I have one receiver and one subwoofer that routes high-range signals to 2 speakers.
I have 4 speakers in total.
Two front speakers and subwoofer connect to the receiver.
The two back speakers connect to the subwoofer.
The subwoofer has its own gain knob but it only controls the subwoofer, not the 2 back speakers.
The receiver volume control works on all speakers.
I need to adjust the 2 back speakers to not be so loud relative to the other speakers.
What's the best way to add this type of volume control?