Input linking and M/S (mid/side) Matrixing. When and in what type of recording situation would either of these options be used. My SD 633 offers this option. Maybe it's one of those things I'd never or rarely use.

"Input linking- Input pairs 1-2 and 5-6 can be linked as stereo pairs. Inputs can be linked as a standard stereo pair or as an M/S matrixed stereo pair."

Linking pairs is handy when recording true stereo signals (as for music production) So you can adjust levels in both channels simultaneously. And so that if you are using limiting or compression, etc. it affects both channels equally.

Mid-side is a stereo micing technique where you use a cardioid micropohone facing forward for the "MID" signal, and a figure-8 microphone facing sideways for the "SIDE" signal. When you listen to the Mid or Side signal "raw" it makes little sense to your ears/brain. It takes special signal combination to recover a "Left" and "Right" audio channel by doing M+S for one side and M-S for the other side.

As you say, they are features you are unlikely to use for the kinds of production you seem to be doing.

Thanks for that Richard.

I remember seeing this type of mic configuration at some performances in the theater, and always wondered why there was a front facing mic and one to the side.

As you said, probably won't be doing to much of that. But got me wondering: is the "side" mic facing the main "mid" mic, or is it aimed stage left? and wouldn't there be a third mic facing stage right? Or is the idea just to give the recording "ambience" with the one additional mic.

And if that's the case, wouldn't recording two seperate channels do the same thing and then mix in post? I'E. "Mid" mic channel one, "Side" mic channel 2?

You have a great weekend kind sir!

Jonathan

Rather than re-explain it here, I suggest you simply google "m-s microphone" and you'll find a wealth of information.

Thanks Greg, I'll do that.

Also there is mention of this in Jay Rose's "Producing Great Sound..." Probably some youtube stuff too.

Have a great weekend all.

JL

is the "side" mic facing the main "mid" mic, or is it aimed stage left?

The whole point of a bi-directional (or "figure-8") microphone is that it is EQUALLY sensitive on BOTH sides. One side is "in-phase" and the other side is "opposite-phase". So you could say that it is aimed "stage left" AND "stage right".

This kind of microphone is rather different from the kind of mics we typically use for video production. Although sometimes people use M/S in video production where they use the "Mid" microphone for the main dialog pickup, and the "Side" microphone (multiplexed with the "Mid" signal) to add some stereo ambiance. But that is quite a tricky thing to pull off properly, and to make it worth the expense and extra production effort. More of a "laboratory curiosity" IMHO.

Indeed the Mid and Side mics are recorded separately AS-IS, and then re-constituted back into L/R stereo in post-produciton mixing. The MS feature in your SD mixer (and other brands of gear) lets you re-multiplex the M and S signals so that you can MONITOR what is happening in L/R stereo, the signals still remain separate Mid and Side on the recording.

Excelent Richard!

I get it now, bi-dirtectional that is. And I get the placement.

So I'm going to go out on a limb here.

You may recall I'm the one who has the AT 822 stereo mic that I was driving everyone nuts with all my questions. Could you technically use a stereo mic for M/S recording, since it has two distinct sides, as a bi-directional mic? In fact, is a stereo mic actually a bi-directional mic or the other way round, or a whole other can of worms?

Thanks again.

Jonathan

No. While the AT822 may (or may not) be using M/S technology INSIDE, the microphone, it only OUTPUTS the "Left" and "Right" signals. It does NOT output "Mid" or "Side".

Now, some stereo microphones (such as my Shure VP-88) are specifically designed to output EITHER the matrixed "Left" and "Right" signals, or (at the user's selection) to output the "Mid" and "Side" signals.

I use an M/S mic all the time but it outputs L+R so is easier to record, as others have said the M/S set-up is worth researching and dolby pro logic surround is also based on the M/S type set up.

M/S mic's can be very useful as the M or mono mic is always pointing towards the action so they can be easier to use and keep stereo imaging, adjusting the S signal can also narrow or widen the image and we even had an M/S control on our AMS Neve Logic and DFC consoles so you can adjust the width of an A/B or left and right signal.

You can also get plug ins for pro tools etc that will allow you to do a similar thing and this one is for free: Brainworx bx_solo - Plugin Alliance (http://www.plugin-alliance.com/en/products/bx_solo.html)

Thanks guys> I found this YouTube video interesting as well:

Mid-Side Microphone Technique - YouTube

Jonathan,

Let's differentiate between "mic" and "element." A conventional single-channel mic has one element. A stereo mic has [at least] two elements inside the single housing. And a few newer, esoteric shotguns have multiple elements with very specific phase spacing to enhance the pickup pattern.

