Bass Amp
Duel Speaker
Phase Cancelled
Microphone
Drums
Invert Phase & Polarity
Out of Phase 180°

Reverse the Phase of a pair of speakers by switching one of the speakers wires
+- +- / +- -+

or face 2 speakers together & adjust distance intil silent.

M-Audio Microphone Pad with Phase Inverter

https://en.m.wikipedia.org/wiki/Phase_(waves)

https://en.m.wikipedia.org/wiki/Phase-shift_oscillator

Phase & Polarity