Phase problems vs proximity effect

[Grotius]

I'm close-miking a grand piano with a pair of AT4033s (or, sometimes, MC012s), and sometimes I hear a hollow thumping sound in the bass. Sometimes -- but not always -- inverting one of the two tracks fixes this, implying that it is a phase problem. Is it? How does one hear the difference between a phase problem and a proximity effect (boosted bass)?

Also, can anyone tell me how to interpret the phase scope that is included with the demo version of Wavelab? Is it a simple scatter diagram? What should my stereo field "look" like in the scope?

 

[PowerCouple]

MMMMMMMM...let's see...

Hello...let me see if I can figure it out. The reason why you get rid of the Low thumping by reversing the phase of one of them is simple: cancellation. Obviously is being added to the same but reversed. But be careful because this way you are losing other frequencies too.
The proximity effect is only found in cardioid pattern mics. So you can try two things (maybe only in the Low end mic -aka left hand mic-) to solve it.

1) Put it a little further from the source. Just separate it a little more.

2) Try another polar pattern (figure 8, omni...) but be aware that the tone may change on what you record with this mic.

Mostly, grand pianos sound great with a stereo pair of PZM's or PCC's, because they will eliminate any phase incoherence that may ocurr. But after all, we are home recorders (well...I am) so play around with it untill you get it right. Do not invert the phase, because you'll be cutting some beautiful sounds from your piano, and I know that you don't want that.

WARNING!: This may be entirely wrong. I hope one of the big guys who REALLY know loads of this can answer you here .

HEY! All of you guys! you know who you are!! Help us here!

Peace...

PC

 

[DeadPoet]

not a big guy, but I heard that on the old Blue Note recordings, piano's were captured using two Neumanns; one over the piano strings, in one of the holes, the other _underneath_ and with some EQ to the latter (bass roll-off it was, I think, gotta re-check that)

--Herwig