M/S Matrixing and Input linking???

[Jonathan Levin]

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."

[Richard Crowley]

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.

[Jonathan Levin]

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

[Greg Miller]

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

[Jonathan Levin]

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

[Richard Crowley]

Originally Posted by Jonathan Levin

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.

[Jonathan Levin]

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

[Richard Crowley]

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.

[Gary Nattrass]

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

[Jonathan Levin]

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

Mid-Side Microphone Technique - YouTube

[Greg Miller]

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.

[Gary Nattrass]

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/161...Ecm-Ms957.html

[Jim Andrada]

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.

[Jonathan Levin]

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

[Richard Crowley]

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".