Digital BW, The Print

Highlights and shadows don't show any banding at all, but the midtones are gently banded.   
It's not horrific and as casual prints they're ok, but nowhere near display quality.  Nozzle 
checks are OK.

Last night I was wondering if it was just a consequence of BO - incomplete surface coverage 
from not using the "color" print heads.  As I write this I also realize that I didn't check the 
head alignment.  Is BO printing particularly sensitive to head alignment? (Seems possible, 
but...)

I'm just wondering if anyone else has similar experience or thoughts on the cause of the 
banding.  Thanks! -b