Double Bass Stereo miking out of phase to reduce feedback?

[Jaygetsreal]

I recall someone a few years back advocating miking double bass with a stereo pair of microphones to achieve a fuller sound for both recording and live. Can't find the thread now but it seems to work nicely.
But my question is about feedback. if you invert one of the mics' phase in the preamp would that reduce feedback? I am assuming the stereo signals are passed separately to the desk and your stage speaker/monitor just receives a mono mix of the two.
I haven't tried it yet but might try it if the theory says it will work. TIA

 

[DoubleMIDI]

By inverting the phase of one of the ORTF-mics (or any other mics where the membranes are rather close to each other) you almost cancel the signals out, specially in the lower frequencies.
Not a good idea.

By placing two mics in a distance you get phasing, at least in some frequency regions.
It would get better if you place a lot of mics or pickups distributed over the vibrating object as the different phasing will get back closer to the acoustic radiation of the object.

BTW, you might get a similar effect to the mono-mixed ORTF-mics by using a single omni mic. Probably even better than that.

 

[AGCurry]

I don't see a good case for using stereo mics on a bass for live performance; when recording, there's typically no feedback to reduce unless you're monitoring through speakers.

Phase switching is typically used for live performance when you're playing through an amplifier, when you need to put the amp's output out of phase with the instrument. But that's monaural.

 

[DoubleMIDI]

For reducing feedback either go with a contact mic or shield the mic against speakers which contain the bass signal.

Theoretically two highly directional mics pointing in opposite directions to the bass and the amp, close to the bass, possibly one of them phase inverted, can reduce feedback, but it might not work in practice as the sound gets colored and the feedback rejection is small and only works in some frequency regions, depending on the distances.

BTW, a wide cardioid mic pointing to the neck would have a similar characteristic as the ORTF-mic you have shown in a mono mix.