I claim the ornamental design for a speaker, as shown and described.
FIG. 1 is a front view of the speaker according to the claimed design.
FIG. 2 is a rear view of the speaker according to the claimed design.
FIG. 3 is a left side view of the speaker according to the claimed design.
FIG. 4 is a right side view of speaker according to the claimed design.
FIG. 5 is a top view of the speaker according to the claimed design.
FIG. 6 is a bottom view of the speaker according to the claimed design; and,
FIG. 7 is a perspective view of the speaker according to the claimed design.
The broken lines seen on either side of the bottom of the claimed design in FIGS. 1, 3, 4, and 7 represent unclaimed lines on the surface of the speaker, while the remaining broken lines shown are included for the purpose of illustrating the unclaimed portions of the article; all broken lines shown form no part of the claim.