Mac Mini (M1, 2020) with Dual LG Ultrafine (24MD4KL) Displays?

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Mac Mini (M1, 2020) with Dual LG Ultrafine (24MD4KL) Displays?

I have a Mac Mini (M1, 2020) and have tried in vain to connect two LG 24" UltraFine (model 24MD4KL) displays. I am running macOS Monterey 12.0.1.

I have connected the first display via a Thunderbolt 3 to Thunderbolt 3 connection and it works fine. I have attempted, without success, to connect the second monitor via the Mac Mini HDMI port to the USB-C port (via Apple USB-C to DV multiport adapter) on the second LG UltraFine monitor. I have also tried a Belkin USB-C to HDMI adapter and a QGeeM USB C to HDMI Adapter (4K Cable, USB Type-C to HDMI Adapter [Thunderbolt 3 Compatible]) purchased from Amazon.

I have successfully connected the MacMini HDMI port directly to a Sceptre 27" monitor to establish that the HDMI port is putting out a signal. This monitor works together with a single UltrFine monitor and I can use them in tandem but really dislike the image quality of the Sceptre monitor and want the two UltraFine monitors to work.

I have independently tested my Thunderbolt cables with both LG UltraFine monitors. I have also independently tested the UltraFine monitors. Both of them work independently with the Thunderbolt 3 cable but the other monitor always fails to work when connected by HDMI/adapter/USB-C (regardless of which USB-C port I use).

I have unsuccessfully attempted to daisy chain the monitors via Thunderbolt 3.

So, I know the following:

1) The UltraFine monitors work independently via Thunderbolt.

2) The second UltrFine monitor, regardless of the adapter + cable combination, does not work via HDMI.

3) The HDMI port is putting out a signal that can be used by the Sceptre monitor (HDMI to HDMI).

What are the possibilities left? I think the most likely possibility is that the HDMI port on the Mac Mini is not putting out enough power to turn on the UltraFine (which does not have an independent power source or on/off switch). The question then becomes, is the source of this a software (macOS Monterey?) issue or a hardware issue?

If there is anyone out there who has successfully connected two of these LG UltraFine monitors to a Mac Mini, I would love hear how you did it!!

Thanks,

Mark

Posted on Dec 10, 2021 2:00 PM

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Answer 1

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MMitchell Author

Level 1

8 points

Dec 11, 2021 10:43 AM in response to Malcolm J. Rayfield

Malcom,

Thanks for the very helpful feedback. after considering my options, I think I am going to replace one of the 24" Ultrafine monitors with the LG 24" 24UD58-B 4K UHD IPS Monitor. It has similar performance characteristics to the 24" Ultrafine and, at $296 + tax it is about ⅓ cheaper than the converter. It has an HDMI port and allows me to go from HDMI to HDMI without worrying about the conversion. I can still use the 2nd Ultrafine for my wife's MacBook Air.

I wish that the Genius Bar team knew what you have shared with me. It would have saved me a lot of frustration!

Thanks again,

Mark

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Answer 2

Dec 10, 2021 8:23 PM in response to MMitchell

The M1 Mac mini's second display must use the HDMI port. Only on display can use the Thunderbolt/USB-C ports, so daity-chaining won't work.

A normal USB-C to HDMI adapter is for connecting a HDMI display to a computer's USB-C/Thunderbolt 3 port, and will not work in reverse.

You need a 4K HDMI to USB-C converter.

'

Here are a couple:

converters-comparison-table-2

https://www.siig.com/hdmi-to-usb-c-port-4k-60hz-converter-adapter.html

The display should have come with two cables, one USB-C, one Thunderbolt 3. The Thunderbolt cable (Lightning bolt icons on the plugs) will not work with non-Thunderbolt devices, such as HDMI to USB-C converters. Use the non-Thunderbolt USB-C cable (no Lightning bolt icons).

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Mac Mini (M1, 2020) with Dual LG Ultrafine (24MD4KL) Displays?

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