as an experienced installer I know to NOT trust my ears for anything.
as an experienced installer I don't make assumptions based upon my ears.
as an experienced installer I cut my wire, solder it, heat shrink it and leave it.
I do NOT cut my wire, solder it, heat shrink it, switch radio on an drealise I have a single speaker out of four out of phase and that I must now go back in and rewire my ENTIRE system beucase I didn't do it properly the first time. Your right, I don't pull door trims off of cars to check for polarity. I use a book.
You my dear sir are a hack. It's installers like you that make people say that installing car audio and acc is easy and to NEVER trust an installer because they will cut your car up.
You are the sort of installer that I see cars coming in for repairs where a wire has been joined multiple times because someone can't be bothered doing it right in the first place. I like fixing your mistakes, it makes me feel better when I charge people again. I know where they will come back too. Do you work for Strathfield? JB HiFi? Autobahn?