uxcell Car Speaker Audio DIY Phase Tester PH Phasemeter Without CD Black;

Perfect for safely troubleshooting and testing audio systems.
This phase meter can test all speakers of all car, such as samll treble, door speakers, subwoofer, etc.
How to use the tester?
the CD with the package include 4 section test music. 
section 1: left channel noise signal
section 2: right channel noise signal
section 3:  phase test signal
section 4: same as section 3
Put it in car cd player, and play  section 1 or 2, check if left/right channel connection is right. 
Play section 3 or 4, the sound speaker will produce a fixed frequency signal, then press test button.
3 green light flash and 1 red light indicates that the speaker output is in positive phase (correct connection) ; 3 red light flash and 1 green light indicates negative phase (reversed connection).

low battery light on indicates that the battery power is low.

Note: Batterty is not included in our package.