recently purchased both of the above. when connected and switching on (startup) one of the monitors flashes on and off (unstable) the other black screened. The connections i'm using is usb-c from monitor to MacBook pro. After a number of minutes, in most cases, both monitors connect.........soooo frustrating!!! what the **** is going on??? spoke to both LG and Apple and neither had a clue!! Any help please?
MacBook Pro 14″, macOS 15.3
Those 34WR55QK (I could not find 555) are 4K displays (3440 by 1440) with the bottom half missing, and 10 bits/color HDR capable. They must meet the same requirements as full 4K displays.
inputs include HDMI, DisplayPort, and USB-C.
At those data rates, you MUST have high-spec cables shorter than 1 meter
USB-20 trademark or higher for modern USB cables
(HDMI cables must be ULTRA certified, and can can be slightly longer). PREMIUM HDMI cables are slightly lower spec, but will NOT suffice for 4K at 10 bits/color.
Don't count on the cables "shipped in the box" to have any features except MAYBE the correct connectors. These are often "lowest bidder" cables.
Those 34WR55QK (I could not find 555) are 4K displays (3440 by 1440) with the bottom half missing, and 10 bits/color HDR capable. They must meet the same requirements as full 4K displays.
inputs include HDMI, DisplayPort, and USB-C.
At those data rates, you MUST have high-spec cables shorter than 1 meter
USB-20 trademark or higher for modern USB cables
(HDMI cables must be ULTRA certified, and can can be slightly longer). PREMIUM HDMI cables are slightly lower spec, but will NOT suffice for 4K at 10 bits/color.
Don't count on the cables "shipped in the box" to have any features except MAYBE the correct connectors. These are often "lowest bidder" cables.
Which specific LG monitors are these?
Which chip do you have in your MacBook Pro – a plain M4 chip, a M4 Pro chip, or a M4 Max chip? I believe that even the plain M4 chip can support up to two external displays, but it still might help to identify the configuration.
My understanding is that recent versions of macOS do not like to see any transmission errors and will deliberately cut resolution or even signal when they see errors.
I have no way of telling how good or bad your cables are, but it seems at least possible that your cables might be the source of your misery and that higher-quality cables that aren't too long might resolve the problem.
are your cables labeled CERTIFIED or have a USB trademark {SuperSpeed plus, USB-20, USB-40, USB-80} on on both ends?
If not, try obtaining a different high spec cable as a test.
You could also connect one of your displays with a DIRECT ULTRA HDMI cable (NO adapters). At around 4K, that setup has slightly more bandwidth than USB-C, so would support higher refresh rates at 10 bits/color.
I think that would be 144 Hz HDMI as opposed to USB-C supporting only 60 Hz.
ncon64 wrote:
They advertise two screens attached to this model without any suggest one might have to get a particular type of cable other than a usb-c …
I'll send the Macbook back on the premise I've been sold an experiment!!!
The fact that USB-C cables vary considerably in capability and quality does not mean that you've "been sold an experiment"!!! USB-C is a connector that can support many things – and a standard for making them coexist if several are present. That's it. It's not a guarantee that every piece of USB-C equipment supports every possible capability.
This is not an Apple thing. It's a USB-C thing. It extends not just to ports, but to cables.
At the low end, there are USB-C cables that just support 5V power transfer and that do not support data transfer at all. There are cables that only support data transfer at USB 1.0 and 2.0 speeds. Then, at the other end, there are Thunderbolt 4 and Thunderbolt 5 cables that are built to handle very high-speed transfers – and can handle just about anything you can throw at them. Cables suitable for USB-C (DisplayPort Alt Mode) fall somewhere in the middle.
ncon64 wrote:
....x 2 LG ultra wide screens (34") 34WR555QK-BL
If Mr. Bennet-Alder is correct, and the model number has only two '5's, those would appear to be these:
LG 34WR55QK-B – 34" UltraWide™ WQHD HDR 10 100Hz Curved Monitor with USB Type-C
34" monitors with a resolution of 3440x1440 pixels, a 100 Hz refresh rate, and support for 10-bit-per-channel color ("HDR10").
They have DisplayPort, HDMI, and USB-C (DisplayPort) inputs. They can deliver up to 65 watts of power to a computer. (If offered several power sources, your MacBook Pro would only charge from one, but would pick whichever one had the highest power rating.)
Use an external display with your MacBook Pro - Apple Support mentions M4 MacBook Pros but does not say that you can get refresh rates higher than 60 Hz on any port except the HDMI port. So I don't know if the Mac would negotiate 100 Hz links to these monitors or 60 Hz ones.
For what it's worth, 3440x1440 pixels @ 100 Hz would be almost exactly the same amount of data as the more common 3840x2160 pixels @ 60 Hz, so a USB-C (DisplayPort) connection presumably has enough bandwidth that the Mac could support the former (if the hardware/software is there to do it).
what cables did you buy, exactly?
which display is connected with which cable?
Thanks for your input. To answer:
Thanks
....the issue is booting up from cold or sleep mode - that's when the instability occurs. It's almost like it's searching and trying to communicate when eventually they do connect / re-connect (takes approx 2mins, on average). when all up and running, I have no issues.
thanks for your response...
55 is correct (typo).
Regarding cable length etc, why don't Apple suggest / inform all which cable size and spec is suited for all married up monitors......? leave it to the customer to trial and error.....!!
Hi all,
Does anyone have any suggestions on type and brand of usb-c cable I should purchase with the above info taken onboard please? it seems to be all confusing for me and Apple sold the MacBook well but not kept up with compatibility issues, etc......or even suggested the right / only options available.......frustrating!! i guess an apple usb-c lead should solve the issues??
Thanks....to be quite honest, i've lost the will to live!! Apple lure you in to a false sense of security in purchasing the new pro macs as it was exactly what i wanted - ability to finally attach two screens via ucb-c port without having to close the lid....we, the customer shouldn't have to be working out what leads suit.....They advertise two screens attached to this model without any suggest one might have to get a particular type of cable other than a usb-c, allow connection to my screens via usb-c.........leaving it to the customer to have to search which leads are the correct ones for all to work. not everyone who purchase apple is an expert in the filed of computers! Classic Apple sales pitch, whilst being conservative with the reality of making sure the customer's experience is not seamless !!
I'll send the Macbook back on the premise I've been sold an experiment!!!
"it works great with very expensive Apple Brand displays" my point exactly.... whilst they're at it, why not extensively test on expensive other brands?? as most users out there won't be able to purchase the "very expensive" Apple displays.They should be honest and just say, 'only works with Apple displays' and the rest of our customers, who decide to purchase our very expensive Laptops, can work out what fits for themselves! ...one dimensional!!
Who says that Apple doesn't test with other displays? But I doubt that they test every Mac with every possible third-party display on the market. There are too many of them.
By the way, I am writing this on a Mac that has a third-party display …
....x 2 LG ultra wide screens (34") 34WR555QK-BL
Thanks
Based on what we all know, any recommendations on cable make and spec please?
Thanks all!!
Macbook pro M4 to two LG ultra wide monitors
