I checked my measurements for different black inks I've tested on different papers.
On JonCone Studio Type 5 paper (baryta surface), I got the following:
Epson PK= 1.849 dMax (12.06L)
ConeColor PK= 2.107 dMax (7.02L)
After reviewing your order history, I see you bought the PK ink and cart in August of this year, so the ink is very new.
Did you shake the ink bottle before filling the cartridge?
Are all nozzles fully printing on your nozzle check?
Do you now have the full set of ConeColor inks installed, or do you still have some Epson carts installed?
Did you get these measurements by printing the Ink Separation image thru QTR's Calibration Mode (measuring pure ink from each channel)?
Please let me know, thanks~ Dana