MS using 3 mics

[virtualvisions]

I'm probably missing some really basic concept thinking up this idea, and putting aside any practicality criticism (I just wanna know if this would work ) I was thinking of way to make an MS recording using 3 cardioid mics.

An MS recording with 2 mics is 1 cardioid and 1 figure 8. The left signal is the positive left mic signal, the negative right mic signal (from the negative side of the figure 8) plus the mid mic. The right signal is then the positive right mic signal, the negative left mic signal, plus the mid mic.

I was thinking, using 3 cardioid mics, one would be the mid, and then 2 other cardioid mics would be the left and the right (they would be facing away from each other at 180 degrees). The left would become the mid mic, plus the left mic minus the right mic, and then the right would just be the mid mic, plus the right mic minus the lef mict.

The only real difference would be that the right and left mic signals wouldn't be in the same space as they would be with the figure 8, so the only potential problem I can think of right now would be phase issues, but maybe if the left and right mics were close enough together it might work?

 

[ofajen]

I'm probably missing some really basic concept thinking up this idea, and putting aside any practicality criticism (I just wanna know if this would work ) I was thinking of way to make an MS recording using 3 cardioid mics.

An MS recording with 2 mics is 1 cardioid and 1 figure 8. The left signal is the positive left mic signal, the negative right mic signal (from the negative side of the figure 8) plus the mid mic. The right signal is then the positive right mic signal, the negative left mic signal, plus the mid mic.

I was thinking, using 3 cardioid mics, one would be the mid, and then 2 other cardioid mics would be the left and the right (they would be facing away from each other at 180 degrees). The left would become the mid mic, plus the left mic minus the right mic, and then the right would just be the mid mic, plus the right mic minus the lef mict.

The only real difference would be that the right and left mic signals wouldn't be in the same space as they would be with the figure 8, so the only potential problem I can think of right now would be phase issues, but maybe if the left and right mics were close enough together it might work?

Yeah, we had a thread about this a few months ago and I mentioned this option and that, in theory, this set up is equivalent to a 2-mike MS pickup, but of course you won't get quite the same results as if you had a good figure-8 pattern mike for the S. Still, if it's all you have, you might as well try it out. Good luck.

Cheers,

Otto

 

[dementedchord]

for that to work kinda-sorta i think the sides would need to be omni's....

what are you using this for???? if the room is fairly big ya might want to check out whats called a decca tree... it wass the primary method used for alotta old big productions with like full string sections and such....

 

[ofajen]

for that to work kinda-sorta i think the sides would need to be omni's....

You might think that, but you would be incorrect. If the side mikes were omnis, they would basically pick up the same signal, neglecting directionality at high frequencies. Mathematically, the omni response, as a function of angle, a, is: response = 1. So, if you take the difference of L and R pointing mikes you get 1 - 1 = 0 or total cancellation. All you would hear would be the high end information along the axes.

A cardioid is basically the average of an omni (response = 1) and a figure-8 (response = cosine(a)). The L cardioid response is, say, L = 1/2(1 + cos(a)) and the opposing cardioid is: R = 1/2(1 + cos(pi -a)) = 1/2(1 - cos(a)). So, if we take the difference we get L - R = 1/2(1 + cos(a)) - 1/2(1 - cos(a)) and the constant terms cancel and the other terms add to simply L - R = cos(a), which is the mathematical expression of the figure-8 response.

Gets confusing at times, I know.

Cheers,

Otto

 

[virtualvisions]

It wasn't intended to find out if it was practical, as I stated in the first paragraph .
And about a decca tree, it is usually used to provide an L, C, and R, and even if I were to make it stereo it wouldn't be much different than a narrow XY.

 

[punkin]

I've done it both ways...3 mics vs. 2 thinking the same thing. Sounded much different. The three mic approach sounded more like the X/Y and by the time you get the center channel blended in it was hard to distinguish the difference. In fact with the center channel, the stereo split seemed minimized. The Omni + center did sound "true", I just didn't care for how it sounded...thin to me. Could be mic selection, technique what ever...

I've tried to become "one" with the M/S technique but just don't get the appeal. To me it just sounds thin. I'm certain it's a matter of technique and application. So far I've only fooled around with it on drum kit though. I guess I haven't found how to place the mics properly yet.

 

[Marik]

I'm probably missing some really basic concept thinking up this idea, and putting aside any practicality criticism (I just wanna know if this would work ) I was thinking of way to make an MS recording using 3 cardioid mics.

An MS recording with 2 mics is 1 cardioid and 1 figure 8. The left signal is the positive left mic signal, the negative right mic signal (from the negative side of the figure 8) plus the mid mic. The right signal is then the positive right mic signal, the negative left mic signal, plus the mid mic.

I was thinking, using 3 cardioid mics, one would be the mid, and then 2 other cardioid mics would be the left and the right (they would be facing away from each other at 180 degrees). The left would become the mid mic, plus the left mic minus the right mic, and then the right would just be the mid mic, plus the right mic minus the lef mict.

The only real difference would be that the right and left mic signals wouldn't be in the same space as they would be with the figure 8, so the only potential problem I can think of right now would be phase issues, but maybe if the left and right mics were close enough together it might work?

Yes, it will work. You will need to inverse polarity on one of the "side cardioids" (that's how you get fig.8).
Strictly speaking, you will get some degration because of the shadowing effect of mics bodies and not "perfect" fig.8 (because of physical distance and not matched mics), but you still should be fine.

Best, M

 

[dementedchord]

You might think that, but you would be incorrect. If the side mikes were omnis, they would basically pick up the same signal, neglecting directionality at high frequencies. Mathematically, the omni response, as a function of angle, a, is: response = 1. So, if you take the difference of L and R pointing mikes you get 1 - 1 = 0 or total cancellation. All you would hear would be the high end information along the axes.

A cardioid is basically the average of an omni (response = 1) and a figure-8 (response = cosine(a)). The L cardioid response is, say, L = 1/2(1 + cos(a)) and the opposing cardioid is: R = 1/2(1 + cos(pi -a)) = 1/2(1 - cos(a)). So, if we take the difference we get L - R = 1/2(1 + cos(a)) - 1/2(1 - cos(a)) and the constant terms cancel and the other terms add to simply L - R = cos(a), which is the mathematical expression of the figure-8 response.

Gets confusing at times, I know.

Cheers,

Otto

hey otto thnx for the info... i was assuming the need to invert one of the sides....

 

[virtualvisions]

I've done it both ways...3 mics vs. 2 thinking the same thing. Sounded much different. The three mic approach sounded more like the X/Y and by the time you get the center channel blended in it was hard to distinguish the difference. In fact with the center channel, the stereo split seemed minimized. The Omni + center did sound "true", I just didn't care for how it sounded...thin to me. Could be mic selection, technique what ever...

I've tried to become "one" with the M/S technique but just don't get the appeal. To me it just sounds thin. I'm certain it's a matter of technique and application. So far I've only fooled around with it on drum kit though. I guess I haven't found how to place the mics properly yet.

I've always liked MS better solely for the fact that you can basically make the stereo field as narrow or as wide as you want, and you can use it in mono as well. I can see how it would sound thin for a drum kit, but for miking bigger and farther away sources like a choir or an orchestra, I would prefer MS.