Topic: overlapping polar patterns

[Jhurlbs81]

I've always wondered this but felt too stupid too ask: What happens to a stereo recording where the two polar patters overlap?  Does it attenaute the signal in that area, increase it?  Or am I just off in left field.  Recently, my patterns have been drawn in somewhat.  I am finding for the shows I tape, (mostly clubs and theaters), that I do a whole lot better aiming just outside the stacks.  Obviously, it depends what you are trying to accomplish as I know this decreased angle will cause the image to suffer, (and this is what I'd like to discuss:)  but I find at maybe 8 inches apart with an angle around 60 degrees (or aimed just outside the stacks) i've had fantastic results!  My taste is a more direct sound I guess.  Here is a 1 minute sample where I was set-up in this configuration.  (Bisco-Hammerstein ballroom @ FOH) 

I'd like to hear your thoughts on this pattern, varied patterns in general, and if anyone could address my orignal question it would be most appreciated.

Jesse

[Todd R]

As long as things are in phase, adding two sounds together will increase their amplitude.  So where the patterns of your two stereo-mic'd mics overlap, the sound will increase.  Recognize though that when you are using a directional mic, say a cardioid, that the amplitude of the sound signal is attenuated when off axis.  So a cardioid mic facing 45 degrees left (ie, a 90 degree angle between mics) will have the sound coming from the center attenuated about 3db, as will the center of the right mic be attenuated 3db.  Then when you add them together, the left mic gets the left side of the soundfield (left stack) without attenuation since it is pointed at it, the right mic gets the right side of the soundfield unattenuated, and the two mics together create the center of the soundfield at roughly the same volume as either side by adding together the two slightly attenuated signals from the L and R channels.

2 mics run coincident (XY) will have the signals in phase, so their signals will add where the patterns overlap.  Near coincident patterns like ORTF or DIN will lead to "comb filtering" in the high frequencies where there are slight differences in phase between the two channels.  This can help soften the tendency towards stridency in mics that are of a brighter nature, and can often sound much more pleasing than running them XY.  You should be able to find more info at the Oade site or on the DPA microphone university page.

All that said, I've often liked running a modified NOS pattern with cards in bad rooms.  I don't like tightening the angle as narrow as 60 degrees due to loss of image.  But running a modified NOS with capsules 30cm (12") apart and an angle of about 75 degrees can yield great results.  Takes out a bit more of a crappy sounding room and gives a more direct sound from the stacks, but the larger NOS spacing helps preserve a pretty big soundstage, even with the reduced included angle.

[Jhurlbs81]

+T
Thanks for the info Todd.  Exactly what I was looking for.  I'll have to try that mod NOS pattern?  Any ideas on T bars to accomodate an active set-up in this pattern?

Thanks
Jesse