W + 1 × LG 32UN880K and a Mac mini Late 2018 (macos 15). Until now, I have connected the two 27s with apple’s thunderbolt 3 cable (thunderbolt bus Mac mini to type c input in the display). Now I am trying to add the 32 through HDMI (from the display) to HDMI in the Mac mini. Nothing happened.I know that I’m doing something wrong and I would like to ask for your help. Is it feasible to connect all these monitors without eGPU?

I read that I must first connect the 32 monitor with HDMI to HDMI (enable the HDMI Deep color in the display menu) and then connect the two 27s through thunderbolt bus (mac mini) to USB-c (display).



Thank you very much.

 

[afilopou]

The other option is to connect each of the two 27s with usb type c (mac mini bus) to DP (display) cable and the 32” with hdmi to hdmi. The third option is to connect each of the two 27s with USB type c (mac bus) to hdmi (display) and the 32” with hdmi to hdmi.

Any idea to avoid buying cables?

 

[joevt]

Switch the HDMI cable with the one from your TV? I think you must have more than one HDMI cable in the house.

All three of your displays support HDMI. Did you try connecting one of the LG 27UQ750-W to the HDMI port of the Mac mini? Or try connecting a TV to the Mac mini?

 

[afilopou]

As a first step I will reset the SMC, PRAM and NVRAM and try to connect only the 32” with hdmi to hdmi. I am hoping the hdmi port of mac mini isn't faulty.

 

[Bigwaff]

If your LG 27UQ750-W are using greater than 60Hz refresh rate when connected, you will need to connect the LG 32UN880K first. The LG 32UN880K is max 60Hz and this will force the others when attached to negotiate a supported refresh rate, probably 60Hz as well.

 

[afilopou]

Thank you all. As already stated here, I have to first connect the 32 with hdmi to hdmi (I did a forced reboot) and then I attached the other two 27s through thunderbolt to type C.
Note: I initially did a reset of the SMC, PRAM and NVRAM and after attaching all the displays I executed the sudo pmset -a sleep 0 displaysleep 0
Note2: with this setup and in order to keep all the displays working after a shut down or a reboot, the resfresh rate of the two 27s” must be lowered to 30Hz. I am going to check, if I connect the two 27s with usb c (mac thunderbolt bus) to hdmi (display) can resolve the issue of lowering the refresh rate!

 

[afilopou]

Well, I don't like the final result but the solution is the installation of windows through boot camp. All three displays are booting normally without hiccups. Unfortunately macos cannot handle the situation as it can't maintain the 30hz of the two 27s (after a shutdown it reverts the two 27s to 60hz and the hdmi isn't working). Using windows I don't see any behaviour like the reverting of refresh rate. Bottom line: mac mini will be used with win11.

 

[Bigwaff]

Bottom line: mac mini will be used with win11.

Interesting as your Mac mini specs indicate your set up should work:
Up to two displays with 4096 by 2304 resolution at 60Hz connected via Thunderbolt 3 plus one display with 4096 by 2160 resolution at 60Hz connected via HDMI 2.0

Have you tried changing the two LG 27UQ750-W display onboard settings to reduce or set refresh rate specifically to 60Hz?

 

[afilopou]

Interesting as your Mac mini specs indicate your set up should work:
Up to two displays with 4096 by 2304 resolution at 60Hz connected via Thunderbolt 3 plus one display with 4096 by 2160 resolution at 60Hz connected via HDMI 2.0

Have you tried changing the two LG 27UQ750-W display onboard settings to reduce or set refresh rate specifically to 60Hz?

There is no option to reduce the refresh rate from the onboard settings. Maybe when toggling off the hdmi ultra hd deep colour but this affects the hdmi connection.