The ornamental design for a speaker, substantially as shown and described.
FIG. 1 is a front and right side perspective view of a speaker showing our new design;
FIG. 2 is a rear and left side perspective view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is rear elevational view thereof;
FIG. 5 is a left side elevational view thereof;
FIG. 6 is a right side elevational view thereof;
FIG. 7 is a top plan view thereof; and,
FIG. 8 is a bottom plan view thereof.
Any shading and cross-hatching are not features of the design but are utilized to illustrate the surface contours of the speaker design in the drawings.
The broken lines shown are included for the purpose of illustrating the unclaimed portions of the article and form no part of the claim.