The ornamental design for a portablespeaker, as shown and described.
FIG. 1 is a perspective view of the portable speaker showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof;
FIG. 8 is a reference view thereof showing an example of the usage of the subject design in which the subject design is connected to the mobile phone; and,
FIG. 9 is a reference view thereof showing an example of the usage of the subject design in which the subject design is connected to the mobile phone and than bent and attached to the back of mobile phone by magnetism.
The broken lines in FIGS. 8 and 9 show environmental structure only and form no part of the claimed design.