HP LD4210 42-inch LCD Digital Signage Display - Manual (Page 17)

Connecting the speakers (sold separately)
1. Mount the speakers onto the display.
Figure 3-7 Mounting the speakers
2. Use the four Taptite D3 x 12 mm (0.47 in) screws to secure the speakers to the display.
Figure 3-8 Securing the speakers to the display
ENWW Connecting the speakers (sold separately) 9