M/S Technique - Simulating a Bidirectional Mic w/Two Cardioid Mics

The null of a figure-8 is 90° from the axis and the null on a cardioid is 180° from the axis. You simply cannot get a M-S using cardioid mics instead of a figure-8. Inverting won't change that fact but it will screw up the output. The closest thing to it will be to use the three mics all with the same polarity. [Edit: disproved, disregard]
 
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bouldersoundguy said:
The null of a figure-8 is 90° from the axis and the null on a cardioid is 180° from the axis. You simply cannot get a M-S using cardioid mics instead of a figure-8. Inverting won't change that fact but it will screw up the output. The closest thing to it will be to use the three mics all with the same polarity.
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Holy fuck! This is like the exact opposite of what you said earlier and completely wrong.
 
ashcat_lt said:
Holy fuck! This is like the exact opposite of what you said earlier and completely wrong.
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It's pretty much the same as below and exactly dead on right. [Edit] I was wrong both times, actually.

bouldersoundguy said:
But if you're bent on trying it you won't want to invert the polarity of a side mic, but then you also won't get the null needed to make M-S work right. It may be an interesting or useful array but it won't be M-S.
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ashcat_lt said:
Check out PJ Harvey "Rid of Me". IMO, he went way too far with the "no compression ever" thing on this one, and I always use it as an example of how too much dynamic range can be a bad thing (try to listen to it in a car without going back and forth to the volume knob at every verse/chorus transition), but it's a pretty fucking great album.

I've actually got a project I'm about to start working on that was recorded at Electrical, but I haven't even listened to a single track yet.
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Cool, was it recorded by an engineer at Electrical? Just listening to "Rid of Me" and I can see what you mean about the dynamic changes, they are quite extreme. But then, maybe PJ Harvey wanted it that way. As far as I'm aware Albini doesn't like to change the sound to suit his own tastes, he simply captures the sound of the band, and if they're happy with the results he just leaves it at that.
 
This array is like two X-Y setups merged, with the middle mic the left of one and the right of the other. I would call it a coincident L-C-R array. Inverting any mic will ruin the results like inverting one mic of an X-Y pair.
 
ashcat_lt said:
This is not the same thing at all. Two cardiod mics "back to back" like this will act like an omni, and they won't leave the null area where the mid mic is supposed to fill in. It will be some sort of stereo, but it won't be M/S. You absolutely need the two side mics to cancel out any information that they share. Doesn't matter how you're decoding the M/S.
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Holy shit, you're right! I guess there is a reason why no one does this. It's terribly confusing AND isn't going to work very well.
 
bouldersoundguy said:
This array is like two X-Y setups merged, with the middle mic the left of one and the right of the other. I would call it a coincident L-C-R array. Inverting any mic will ruin the results like inverting one mic of an X-Y pair.
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Unless you invert one of the side mics, sum them, and throw them into an MS matrix. It still won't be perfect, but it will act like an MS to a point.
 
rj-skelton said:
That's basically what I was going to do, I had hoped it was going to be that simple
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Post up your clips when you can. I'm really interested to hear what you get out of all this.

Also, be sure to check out the B3 I linked to. It's not a bad mic.
 
Farview said:
Unless you invert one of the side mics, sum them, and throw them into an MS matrix. It still won't be perfect, but it will act like an MS to a point.
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I have to eat my words and concede that it would more or less work. I was wrong, you could invert one and sum both sides then M-S process it.

I see little point since X-Y will give you pretty much everything mid-side (with a cardioid mid) gives you. Panning X-Y toward center is like lowering the side mic. If you want it wider than it is panned hard you just copy the track, reverse the panning, invert polarity and add to the mix. Turning the copy up does the same thing as turning the mid mic down. And when you have a matching (truly matched would be best) pair of cardioid mics and no figure-8 then X-Y is the rational solution. But that's just my opinion. It could be interesting to try out.
 
rj-skelton said:
Cool, was it recorded by an engineer at Electrical?
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Well, yes. Over a decade ago now. It's not like they were signed or Albini picked them out or anything. They just booked the studio and an engineer and dropped some cash. They've never actually done anything with it, and I was just going to play around with it more or less for fun, but... It turns out they didn't actually give me the individual tracks but rather just what sounds like a "faders up" rough mix that they were given. It's not great, but it does give a bit of insight into the kinds of raw tones they captured. The drums actually do sound almost finished, and very much like all those other "Albini drums".

Just listening to "Rid of Me" and I can see what you mean about the dynamic changes, they are quite extreme. But then, maybe PJ Harvey wanted it that way. As far as I'm aware Albini doesn't like to change the sound to suit his own tastes, he simply captures the sound of the band, and if they're happy with the results he just leaves it at that.
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I mean, that album absolutely rocks as long as you have the headroom and can get away with turning it up so that the quiet parts are audible and the loud parts are REALLY FUCKING LOUD. ;)

If you're looking for a bit different persepective on Albini's thing, check out any (or all) of the albums he did with my friends in Low: Transmission, Secret Name, and Things We Lost in the Fire. These really are some of their best records, and the closest to their actual live sound at the time.
 
