[Harp-L] Speakers, mics and phase



Yes- even with a single speaker, there is a phase relationship between the mic and the speaker that can help to accentuate, cancel or alter feedback. Imaging holding your mic in front of the speaker, facing it. If the mic's diaphragm moving in (away from the speaker) results in a signal that pushes the speaker cone out, (think, waving both hands back and forth in the same direction) then the two are sort of "coupled" and feedback will be likely. If they move in opposite directions (think moving your hands toward and away from each other, like clapping) they have a natural phase cancellation that can reduce feedback..

Now - the fact is it matters where you are in terms of wavelengths of distance from the speaker, but for yucks I wired one of my Kalamazoo's up with a speaker-phase-reversing switch. I can get feedback in either direction but the feedback tone occurs at a different frequency if its in phase than if it is out of phase - and I can get the volume knob a little higher before feedback when the switch is in one position vs. another.




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