[cyberspyder]

I've always relied on the red dots, is there a better way?
 
Brendan

 

[nikongod]

For testing phase (left to right errors) you can use a mono tone and your ears. If the tone is right in the middle, your drivers are in phase. If the tone is "floaty" "indistinct" or "hazy" (deliberately wire a set of headphones out of phase and play a mono tone. You will know it in an instant) your drivers are out of phase.  
 
Phase (left Vs right) is CRITICAL for success but its easy to test for if your ears are functional. Polarity is not critical (prove any audibility with DBT. pwned.), but people like to fap over it all the same. If you want to check polarity, you need a polarity testing tool.
 
For testing polarity (whether the driver moves towards or away from the listener on a positive pulse) you need tools. You can buy a simple polarity test tool for about $100 from pro sound shops.
 
Worthy note: there are quite a few places and reasons that a system may flip polarity... If it really bothers you you should have phase switches in your system to correct on the fly. If they are true phase switches (left and right controlled independently) you can correct "wall of sound" recordings too.

 

[cyberspyder]

I was under an impression that it could've been checked using a DMM. Anyhow, specifically headphone drivers, any chance of damaging it if the wires are reversed? I've seen cases where it you flip the wiring, no sound comes out etc.
 
Thanks, Brendan