The ornamental design for a loudspeaker, as shown and described.
FIG. 1 is a perspective view of a loudspeaker showing the new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a side elevational view thereof;
FIG. 5 is an opposite side elevational view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The dot-dash broken lines represent bounds of the claimed design, while all other broken lines illustrate portions of the loudspeaker; the broken lines form no part of the claimed design.