JBL LSR Owner's Manual page 25

Figure E details the connections using unbalanced cable and Tip/Sleeve connections to the 1/4"
input. In this mode, the Ring and Sleeve of the LSR input are shorted by the plug automatically.
Unbalanced Source
Tip
+
Sleeve
Unbalanced Tip/Sleeve Connectors
short the Ring and Sleeve Automatically
Unbalanced Figure E
LSR T/R/S Input
Tip
+
Ring -
Sleeve
22