A bi-directional element is open front and back. By definition, that means it's either a ribbon or a condenser, because you can't make a dynamic that is open in the back (that's where the voice coil and magnet assembly are located).

A classic example of a bi-directional mic is the old RCA BK44 studio ribbon mic, which contains just a single ribbon element (and its impedance matching transformer).

Positive air pressure at the front of a bi-directional element produces a positive output voltage; positive air pressure at the back of the element produces a negative output voltage. Air pressure arriving exactly 90º off axis (for example, arriving at a "side" element, directly from the "mid" direction) should produce no output voltage, because the pressure will be exactly equal at the front and back of the "side" element.

A "stereo mic" might actually be M/S, or it might have two cardioid elements pointed in some unspecified directions, roughly left and right of center. (Some of the hand-held recorders that claim to have "stereo" mics actually have a pair of omnis. IMHO that is NOT a stereo mic because the spacing is very close, and there is only a very tiny difference in phase between the two channels, producing a signal that is virtually mono except at higher frequencies.)

I've actually looked inside an AT822. It is definitely NOT an M/S mic. It has two condenser capsules (presumably cardioid), one angled (~45º) left of the mic's central axis, and one angled (~45º) right of the central axis.

One advantage of a true M/S mic is the M element pointed straight forward, which can be used for dialog; the 822 has no such "forward facing" element.

The 822 outputs left and right from the two capsules; there is no M/S output option.

Of course if one wants to, one can use audio software to produce (L+R) and (L-R) channels, and then reduce the level of the (L-R) channel, and finally matrix back to L and R. That will reduce the stereo spread.

However, the matrixed signal described above is NOT the same thing you would get with a true M/S mic, because there is no nice clean centre (M) channel, and the pickup patterns of two cardioids are not the same as the patterns of a true M/S mic.

If you want a half decent low cost M/S mic check out the sony ECM-MS957 it is what I have used for nearly 20 years to record sound effects for TV. The ECM-MS907 is also a handy budget M/S mic and both output A/B but have a 90 and 120 degree width adjustment.

http://www.manualslib.com/manual/161401/Sony-Ecm-Ms957.html

I've been recording almost exclusively M/S with my SD 702 for years and the recording is L/R stereo, not a mid track and side track, although that option is available by not linking the tracks.

From the User's Guide:

"If MS stereo linking is selected for inputs, program sent to tracks and headphones will be L/R stereo program. To record discrete M and S signals, do not link for MS, but monitor the MS signal in headphones."

Other recorders or mixers may of course differ.

Since I started this thread last July (2015) I thought I'd give you guys an update. This week the M/S bug bit again when i found something on youtube that clearly demonstrates the effects with and with out M/S and quiet honestly, I was really amazed.

The sample I heard was from someone playing acoustic guitar with and with out the M/S effect (for lack of a better word). I had to try this out.

Spent a lot of time learning about mic placement, and channel configuration in Logic X. Here is what I did:

At least one of the two mics I used were probably not suited for this, more likely the side mic which from what I understand needs to be a "figure 8" or receive sound from both the front and rear. But they are the mics I own and I thought just for laughs... For my mid mic I used a Rode NTG 3 shotgun (supercardiod) and for the side mic I set up my Rode NT 3 (cardiod). I also have an old Beyer Dynamic short shotgun that I could have used, but not sure that would have been any better than the NT 3. And lastly I have (don't laugh) Audio Technica 899 lav (omnidirectional) I could have tested, but didn't have time.

I carefully place mics as close together and in the proper direction per everything I had seen.

Both mics feeding into a Sound Devices 633. From what I learned I linked the two inputs for both mics together.

On the 633 you actually have a headphone preset that processes M/s so you can here some of what is going on. I recorded some acoustic guitar to Wave Poly,Even though Inputs 1+2 were linked, I still ened up with a mid track and a side track.

I then set those up in Logic. Two tracks, mid and side. I then duplicated the side track and phase inverted that track and paned it hard right. I panned the original side track hard left.

I linked the two side tracks, and then, wait, it's coming.......holy crap. How cool is that! Even with my probably awful set up! The stereo effect is amazing!

Now I realize that I would have been better of just recording straight into my M-Audio Fast Track to Logic because of the gazillion options for sound alterations. But i thought I'd try this on the SD first. The recording is very dry, and obviously there are not really any tone or EQ adjustments. Just not really made for this I think.

So there you have it.

Any thoughts welcome. But I find that for recording a single instrument at least, this is really quite remarkable, and I may poke into this further, but seems like I'd have to invest in at least another mic which could collapse my marriage.

Jonathan

You can likely produce all manner of unusual phenomenon by unconventional mic placement, mixing and phase-combining. But what you are hearing isn't really "M-S" Neither of the mics you used is really suitable to produce the orthodox "M-S effect".

