I think I get it... I was thinking that by splitting the signal and reversing polarity on one of the signals, you were somehow creating an outlet for the back of the mic that could pick up a different sound than the front side... and so when you panned the mics out, you got different sounds on the left and right channel.As I understand it now, the effect is created by the fact that a ribbon mic creates a positive voltage from the front and a negative voltage on the back.... So, after you mult the signal, reverse the polarity, and pan hard left and right, you end up withLEFT CHANNEL Middle Channel RIGHT CHANNEL (+/-) (+) (+/-) but you invert polarity and get this: (+/-) (+) (-/+)***This diagram represents the front and back (respectively) of the ribbon mic: (+/-) So, sound on the left side of the microphones will show positive voltage from the ribbon, plus positive voltage from the directional. Positive plus positive = positive. The sound will appear on the left of the stereo field because you panned one of the + mics that way. And so, if I understand it correctly, there is nothing inherently different about the signal, except for the fact that you inverted the polarity of the signal??? And so, when a sound comes from the right side of the array, the ribbon mic initially gets a (-) signal. Negative plus a positive equals nothing, so it SHOULD be quieter on the right side, right? BUT you reversed the polarity of the signal so what you actually get is: Positive plus positive = Positive, and after you pan hard right, the sound appears on the right side of the stereo field.. Excuse me for wasting so much breath on this subject... It's something I've always wanted to understand more clearly. I'm reading about the MS pair as I type here, and please, if I am very far off from the truth, please stop me before I confuse myself even more.... thanks again, trent

Dear Electrical Audio,Tomorrow I am tasked with recording a steel drum, and I wanted to make a Mid-Side array out of a Beyer M160 and a Royer r122v. I've never done it before, but I am excited to try. See, I understand the basic logistics of what-to-plug-in-where and what-button-to-press-to-invert-the-other-side-of-the-royer, and which way to pan everything, but I am afraid that I do not understand the basic mechanics of the mid-side pair.So, my directional mic is capturing the center of the source, and the bi-di is getting the left and right side, but, how? How can one ribbon element capture two unique sonic events? So to speak... As I read more about this, it seems that the left side of the element is in phase with the center mic, but then sound entering from the right is out of phase with the left, and a stereo image is created, and the engineer can control, the width, .... ??? If someone here could explain this to me I would appreciate it very much. Thank you for your time.Sincerely, Trent

I think the best way to begin to understand MS is to think about the signal as having three components which will eventually be mixed down to a stereo (or mono) signal:You have your left, your mid and your right.In your three channels of decoded MS signal, you have:- MS Left: +1 left, 0 mid, -1 right- MS Mid: +1 left, +1 mid, +1 right- MS Right: -1 left, 0 mid, +1 rightThe Mid signal picks everything up equally. The side channels only pick up the left and right components, and the right channel is just the left channel inverted.Ultimately, these get mixed down to two stereo channels:- Stereo Left = MS Left + MS Mid = (+1 left, 0 mid, -1 right) + (+1 left, +1 mid, +1 right) = +2 left, +1 mid, 0 right- Stereo Right = MS Right + MS Mid = (-1 left, 0 mid, +1 right) + (+1 left, +1 mid, +1 right) = 0 left, +1 mid, +2 rightSo you're left with a left channel which contains a strong left signal, a moderate middle single and no right signal. Your right channel contains no left signal, another moderate middle signal and a strong right signal. Added together you get a nice stereo spread.This is simplified, it doesn't work out so perfectly neatly in the real world - obviously the signal isn't split up so discretely, instead you have a gradual gradient from hard left to middle and out to hard right which will be coloured by the mics' pickup patterns. I've just set it up this way to make it easily understandable. Additionally, in this example the MS channels are level matched - in practice you can change the ratio of mid to side get a more narrow (more mid channel) or more wide (more side channels) stereo field.Once you can understand MS in a simplified, theroretical way like this, then you can start to think about the actual real-world way in which MS works, and the ways that you can start to tweak the MS signal (eg: using compression or EQ on one of the MS channels, or using a different mic in the Mid position).

