If you’re still confused at everything I just said, here is a video showing this effect (around 2:10 mark). Notice how when given a positive DC, the cone moves out. All you need to do is to setup your system as so.
Personally I wouldn’t recommend a DC battery for obvious reasons - it wouldn’t work as we are testing the phase of the entire system, not just the speaker cabling.
And the even more obvious reason, feeding a constant DC to the coil will damage the speakers. Do not even attempt to do this if you have no idea what you’re doing. Notice how quickly he did the test? Do not even try this at home.
The speaker pop test is the only safe way to go (thanks again Don!). Also, I do not recommend running this speaker pop test for long periods, who knows if you’d melt or burn out the speaker if you do this continuously?
Personally I do not run this test for longer than 10 seconds, and I tend to wait around 60 seconds between each 10 second est.
Do not hold me liable for any damages. Do this at your own risk. So far the best tool I know of is Speaker Polarity from Studio Six. Unfortunately this requires a iPhone and is a paid app so Android fans (like me) are out luck.
For better or worse, there are DACs out there with safety features built in that detects the presence of DC and cut its output. Unfortunately if you are using DACs like these you’d need to find another way to find the phase of your audio setup (ears are a good tool).
Sure you can always use another DAC to get this test track playing, but you’d never know the phase of your DAC.
What about those “in-phase, out-of-phase” test tracks from audiophile CDs? Maybe they’d work for you but they all sound the same to me. From what I can hear, they are telling you if both speakers are in phase, or one of the speaker is out of phase, but it’s relative to the speaker. The speaker pop test, will tell you the phase relative to the signal - feed a positive pulsed DC, you get a speaker cone that can only move forward.