Problem is, the lows aren't really the issue with the UE900 --- it's relatively tight with a reasonable amount of boost, and unless someone is insistent upon getting less in the lower-mids/upper-bass, changing out the filter won't really help, and even then, the change would be limited. So, if anything needs changing, it's the mids and highs, and that's what is likely coming out of the tiny little hole.
I think we're getting ahead of ourselves here, though.
EDIT: After looking at the exploded view, they might be using the red filter for the mids/highs? Confused by the choice...
Edited by tomscy2000 - 10/2/12 at 7:50am