Hello everybody, thank you for your timely responses! I guess the first thing that comes to mind when I'm considering my choice of side mics is weird off-axis frequency response from a non-ribbon bi-directional mic. I've seen charts of condenser mics that have switchable polar patterns, and there is always a random spike at the null point.. I'm concerned that this spike with actually sound worse than the difference between the front and back side of the 122v... I do have access to the Royer sf42.. I think I'll try that! I'm beginning to understand the mechanics of how the MS pair works, but I'm afraid that the deeper and deeper I get into the math and physics of the technique, I'm venturing into vocabulary and ideas that I don't really understand. It is mystifying to me that one ribbon element can be used to make a stereo image. So, a ribbon mic creates a positive voltage from the front, and a negative voltage from the back, right? But, when a wave-front reaches either side of the mic, first the element is pushed forward by the compressed air, and then pulled backwards by the rarefied air, right? So If that is true, then a wavefront from either side of the element would produce positive and negative voltages, right? I don't understand how one element can produce a stereo image! So it only works in conjunction with the middle mic, but, wow that is inspiring, and confusing. Either way, I'm going to go ahead and do this MS setup tonight on the steel drum. I'd be happy to post the stereo file to my soundcloud for analysis for anybody's interested. : ) Cheers.Thank you again for you time and for helping me understand this technique.From, Trent

If you decide that you like the approach, you'll want to consider a different mic for the 'side' approach. The 121 has different frequency responses for the front and the back of the mic. Thus, you'll be getting a different signal on your right vs left sides beyond what's presented in the stereo field. You'll still be able to get a good idea of how MS works with the Royer, but it will be less than 'accurate'.The M160 is often paired with the M130, which should be the same front and back. = Justin

TheMilford wrote:I often wondered how the M160 would sound with a fig-8 LDC as the Side.It sounds very good. I did this with a Gefell UM70 and it's one of my favourite drum sounds I have recorded. Unfortunately the drums were ultimately compromised somewhat by a massive wash of guitars but solo'd it sounded great.

I often wondered how the M160 would sound with a fig-8 LDC as the Side.

The link I posted at the end of this thread is a good reference. I'm afraid that thread doesn't have such sexy diagrams as this one, but I'm pretty sure M-S hasn't changed in six years.

ilovethesechords wrote:I'm beginning to understand the mechanics of how the MS pair works, but I'm afraid that the deeper and deeper I get into the math and physics of the technique, I'm venturing into vocabulary and ideas that I don't really understand. It is mystifying to me that one ribbon element can be used to make a stereo image. So, a ribbon mic creates a positive voltage from the front, and a negative voltage from the back, right? But, when a wave-front reaches either side of the mic, first the element is pushed forward by the compressed air, and then pulled backwards by the rarefied air, right? So If that is true, then a wavefront from either side of the element would produce positive and negative voltages, right? I don't understand how one element can produce a stereo image! So it only works in conjunction with the middle mic, but, wow that is inspiring, and confusing. TrentYou understand that the fig 8 mic is a mono signal right? It can't be used, by itself to create a stereo image. Think in general terms. So the front of a figure 8 mic (+) will be in phase with the cardioid mic, and the rear of the fig. 8 mic (-) is out of phase. When you sum the two mics together, you get the over representation of the left because of the common phase adding to each other, and under representation of the right, because of the out of phase information canceling out. You repeat this set up to build the right side picture, buy reversing the polarity of the side mic. When you do that the rear of the fig. 8 mic is in phase with the cardioid, and the front is out of phase. The sum builds an over representation of the right side, and under representation of the left.So, at the risk of rehashing, with the side mic pointing 90 º left from the mid-Left output = Mid + SideRight output = Mid + polarity reversed SideYou will see this written like this sometimes L=M+S, R=M-S.To do this on a console, you need to mult (split) the side mic signal, preferably post preamp, to two channels. The first channel you pan all the way to the left, the second channel you pan all the way to the right, and flip the polarity. The mid channel will be panned to the center. ImportantThe two side channels must be at exactly the same level for this to work right. You can crudely confirm this by listening to the side channels, with the mid muted, pan them to the center, and trim the fader levels until the signal completely disappears. Remember, the two side channels are opposite polarity, and should cancel completely out if summed together at the same level.You can adjust the stereo-ness by raising or lowering the gain at the Side mic's preamp (feeding both side channels). Note- Be careful that you don't have too much side level. You can easily see if this is the case by mono-ing you monitors, and listening to the difference. If the apparent loudness drops significantly, it could be because there is too much Side level (cancelled away when you mono'ed it).

You have to think of the butt as two separate items, and not as one thing.