Philips monitor for Mac Mini 2014

Your Late 2014 Mac mini has two Thunderbolt 2 ports with Mini DisplayPort connectors, and the ability to double as Mini DisplayPorts. It also has a HDMI port.

It apparently is possible to connect two monitors with resolutions of up to 2560x1600 pixels (i.e., two 30"monitors, though two 27" 2560x1440 monitors would be more common), or a single monitor with resolution of 4K (at a lower refresh rate).

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Mac mini (Late 2014) - Technical Specifications - Apple Support

Video Support

Support for up to two displays at 2560 by 1600 pixels, both at millions of colors

Thunderbolt digital video output

• • Native Mini DisplayPort output
  • DVI output using Mini DisplayPort to DVI Adapter (sold separately)
  • VGA output using Mini DisplayPort to VGA Adapter (sold separately)
  • Dual-link DVI output using Mini DisplayPort to Dual-Link DVI Adapter (sold separately)

HDMI video output

• • Support for 1080p resolution at up to 60Hz
  • Support for 3840-by-2160 resolution at 30Hz
  • Support for 4096-by-2160 resolution at 24Hz

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Where to begin?

The Dell P2415Q monitor is a UHD 4K (3840x2160) pixel monitor. You say that you are currently using two with your Late 2014 Mac mini. That machine does not support driving two 3840x2160 monitors – and it sounds as if driving one monitor at 3840x2160 resolution @ 30 Hz could preclude driving a second monitor of any kind.

Thus I conclude that your Late 2014 Mac mini is sending low-resolution signals to the monitor; that the monitor itself is upscaling them using the equivalent of ugly "digital zoom".

You say that 2560x1600 is the "optimal" setting. I don't think so. A 3840x2160 monitor has a 16:9 aspect ratio. 2560x1600 has a 16:10 aspect ratio (the same as the old 30" Apple Cinema Display). If you insist on running two monitors and your Mac is incapable of generating a 3840x2160 pixel signal for one or both of them, the best that you can do is either 1920x1080 or 2560x1440.

1920x1080 would probably be the appropriate setting given the physical sizes of these monitors.

You say that you want to add an additional 27" 3840x2160 monitor. So that means you want to hang two 24" 4K monitors and one 27" 4K monitor off your Late 2014 Mac mini – a machine that does not support three monitors (of any resolution), or (apparently) more than one 3840x2160 monitor (at full resolution).

I don't see that happening.

FYI, I am using a 27" 4K monitor on a M1 Max Mac Studio. This Mac supports up to five displays: "up to four Pro Display XDRs (6K resolution at 60Hz and over a billion colors) over USB-C and one 4K display (4K resolution at 60Hz and over a billion colors) over HDMI."

In Displays Settings, I have a choice of five "UI looks like" resolutions. (I call them that since this is the name that the System Information application uses for them.)

• Retina "like 1920x1080" (Larger Text)
• Retina "like 2560x1440"
• Retina "like 3008x1692"
• Retina "like 3360x1890"
• Native 3840x2160 (More Space)

I normally run in Retina "like 2560x1440" mode, because that produces text that of the same physical size as that on a 27" 2560x1440 monitor. The human eye is sensitive to physical size. This is why publishers don't print all of their books in 2- and 3-point text even though their presses have much greater resolution than any monitor.

In this mode,

• Applications size things as if the screen had 2560x1440 pixels.
• Retina-aware applications (pretty much all of them today) draw text and photos in 5120x2880 detail.
• The Mac downsamples the contents of the 5K canvas and sends a 4K image to the monitor.

A 4K monitor has 2.25x as many pixels as a 2560x1440 one – and a Mac running in Retina "like 2560x1440" mode takes advantage of every one of them. It just uses the higher resolution to draw letter shapes more accurately and to draw photo areas in greater detail, rather than to cram more and more, physically smaller and smaller, "stuff" on the screen. The same is true of all the other Retina modes.

I do not believe that your Mac has the hardware that it takes to use Retina modes in more than a very limited way.

For a 24"+ monitor, anything less than 4K resolution isn't enough to support useful Retina modes. Your Mac can only drive one monitor at 4K resolution, and you probably would have to sacrifice your dual-monitor setup to be able to get the computer to send a 4K signal to the remaining one (over HDMI, at a low refresh rate).

So let's say that you did that.

I'm guessing that there is a good possibility that your Mac will offer to let you run the monitor either

• In Retina "UI looks like 1920x1080" mode (which would use the full 3840x2160 resolution of the monitor), or
• In native 3840x2160 mode

but not

• In Retina "UI looks like 2560x1440" or "UI looks like 3008x1692" mode – the modes that would give you the best tradeoff of text size and workspace for a 27" monitor

That's because the latter modes would require your Late 2014 machine to deal with a 5K or 6K internal canvas.

+1 Servant of Cats is spot-on on all fronts.

The 10 year old 2014 Mac mini's pathetic GPU will never make you happy running dual 4K displays.

If possible, replace the 2014 model with a 2018 Mac mini or a new M2 Mac mini.

If replacing is not possible, then you would be better off just using a pair of 1080p monitors.