The ornamental design for a portablespeaker, as shown and described.
FIG. 1 is a front view of a portable speaker, showing our new design;
FIG. 2 is a rear view thereof;
FIG. 3 is a left side view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a top plan view thereof;
FIG. 6 is a bottom plan view thereof;
FIG. 7 is a front view of embodiment two, of a portable speaker, showing our new design;
FIG. 8 is a rear view thereof;
FIG. 9 is a left side view thereof;
FIG. 10 is a right side view thereof;
FIG. 11 is a top plan view thereof; and,
FIG. 12 is a bottom plan view thereof.
The broken lines wiring and control knobs portions in FIGS. 1-12 are included to show unclaimed subject matter only and form no part of the claimed design.