I agree with Richard and a shotgun is probably the worst type of mic to use for M/S but there again I did an ITV stereo sound course and they said a lav could be used as the M signal and a boom mic as the S content!

Whatever works in the real world but you must make sure your mono signal is OK but as the M content should always be the key sound source it should be OK.

There were all sorts of phase enhancement processes brought out over the years including Q sound and one from Roland, you also find that some synth stereo keyboard patches are heavily M/S processed to create large width but if you mono them they nigh on fully cancel out !

The best M/S combination tends to be a forward facing cardioid and a figure of eight mic for the S content. I used to have a nice little combo from beyer of a M201 and a M130 as it didn't need phantom power and was good for generic sound effects recording but I then switched to the self contained sony M/S mics like the ECM MS-957 etc as they output A/B which is more convenient to record but you still have a width control that is more fixed and stable.

Where I work now we have the digital soundfield microphones (ex Calrec) but they are very very expensive.

As a kid in the 70's I used to play around with surround before I even knew what it was by hooking up two sets of stereo speakers to my hifi and putting the ones behind me out of phase to give a pseudo surround set-up.

Thanks Richard and Gary.

As I continue to look into this, I found that maybe my shotgun (Rode NTG3) may not be the worst choice. This from B&H website:

"As far as capturing your MS recording, you only need two mics and two tracks to record. One mic must be bi-directional (figure 8 polar pattern) and the other is most often directional, or cardioid pattern, although Alan Blumlein described using an omnidirectional transducer in his original patent. Omni will give you a wider-sounding recording with more low end. Feel free to experiment with super or hypercardioid, too!"

There seems to be a few flavors of cardioid mics. The NTG3 is "Super Cardioid" but I am looking at the polar response diagram and it seems to fall into what is close to being used for the Mid mic. For that matter my Rode NT 3 may even be a better choice for Mid, since it is just "cardioid".

Your thoughts? As far as the Side mic, unfortunately I have nothing on hand that as a figure eight pattern to test out.

But even with my first rather unscientific experiment, I do like this a lot. Any recommendations on something that is reasonably priced but pretty decent for a side mic?

Happy Thanksgiving.

Jonathan

Yes the NTG3 is a hyper cardioid but it also has a phase cancellation tube in front of the capsule and as M/S basically works on phase principles that may cause all sorts of problems.

The S figure of eight will need to be back before the phase cancellation tube and not ideal for a coherant stereo image.

It would be better to have a cardioid or hyper capsule mic without a phase cancellation tube in front of it but also an omni mic could be used in place of the fig of eight one.

I have also got great results with a takstar CM60 and CM61 combination but as said previously it is far easier to just go for the sony M/S mic that outputs A/B for recording.

It may also be worth experimenting with the AT875R as that has a different phase cancellation concept and may not be as bad as a traditional medium or longer shotgun.

Without something more like a cardioid "M" microphone and a REAL bi-direcitonal (figure-8) "S" microphone, you don't really have what anyone would call "M-S".

But if you have some combination of random directionality and phasing combination that amuses you, nobody can argue with that. However, it is not clear if there is any practical or useful application?

There is serious problems with using a cardioid mic, pointed house left, instead of a proper bi-directional mic, as your "side" channel. I will call this the "FS" or "fake side" mic.

The most obvious problem is that you have no mic pointed toward house right. So the instruments on the [house] right side (typically the lower strings and brass) will not have any mic that picks them up well. They will be 45º off axis of the "M" mic, and 90º off axis for your "FS" mic. So the mix will tend to discriminate against these instruments.

OTOH the instruments on the [house] left side (typically violins, harp, keyboard) are directly on axis of the "FS" mic, so the final mix will tend to favor those instruments.

Also, if you were to look at the polar response patterns of the mics you propose, you would find that things don't "add up" properly. Ideally with correct M and S mics, the sensitivity and response of the mics overlap in such a way that they produce fairly even coverage across the sound field. As the output of the M mic is dropping off (as the angle away from the centerline increases) the output from the S mic is increasing. The sum of the two should be fairly uniform. If you use a hypercardioid for the M mic, it will drop off much faster than a proper cardioid, resulting in very uneven coverage across the soundfield.

A lot of this could be better illustrated if we plotted some overlapping polar patterns, and actually added values from the graphs. Frankly, I am not going to take the time to do that. But if you don't believe all the above, feel free to do so yourself. (This stuff is intuitively obvious to me, but still ... a picture and math are worth a thousand words.)

As Mr. Crowley indicates, if you find the result interesting, that's your choice. It will certainly result in two channels which are different, so in some sense of the word it will be "stereo." But don't think for a minute that it will produce uniform or correct M/S pickup.