I I'm asking how that is possible when the Eco-Sol ink set is the standard 4 color-process (CMYK).
The simple answer is that cartridge based inks, in particular the Epson ink set (as well as most of the 3rd party ink sets I have looked at) are not 'process-color' CMYK. They build in an extended gamut to help fill the gap of spot colors used in 'process-color' press work to product a wider range of colors than 'process-color' CMYK
But I now see why the Roland is able to produce much better looking color than the Mutoh by adding in the LC & LM inks.
The Roland Max ink is the same Epson ink as the Mutoh Eco Ultra.
So the color gamut of the ink itself is exactly the same.
lc and lm are just dilute versions of C and M and add no gamut what so ever.
They are used with larger droplet heads for smoothing.
The DX5 heads in the ValueJets, Mimakis and Rolands use a small droplet size for this smoothing.
RIP software's convert any document you throw at it to CMYK data. Therefore it can process any data, and make it printable.
RIPs typically convert to L a b color space.
And output to 4 color (labeled CMYK) to the printer.
It is actually the image color space along with the profile (including rendering intents) that ultimately determines what gets printed how.
So if you have an expanded color space that is larger than process-color CMYK, and you design in process-color CMYK, you've clipped a great deal of color out of the process that you will not get back.
On the other hand, if you design in RGM, you will be clipped to the profile gamut as demonstrated in the gamut picture I posted. A much larger gamut.
Of course, all depending on your profile, rendering intents, and color managment workflow.
Putting a RGB document into a RIP that's converting those values to the closest CMYK values is putting a lot of "hope" when you need to be "sure" what your going to output. You never know what the translation of that color is going to become in the output and 9/10 it produces "dull" & "muddy" looking values of what the CMYK color should look like.
The RIP does not convert to the closest CMYK values, it converts through the profile, to the closest gamut position of the ink set based on rendering intent. Again, larger gamut gives you color outside the process-color CMYK.
This is perhaps the biggest reason profiles for the same machine and media are different for different ink sets. None of these 'digital' ink sets are process-color CMYK, and there is no widely accepted 'standard' being used.
Of course there can be translation issues, based on rendering intents, profiles and color workflow, but those can still exist in CMYK designed artwork.