How to make a figure of 8 out of three cardioids

Question

Hi,

I'm making a test setup for MS recording.

The 1st setup is with a figure 8 mic and a cardioid. The 2nd setup is with a figure 8 mic and a omni. The 3rd setup would be with 3 cardioids. (2 S channel placed exactly(!) opposite and phase aligned)

I found that by panning the two S cardioid mics hard left and right and adding M did not result in the same audio perception as with a figure 8 and cardioid.

What I did to resolve this: First summing the two mics to make a new figure 8 signal. 1st S channel phase non inverted -> bus 1 2nd S channel phase inverted > bus 1

Then treat bus 1 (the 'new' figure 8 signal) as you would do normally with S signals bus 1 > new channel 3 and pan hard left, phase non inverted bus 1 > new channel 4 and pan hard right, phase inverted channel 5 has the M signal.

This results in a much better MS with 3 cardioids.

Anyone agree/disagree?

Answer 1

I went through this same process a while back when I realized that I couldn't afford a good fig 8 either. I tried every setup in the book, but in the end you really do just need a good figure 8. :)

You'll note that you're losing one of the primary MS benefits with this setup - the fig 8 mics wont cancel out when you sum to mono any more. If anything summing to mono will add weirdness. this is because you're now dealing with two capsules instead of one for that channel, and they're in slightly different physical spaces.

In the end I found that I much preferred the sound of just aiming the mics at in the different directions and calling it a day.

Answer 2

Sounds like you basically made a complicated X/Y-setting. Two Cardioids together border/crosses over to Omni as they have a very wide pattern, whereas two Super Cardioids would get much closer to a true Figure-Of-8.

Answer 3

Totally agree that a true MS really needs a true fig 8, but as a test setup, or 'cheap' MS solution, the method in the OP could do the trick though.

Answer 4

Your experiment is based on a false premise. A figure 8 mic picks up front and back 180 out of phase with the other, physically creating a perfect rejection zone to the sides. Just check out a figure 8 polar pattern.

2 cardiods back-to-back would need to be connected or mixed together with one out of phase with the other to emulate the figure 8 with the side rejection zone. Connecting or mixing 2 back-to-back cardiods in phase gives you a virtual omni, which is why it doesn't work in an M-S setup. Adding an inverted signal of the already-combined in-phase cardiods as you've done, is not the same - you just made 2 emulated omnis out of phase with each other, not a figure 8.

Here's the proper process - combine 2 cardiods back-to-back with the one pointing right flipped out-of-phase (if they're identical dynamics, you can get away with a y-cable with the right FE XLR pins 2&3 wired out of phase), designate that combined signal "L in-phase", pan L on mixer. Phase flip a duplicate of that combined L in-phase signal to generate a R out-of-phase, pan R on mixer. Add front facing cardiod panned center.

Even with the back-to-back cardiods combined out of phase with each other, because of the necessary physical spacing, they can never achieve as perfect a side signal rejection of a figure 8.

Further, many newer (I'm old) figure 8 mics use 2 capsules, each with its own diaphragm, and again due to physical spacing, though better than 2 out-of-phase cardiods, those still cannot achieve as perfect a side rejection of a ribbon figure 8, for which both front and back use the same diaphragm.

It's fine to emulate as best you can, and I sure have jerry-rigged setups when needed, but a ribbon figure 8 in an M-S setup is always the best way to go. Next choice, a 2-capsule figure 8.