We claim the ornamental design for the speaker, as shown and described.
FIG. 1 is the front perspective view of the speaker showing our new design;
FIG. 2 is the front view thereof;
FIG. 3 is the rear view thereof;
FIG. 4 is the left-side view thereof;
FIG. 5 is the right-side view thereof;
FIG. 6 is the top plan view thereof; and,
FIG. 7 is the bottom plan view thereof.
The broken lines immediately adjacent the shaded areas represent the bounds of the claimed design while all other broken lines are included for the purpose of illustrating portions of the speaker; the broken lines form no part of the claimed design.