We claim the ornamental design for a soundbar, as shown and described.
FIG. 1 is a front perspective view of a soundbar;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is a rear perspective view.
Shading in the drawings is provided to indicate surface contours only and is not a claim for color, as the solid lines define the article for which ornamental design is claimed. The broken lines in the drawings depict portions of the soundbar that form no part of the claimed design.