Stereo Miking Techniques (M/S help please!)
 

Thanks to a previous thread I got my feet on the ground and have been doing searches and reading up as much as possible.

I know I want the Oktava, and the rest I am unsure about as of yet (this is where your help comes in!)

I see that M/S seems to be a popular stereo technique, and I THINK I understand it...the versitility of being able to alter the stereo spread seems appealing...EXCEPT for that darn side mic!

A figure of eight microphone?! I have searched and searched...and about two or three have come up. It seems to me that either this set up is WAY out of my price range, or the side mic has some other name

Okay, so here are my questions:
- Are figure of eight microphones called anything else? How much do they cost
- Is the figure of eight mono sound? If so, how does this part work...if the mic is picking up both L and R...how! The hookup?
- Is it possible to use a regular stereo mic AS a side mic in the M/S set up? Pros/Cons?

Okay, I think that's it for now
Thanks for your time!
Rob

Rob
It's no mistake, the figure 8 is expensive. I can't remember if I gave you this link. Don't listen to everything people tell you (including me)

http://www.oade.com/Tapers_Section/faq-mic.html

yep, I read up on that...the other one I looked at was X-Y but...I don't know...it just doesn't seem to be (in theory) what I want.

It sounds good for getting a wide pattern...but what I liked about the m/s was that you could keep 1 hypercardoid directly positioned at the main sound source. This way I have a mono track of specific voice/whatever else I would like to focus on and then a mix of background with the side channel...and I can fidget around with the differences.

If you had any insight on the last 2 Q's that'd be really great (or anyone else!!!)


Thanks again,
Rob

This mic does M/S stereo...
 

http://www.audio-technica.com/prodpr...ST_english.pdf

It says it has a line-cardioid and a figure-of-eight element and that it is capable of M/S stereo. It will probably cost you $700...

I haven't used that microphone and I am absolutely no expert in the field (just learned about M/S stereo yesterday).

If you want a poor man's way of doing M/S matrices, you can always build an out of phase cable. It accomplishes the same goal. Just be sure your two identical mics are as close together as possible when recording, so that the sound wave cycle is the same when it hits both mics.
I'm surprised more Euro folk haven't chimed in here. BBC has been using this technique for decades.

Douglas, could you explain a bit more or hit me with a link? I'd like to read up on this one too.

thanks,
Rob

Most microphones that offer a figure 8 pattern are expensive large capsules
like the Neumann U89 or the AKG 414. I think Beyer used to make a
kick drum mic (dynamic) that looked a bit like the old 'Elvis' style Shure 55.
The Beyer offers a figure 8 pattern
that worked well when mic'ing congas (it looks to the sides), BUT
was very 'tubby' sounding (which is okay for somethings).

If you really want good M/S results in a single unit shotgun
check out the Sennheiser MKH-418.
And of course there's always the Schoeps $4500 kit of MK41 and M8
with the suspension system, cable, preamp, blimp and deadcat.

www.posthorn.com

You can build a cable that has reversed polarity on pins 2/3, and then plug that into your mic input/cam input.
You can also find small mixers with phase reverse that accomplishes the same task.
If the two mics are placed VERY close together, as close as physically possible, the same sound wave/pattern hits the elements of the mic at the same time. With one mic pointed at source, and the other mic at a 45degree angle from source, with one 180 degrees out of phase, you have the same thing as an M/S system.
A quick search on Google for M/S mic, phase turned up a buncha responses. what looks like a good one is
http://www.radiocollege.org/readingroom/articles/sm/mic_techniques.html

<<<You can build a cable that has reversed polarity on pins 2/3, and then plug that into your mic input/cam input.>>>

Hold on here. M/S takes three channels in *order to keep control*
of the amount of ambient sound in the stereo mix.
So, how do you make it work with only two channels? You plug in the first mic (let's use the hypercardioid)
into channel 1. The 2nd mic, which traditionally a figure 8 patterned capsule
is sent to channel 2.

Later in post you *pan channel 1 to the center of the stereo mix*
and then *take channel 2 (fig 8) and duplicate/split it*. The original CH2 you
hard pan left and the duplicate you phase reverse and hard pan right.

The amount of ambience is then determined by the amount of
channel two and its phase revsersed twin's levels in the mix.

Hit the mono button and the two "ambience twins" cancel each other out and
leaving the hypercardioid's signal (mostly) all by itself.

