@wolf_garcia are you saying that you have 2 subs connected in series across the Right and Left negative speaker terminals? Such that each sub’s negative terminal is connected to the negative speaker terminal and each positive sub terminal is connected to the other, i.e. ‘joined’ by the red wire?
Or, are you ‘joining’ Left and Right Speaker positive terminals to each other before going out to the positive terminals of each sub? (I.e., a parallel connection)
Trying to figure out how you’re getting three wires to do the work of four.
Jeremiah