One more question :
Does it matter the wire connecting a speaker and amplifier is black-black and red-red? What if they are connected black-red and black-red? My wires are laid in a sealed ceiling. I can't tell if the points are black or red.
Red is plus, black is minus. If you connect the wires wrong, the sound well not be great.
It we’ll be out of phase. Therefore usually terminated wires from the shop are label plus and minus.
Then connect plus to plus on both amplifier, speakers. Same with black.
If the wires are not terminated as above. You need to use bare wire, or connect the wires with banana plugs. The banana plugs are label red and black.
If the wires are laid in the ceiling, there should be easy to see which is which.
You can decide this your self. As example if one off the wires is designed differently.
As example round design, ridge. This could be red or black. Then you do the same on the other end,
If the wires are difficult to tell apart. You simply need to mark one off the wires with black tape.
As I said it’s pretty easy once you get the hang of it.