On the fly CMYK conversion

I have been in the habit of converting on the fly (H20 and C1Ppro v. 3.5.2). However, I have noticed that when shooting black fabrics, these blacks go VERY... well black. K value is always very high- much different then shooting in RGB and converting in p shop CS.

Anyone have advice or similar experiences? Is the C1 Pro conversion just that bad? I believe all of my color settings are OK.

thanks for your help,
J.