If you can setup a band shell or something similar behind the speakers I believe the sound would be much better. Almost any "indoor" speaker would benefit from the sound reinforcement such a device would provide.
And don't forget to have some waterproof tarpaulins at the ready in case of sudden inclement weather...
-RW-
And don't forget to have some waterproof tarpaulins at the ready in case of sudden inclement weather...
-RW-