Hm. a few things you might try:
1) print a non-color managed black square of 0,0,0 to see how dark the 3800 prints under whatever paper setting you're using. Maybe try a few paper settings.
2) assuming its dark enough have a profile made. I've only had my isis for about a week but I could give it a try.
3) I've found that both my colormunki and my isis read glossy super dark regions better than matte. It seems that they can't tell the difference between ultra-dense matte colors that my naked eye can. My solution is that for some of my profiles I coat the test chart prints even if I dont intend to ever coat final prints. This seems to solve the problem of blacks blocking up for me.
Presumably the reason #3 works is because light scatter is reduced allowing the instrument to properly measure the difference between blacks which would normally be obscured (at least to the instrument) by light scatter.
I complained loudly to x-rite for a while about this problem and they claim to have fixed it in the colormunki software released last week. Interestingly it does in fact appear to be working better now even without the coating. My suspicion is that they 'fixed' it by throwing away the ultra-dark readings in some cases and just using a heuristic to guess how they should approach 0,0,0. I bet that previously the generated profile never reached 0 because it measured say 16 to be just as dark as 0.
Please Help! I am trying to achieve rich blacks on enhanced matte paper off of my 3800. I cant seem to get the shadow detail I use to get with my 2200 using the matte driver, matte ink and matte PK profile. Obviously the old profile was operating on the assumption I was using photo ink but, I was using matte ink and my blacks were really popping and the detail in the shadows was awesome. I have been working with Chromix for a profile but no luck in achieving this. If anyone has any advice or can offer a profile, I will gladly pay. Attached is an image of the 3800 Chormix deep color profile and the 2200 matte pk profile.