The out of phase cable goes on one mic only, with the other end of the out of phase going to 2 mic channels. The signal is out of phase from the other mic. The two are combined either in mix or post stage, they can be muxed at any point. I've got one, as I say, I learned it many years ago from a guy at BBC when we did a project together. Just doing a quick search of google, I found lots of references to it, cuz I'm too lazy to type much.

http://homerecording.about.com/library/weekly/aa112899a.htm

http://www.turneraudio.com/tech/stereomic.html

http://www.modernrecording.com/articles/soundav/link2.html (wiring diagram here)

http://www.transom.org/tools/recording_interviewing/200106.stereomicrophones.jtowne.html

M/S is ideal for video because it is 100% mono compatible, whereas other stereo techniques can cause distortion effects when mixed down to mono.

Unfortunately I don't think you can buy a cheap figure of 8 mic.
You're talking of over $1,000 for a Sennheiser MKH30 or a Schoeps CMC6/MK8. You would then want an equally good mic for the Mid channel, e.g Sennheiser MKH50 or Schoeps MK41, which would be another $1,000+.

I would doubt that it is worth it unless you're recording classical music. Also the quality of the mics is wasted if you are recording direct to DV camera. You would need to record dual system, with a top quality AD converter. Top quality mics are quite cheap to hire though.

The Sennheiser MKH418S is a very good shotgun (MKH416) with a relatively cheap figure of 8 mic built in, just to give stereo ambience, but it is over $1,000.

Why not just spend a few hundred dollars on a pair of matched Oktavas and try out X/Y stereo and spaced stereo arrangements?

Patrick

Doug, I read every one of those, and if you truly can do m/s with 2 hypercardoids, I definately missed it...I read as best I could.

What if you use a oktava and one of those cheaper T bar shaped stereo mic's? Would that work okay for m/s?

As it stands I guess I am going to be getting 2 oktava's for X/Y

Also, avr.ca hasn't responded and the best deals for oktavas all use cardoids, would using a cardoid setup be that much worse? (using both indoor and outdoor)

thanks everyone!
Rob

wait...maybe I do understand...

From: http://www.transom.org/tools/recording_interviewing/200106.stereomicrophones.jtowne.html
I still can't fully wrap my head around how this is stereo though...if there is a car racing by from left to right...and you are recoding a mid and, say 45 degree angled side mic to the left, how do you get a right channel that actually is right? Maybe it does work...sorta fake like...It seems like the answer is on the tip of my tongue...or brain i suppose.

Now, if I am purchasing the Rolls MX4s Mixer...I would pan the mid oktava to the left channel, and then the side oktava to the right, and then some how mix it up in post?

How DO you mix M/S in post?

Thanks again, and if I am totally wrong on some (or all) things, feel free to tear me apart!
Rob

If you read the http://www.transom.org/tools/recording_interviewing/200106.stereomicrophones.jtowne.html page, and look at the
http://www.transom.org/tools/images/msmatrix.gif image

You can see how the split cable makes up for the figure of 8 mic. It's 2 signals from the same mic, one in and one out of phase, matrixed at the mix console or in post.

"Also, avr.ca hasn't responded " Jason was out sick, try calling.

<<<I still can't fully wrap my head around how this is stereo though>>>

It's NOT stereo, but a 'faux' stereo. You are "wrapping"
the center hypercardioid signal with ambience.

<<How DO you mix M/S in post?>>

Read my previous post ;)

PS I have NEVER known an audio engineer (that had it together) to
use ANYTHING but a hypercardioid mic and another mic with
a figure 8 pattern for M/S. Usually the same kind of mic, like a AKG414
that has switchable patterns.

Experiments are always welcome.

Bryan, I emailed them really late in the night...probably about 4am or so, I have no time during my day. Either sleep, work or squeeze this in for a few mins late at night or right before class.

I guess what i'll do is get the two oktavas and test both X/Y and faux m/s

I know I keep asking...but are cardoid's really not comparable to having hypers? A few sites recommend them with X/Y and a few with m/s...and if they are (as it stands right now) the cheapest form, am I shooting myself in the foot if I go ahead with the cardoids?

Thanks Jacques, Bryan, Douglas, Patrick, and Ralf
Rob

First of all, there are plenty of mult-pattern mics with figure 8 for dirt cheap. Hooray for Chinese sweatshops! ;\ Here's one for $150, and I think there are cheaper ones, too. http://www.musiciansfriend.com/srs7/sid=040218110858066208214068921825/g=rec/search/detail/base_pid/270491/

Secondly, I wouldn't use M/S while shooting a film. You have to decode it in post to get the stereo sound. Plus, the setup is bulky. Too much of a pain in the a--, and too many places for something to go horribly wrong. To be honest, I wouldn't use stereo at all, since you can always pan stuff later on in post. I guess I'm just not clear on why you think you need to shoot in stereo.

