Audio Systems: Query

Question
Is it safe to use single Behringer Eurolive VS1520 PA speaker(150watt)in bridge mode with Crown XLS 1500 amplifier which generates 1050Watts of power.

Answer
I don't see why not.  The speaker you have is 8 ohm impedance.  The amplifier is rated to drive a 4 ohm load in bridge mode.

HOWEVER, there is no advantage in doing so.  In order to obtain the maximum out put from the amp into the speaker it should be impedance matched.  The Crown is nominally an 8 ohm output and matches nicely with an 8 ohm speaker. If you bridge the amps and are still connected to an 8 ohm speaker the power delivered will remain the same.  

If you paralleled two Behringer speakers that would make a 4 ohm load; then connecting the the Crown in bridge would allow for full power delivery.

Hope this helps.