The ornamental design for a speaker, as shown and described.
The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
FIG. 1 is a top perspective view of a speaker showing our new design.
FIG. 2 is a front view thereof.
FIG. 3 is a side view thereof; and,
FIG. 4 is back view thereof.
The broken lines in the figures illustrate the portions of the design that form no part of the claimed design.