I think I've got it more or less sorted in my mind, I'm placing two cardioid microphones on top of each other, facing opposite directions, I should be able to (more or less) simulate a figure of eight mic, IF I reverse the polarity of one of the mics.

The null point of a cardioid mic is at 180° (ideally), whereas the null point of a Figure of 8 is at 90°. So the two cardioids are going to pick up some of the same sound around the 90° mark. Those areas of the cardioid polar pattern which overlap, should cancel out (given that the polarity is reversed on one of the mics) and thus, the two mics in combination would approximate what a figure of 8 mic does. I will probably bounce these two cardioid mics into one track, and this will be my Side signal.

My Mid microphone is not a problem at all.

From there, I could process these two mono tracks as you would a standard M/S recording. Either I could put into a decoder OR just do it manually.
 
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ashcat_lt said:
Well, yes. Over a decade ago now. It's not like they were signed or Albini picked them out or anything. They just booked the studio and an engineer and dropped some cash. They've never actually done anything with it, and I was just going to play around with it more or less for fun, but... It turns out they didn't actually give me the individual tracks but rather just what sounds like a "faders up" rough mix that they were given. It's not great, but it does give a bit of insight into the kinds of raw tones they captured. The drums actually do sound almost finished, and very much like all those other "Albini drums".
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Yeah, people go to Albini because of his reputation, he doesnt need to seek clients out, they come to him. I think its because they like his attitude towards recording and the music industry in general. I do too, I have to say. For one thing, placing the responsibility of decision-making (decisions a "producer" would usually have to make) into the hands of the band makes your job as an engineer a lot easier. Plus, you're more likely to preserve whatever quirks and pecularities the band have that make them special.

I'll definitely check out those bands you mentioned though, I'm always up for reccommendations, cheers.
 
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Chili said:
Post up your clips when you can. I'm really interested to hear what you get out of all this.

Also, be sure to check out the B3 I linked to. It's not a bad mic.
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Thanks for the recommendation, I've looked at the mic online and it seems to be a good mic. The versatility of having a mic that can operate with multiple polar patterns is obviously a huge plus, and at the relatively low cost it's definitely worth considering.

I will try and post some clips of how this weird technique works out, I'm waiting on some new goodies before I try it out. I'll post once I've done it because I think theoretically, it should appoximate a Figure of 8 "Side"/Cardioid "Mid" pretty well. It would be a useful reference for anyone who wants to do a M/S recording but doesn't have access to a Figure of 8 mic.
 
Farview said:
This is a funky thought experiment. I may have overthunk it...because you actually need a figure 8 pattern in order to use this method.

Now that I think about it, there is no need to reverse either of them. The only reason you reverse the mult of the side mic is to get the back diaphragm out of phase with the front one. There is no need when you use two separate mics.
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You are over-thinking again.

If you are making a fig-8 by using two cardioid mics - the one pointing left should be normal and the one pointing right needs to be polarity reversed - otherwise you won't get a fig-8.

It will have a funny response at high freqencies due to the physocal separation of the capsules.
 
With a proper figure 8 mic in mid/side we only reverse the polarity of the right side dup because there's only a single capsule and positive pressure from the right/front creates a negative output from the fig8 mic.

If you had a positive pressure from 45 degrees front/right, it would cancel to some extent without polarity flipping, whereas the same from front/left wouldn't. (with a fig8 mid/side setup - nothing flipped)

This isn't true if we use three separate microphones.
As far as I know, you'd just point 3 mics left right and front and that's that.

The main thing that's missing from doing this, compared with an actual fig8 mic, is the desirable cancellation that happens - That's the strength of a proper mid/side setup.

TL/DR It's not mid/side with 3 mics - You don't need to flip anything.
 
Steenamaroo said:
With a proper figure 8 mic in mid/side we only reverse the polarity of the right side dup because there's only a single capsule and positive pressure from the right/front creates a negative output from the fig8 mic.

If you had a positive pressure from 45 degrees front/right, it would cancel to some extent without polarity flipping, whereas the same from front/left wouldn't. (with a fig8 mid/side setup - nothing flipped)

This isn't true if we use three separate microphones.
As far as I know, you'd just point 3 mics left right and front and that's that.

The main thing that's missing from doing this, compared with an actual fig8 mic, is the desirable cancellation that happens - That's the strength of a proper mid/side setup.

TL/DR It's not mid/side with 3 mics - You don't need to flip anything.
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You could leave all mics as they are and get a useful result (which is where I got hung up), but inverting, summing, M-S processing offers more control over the width. You're cancelling any sum information shared by the side mics and converting the two signals into one difference signal. The sum information isn't needed from them because it's coming from the mid mic.
 
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