As far as the hyper vs. cardiod, there's not a massively huge difference, but it's still worth having the hyper. For another $64, why not just buy one? The great thing about the Oktava is that if you don't like the way one capsule is sounding in any given situation, you just unscrew it and try another one. Hell, I'd get the omni capsule, too, in case you just want to stick the mic in a plant and record a round-table discussion or something.

Good luck,
Ryan

"It's NOT stereo, but a 'faux' stereo. You are "wrapping"
the center hypercardioid signal with ambience."

In a way, all stereo techniques are "faux". The only genuine "stereo" is to record with a dummy head, and listen with headphones.

M/S is no more "faux" than XY. In fact, for any given M/S arrangment, you can produce an identical stereo field using an XY pair. For the maths behind this see

http://www.wesdooley.com/pdf/technique.pdf

Using my NLE (Vegas) it is very easy to do the stereo matrix in post production. Copy the mid channel to one audio track. Copy the side channel to another 2 audio tracks. Invert the phase of one of these tracks. Play all 3 tracks together.

The only practical problem is actually monitoring the stereo sound live, while recording M/S, unless you have a matrix decoder. I use a Mackie mixer to do this, but it's a bit complicated, and needs a few jumper cables.

Patrick



http://www.wesdooley.com/pdf/technique.pdf

I've been looking at this, too, but I'm not sure if a true M/S arrangement is worth the trouble.

Meanwhile, I've taken to putting a Zoom H4 on the floor or gaffer-taped to the back of my camera, to capture a stereo ambience track. Mixes pretty well with the mono shotgun/lav dialog track.

Rob... not sure if you've found this link already, but it explains a great deal about understanding MS. mid-side (M-S) stereo recording technique

SOmetimes it is done with an omni in the middle. Some feel an Omni gives a truer sounding recording of say a piano for classical music.

I'm not a fan of M/S at all. Recording an orchestra in a concert hall, there's likely to be way to much out of phase component from the walls, resulting in a boomy final result when you try and raise a soloists level. In my experience, most musicians hate it.

Handing an M/S job in to the sound editors and mixers won't get you any thanks, they're all on tight schedules with no time for messing with it. And you have to send along comprehensive sound charts for every scene.

Try mixing M/S and XY SFX together in a show, IMO it can disorientate you and the listeners.

M/S only gives you 3 axis, left/centre/right .. at various levels. There's no sound at the 45 degree points.

M/S is a 1950s radio technique at the introduction of 'stereo' Its main attribute was, early producers could collapse it to mono by just using the centre mic for broadcast by stations with mono transmitters.

Cheers.

Jimmy

I did am M/S recording of a brass band concert Friday and I tried an omni in place of the cardioid or wide cardioid I usually use - I think it sounded pretty good - quite natural indeed. I'm thinking of doing our next concert with both an omni and a cardioid as well as the figure 8 and then I can compare them directly.

Allan

I'd have to say that I haven't noticed an issue with a hole at 45 degrees. All in all I've been quite happy with M/S.

By the way, any more on your coming back to Tucson for the aircraft renovation? Weather is starting to get quite nice as we enter Autumn - it was only 102F or so today!

Hi Jim, IMO M/S requires much experimenting to get a your result, you have more to consider and move about for the sweet spot, than with XY. Repeated recordings in a good hall with the same group would be necessary.

And I think you mainly balance it in post to fill in the 45d holes. I don't see any mainstream M/S classical releases these days.

The Convair has reached a good stage in rebuilding now, we should be along after Xmas. We're doing a DC4 to get it out of Brisbane first.

HARS

Cheers.

Give me a bit of notice before you show up and we can organize dinner and drinks.

I'll put a snippet of Friday's concert on my web site and post a link. The omni really sounded pretty good. Biggest problem we face is that we perform in some pretty poor halls.

Well, maybe that's the second biggest problem - biggest would be US!!!

Just a couple of links to a couple of pieces we recorded last week. Recording was M/S with Figure 8 and Omni

Nothing done in post, M/S -> Stereo in the mixer.

Performance could have been better (a lot better!) but for what it's worth.

