I claim the ornamental design for a woofer, as shown and described.
FIG. 1 is a perspective view of a woofer showing my new design;
FIG. 2 is a left-side view thereof;
FIG. 3 is a right-side view thereof;
FIG. 4 is a front view thereof;
FIG. 5 is a rear view thereof;
FIG. 6 is a side perspective view thereof;
FIG. 7 is a top view thereof; and,
FIG. 8 is a bottom view thereof.
The broken lines depicting a plurality of controls and/or connectors in FIGS. 5 and 6 are for illustrative purposes only and form no part of the claimed design.