Roll of subs in soundstage?

When I replaced my older KEF Ref 107/2s with newer Ref 1s it seemed to improve the sound above 30 Hz a bit, but lost a sense of scale with large orchestrations. I recently reset the crossover to a pair of Velodyne HGS-15s from 40 Hz to 80 Hz, keeping the slope at 24 dB/octave. That change somehow seems to have expanded the soundstage and sense of scale with large orchestrations to match that of the 107/2s. I use an SMS-1 bass manager that provides acoustic room correction, and set the volume so I’m unaware of the subs except when a pipe organ pedal note is played. Whereas at the 40 Hz crossover setting the subs were rarely invoked, at 80 Hz they are often active. I don’t understand how that change in crossover can have such a profound effect of the perception of soundstage and scale.

I recently acquired a third HGS-15 and the SMS-1 can manage up to 3 subs, so I’m tempted to try a distributed bass setup. I have a pair of HGS-10s and a spare SMS-1, but that might be too complicated to set up.

db