Polarity wierdness

[rchilcott]

I have my Digi 002 rack wired into a patchbay. This is my first time testing the system, however, when looking at my meters there is definately some polarity wierdness that I'm not sure how to explain. Maybe my mic setup (SR30s in XY) is just too good and the stereo image is amazing... or my system is just messed up. Let me know what you think.

System with "ambient" sound


System with piano playing


System with piano playing


Polarity reversed on left channel and piano playing


Polarity reversed on left channel and piano playing


Obviously the with the polarity reversed, the correlation meter is out of control, the mid is showing almost nothing and the side is showing too much

When it is polarity is not reversed, I feel that it is too mono. Is it just because of the XY and is this normal? I may just be worrying for nothing.

Thanks everyone for being here. I've been lerking here for months and this is my first post.

~Ricky Chilcott

[Yannick]

What are you measuring/recording ?

The piano ? Your playback system ?
What is the angle between the mics, did you pan them fully ?

[d_fu]

Originally Posted by rchilcott

When it is polarity is not reversed, I feel that it is too mono. Is it just because of the XY and is this normal?

Up to a point, yes. Depends on the angle, the distance to the source, etc. I don't see anything in your pictures that strikes me as extremely unusual... XY and other coincident techniques can sound more monoish than others..

Daniel

[Yannick]

Yes, but if this is a real piano in a not so huge room there is something wrong.

If this is a monoish piano recording playing on speakers in a good mix room, than all seems fine.

[rchilcott]

What are you measuring/recording ?

I'm measuring the recording of a piano in a smallish recital hall. It seats about 150 people if that gives you an idea.

What is the angle between the mics, did you pan them fully ?

The angle is near 90 but may be 75 or 80(can't rember 100%). Distance is about 10 ft above and 20 feet way from piano. (This is a semi-fixed installation). The mics were panned hard left and hard right.

I don't see anything in your pictures that strikes me as extremely unusual...

Ok... I'm just checking... do you think ORTF would help a bit?

[Yannick]

OK. With ideal cardioids at 80 degrees, your pickup angle is over 200 degrees (!), so at a distance of around 7m in a diffuse/quite dry surrounding this is what you can end up with : almost mono.

This is a case where MS (cardioid mid at equal level to the side mic = two cardioids in XY at 180 degrees !) or Blumlein (pickup angle of only 70 degrees) or ORTF (pickup angle of around 100 degrees) come in.

So, yes ORTF would help quite a bit, but in this case it would still sound too narrow.
20 ft seems quite far in such a small hall. I'm surprised you end up with such a narrow image - is this hall VERY dry ?

[rchilcott]

Tonight or tommorrow I will take some pictures and take some real measurements. I wouldn't say that this hall is really that dry. It doesn't have a very long reverb time, but it isn't dead. I don't think it is the wireing, because it it works or it is way out of whack. So.. again, I'll post some sound clips and some real measurements. Thanks again.

~Ricky Chilcott