Do you have the preset set for "Low Volume Music" - as that increases frequencies at low volumes and flattens out when driven harder.
Maybe setting that to flat to start with might help the appearance of bottom end when wound up. Personally, the B1 has never appealed to me with audiences of 200 - 300.
I run two L1 M2 with a B2 each and never have to drive the output more than 50% with the B2's normally set in mid position and I'm just a vocalist.
I cannot imagine running a disco on a single B1 with any success in a room with more than 100 in it - if that.