Stupid question

What Achilles said, and to add to that: The thing you don't want to do is hook one speaker one way and the other speaker the other way. Then when one is pushing the other is pulling, hence "Out of phase."
Hooking both "black to black / red to red", is 100% the same as hooking both "black to red / black to red"

Inverted phase?
Sucking out?

I believe you guys are making that stuff up.

If it starts smoking you have it backwards, or there may be some other problem.

Try it. Any one speaker guitar or bass amp...hook it up backwards and it sounds bad. Period.

I believe you, Wolf_garcia. I've heard it myself in my friend's miswired mid-fi stereo. (He heard it too.) I'm just at a loss to explain why it matters.
BTW, I'll see if I can run your experiment on my bass amp this weekend.

Can't speak to bass amps.
I'm talking stereo speakers.