FIG. 1 is a perspective view of an audio speaker showing our new design; FIG. 2 is a front elevational view thereof; FIG. 3 is a rear elevational view thereof; FIG. 4 is a top plan view thereof; FIG. 5 is a bottom plan view thereof; FIG. 6 is a left side elevational view bottom plan view thereof; and, FIG. 7 is a right side elevational view thereof. Portions in broken lines are for illustrative purpose only and form no part of the claimed design.