:Is this something to do with good pro sound drivers,having high gauss strength?
Nope all speakers have gauss strength. Otherwise you have a de-magnitized magnet. The stronger the magnet the better the transient response, and correction from overshoot.(speed if you want to call it that.)

:What does a higher gauss strength mean?
A stronger magnet.

:Is there any relation to BL?
Yep, this is where the magnet and V.C. come into play.

HTH
Bill W.