iMac 20" 2017 speakers' cable identification

I've found a few way to test speaker polarity but the best is with battery. Please see below or click link.

If your system is already wired and you are able to pass an audio signal from input to output, you can test speaker polarity using a smartphone app.

I recommend the Studio Six Speaker Pop App. It works by connecting the audio output of your smartphone to the input of your system. Then place the microphone of your smartphone in front of the speaker you want to test. The app will send a positive impulse out to the system and measure the polarity of the sound coming out of the speakers.

If you’re looking for a quick, free way to test speaker polarity, you can do it using the following method:

For this technique, you will need a 9V battery. DO NOT touch the terminals of the battery to the speaker for an extended period of time!

1. Place one speaker wire to the positive (+) terminal of the battery.
2. Place the other speaker wire to the negative (-) terminal of the battery.
3. Notice which way the speaker moves as you make this connection.
   1. If the speaker moves outward, then the speaker wire connected to the positive (+) terminal of the battery is the positive (+) wire.
   2. If the speaker moves inward, then the speaker wire connected to the negative (-) terminal of the battery is the positive (+) wire.

This video clip shows what you are looking for when you apply the battery to the speaker wires: