Chances are, their PA system included SUBWOOFERS. Subwoofers produce only the lowest frequencies. (+/- 10-90 HZ) These are the frequencies that are "felt" more than "heard". 

The vast majority of music contains these frequencies. Unfortunately, PA systems without subwoofers try to reproduce these sounds within the same speakers that are producing higher frequencies. This causes the speakers to get overloaded, and all program content suffers, creating a harsh, unpleasing sound all around.

If you want to hear the natural resonance of the cello, feel the thump of the kick, enjoy the lower overtones of the grand piano, talk to your local PA shop about SUBS!