If the main concern is sound reflecting off the ceiling, then either dampen it with some form of acoustic treatment, or get a loudspeaker that is specially designed to reduce vertical dispersion. Consider something like this:
http://www.daytonaudio.com/index.php/epique-cbt24-line-array-speaker-system-pair.html
There are plenty of alternatives. Do some research on line array loudspeakers.
http://www.daytonaudio.com/index.php/epique-cbt24-line-array-speaker-system-pair.html
There are plenty of alternatives. Do some research on line array loudspeakers.