The ornamental design for a loudspeaker, as shown and described.
FIG. 1 is a top front perspective view of a loudspeaker showing our new design;
FIG. 2 is a bottom rear perspective view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a right side elevational view thereof;
FIG. 5 is a rear elevational view thereof;
FIG. 6 is a left side elevational view thereof;
FIG. 7 is a top plan view thereof; and,
FIG. 8 is a bottom plan view thereof.
The broken line grid pattern shown in FIGS. 1 and 3 represents a loudspeaker grill; the broken line openings in the sides of the loudspeaker shown in FIGS. 1, 2, 4 and 6 represent handle openings; and the broken line structure on the rear angled corner of the loudspeaker shown in FIGS. 2 and 5-8 represents the back of an electronic package for the loudspeaker. The broken line structures form no part of the claimed design.