(I'm "guilty" of the BBb Tuba part.)

www.j-e-andrada.com/Colonel_Bogey.mp3

www.j-e-andrada.com/Walk.mp3

I find m/s is a very useful technique to have available for certain things - but not all. For me, the disadvantage when recording on location is that monitoring is difficult - you can't hear what it really sounds like. Having the side mic on one ear and the mid on the other sounds very strange. I keep meaning to build a little matrix box, but never get around to it. If you are recording material with clearly defined and possible moving sound fields - think motocross, horse and motor racing - aircraft, that kind of thing, then using x/y or even a/b presents big level changes that go from very loud one channel, almost nothing in the other as gains are linked, then a fast channel swap as they pass the camera. This is very difficult to sort out in post, and frequently summing l and right produces a hole in the middle, it goes up, down, up down as the sources goes past. M/S works well in these examples, with a wide-ish cardioid, or an omni. A hyper-cardioid gets you a similar effect from further away.

The use of x/y pairs for recording orchestras and choirs is pretty common, but the angles need carefully adjusting to make sure the people centrally placed get included - but often, as you move the angle to get decent centre coverage, you start to lose the outer edges. Obviously moving the mics in or out can sort this one, but you also get the ratio of direct to reflected sound messed up. In a building like a stone built church or cathedral, the reverb can start to dominate, robbing the clarity. An m/s configured pair can be tweaked afterwards to give you the best results.

I've got a recording in the diary at a church - quite a large one with difficult acoustics. I'm going to record it with a variety of microphones at the same time, as an experiment. I'm planning x/y cardioid, a/b omnis and m/s - I'll then be able to produce different versions. That's at least the plan at the moment.

A couple of comments on selecting mics. If you have them, a couple of figure-8 microphones in an x/y pair work really well in a building with good acoustics. If you do use cardioid microphones, remember that if the ones you have are designed for multi-purpose use, then the design may well cope with close in speech or singing by rolling off the bass end, to try to prevent the boominess and bass extension cardioids have. Using them at a distance can often produce quite thin sounding recordings. Omnis tend to have a rounder sound.

To be honest, though, all these clever techniques require a sound op, because a good set of ears are required. They're not suitable for unattended automatic recording on a video camera. If you need to record quality sound on a video camera, then an dedicated stereo one piece mic is so much simpler, and less prone to messing up.

One of the best stereo mics I ever used I bought in 1996 or so. A Sony side-fire mic. Great sound. One small dial on the front with degrees indicated for how wide you wanted. I discovered later it was an m/s mic, hence the adjustment knob, but with a dedicated l/r output with de-matrixing inside. If they still made it, I'd buy another straight away.

I used to have similar little sony mic that was really quite inexpensive - also M/S with a little switch to select the angle.


My SD302 mixer has an M/S option which decodes the M/S into regular stereo so that is what you hear in the earphones

I use M/S all the time and it is an ideal technique for video and film work as the mic is single point.

it has to be said though that it is most useful as a matrix within the mic that then outputs an A/B signal. Many a sound recordist has tried to record M/S but because it works on phase differential between the cardioid and fig 8 mic you need absolute phase cohereance all the way through the process and this is hard to do with analogue devices and mixers.

You also run the danger of an editor just taking the M signal as this will be the loudest and it all ends up being mono.

As said an M/S matrix mic that then outputs to A/B (or left and right) is the ideal stereo mic for video and boom work as it will be single point and can be panned with the camera without any change in stereo imaging, try do this with an A/B mic and the stereo image will be all over the place once each shot is edited together.

I use the prosumer sony M/S mics and have done for sound FX on major drama productions over the years, the main dialogue is usually recorded on a sennheiser 416 here in the Uk so adding stereo fx from an M/S mic works really well in post.
I have also been lucky to use an AMS Neve digital console for most of my dubbing career and it actually has an M/S control on it for stereo A/B signals so that you can adjust the width of any stereo source in post.

As for mics I used to have an AMS Neve (calrec) soundfield mic that had four capsules matrixed into M/S http://www.soundfield.com/company/company.php

This was a seriously expensive mic in its day and you could also do quad matrixing from it, the BBC still use them in the Albert Hall and for FX on Wimbledon.
I personally used the ST250 and there are more details of the advanced matrixing here:http://www.nada.kth.se/kurser/kth/2D...NDED%20III.pdf

For the past 15 years I have mainly used two cheap sony prosumer mics the ECM-MS957:ECM-MS957 | One-Point Stereo Microphone | Sony | SonyStyle USA
And the ECM-MS907:ECM-MS907 | One-Point Stereo Microphone | Sony | SonyStyle USA
They can both be changed from 90 to 120 degrees angle and they both output A/B to my recorder either a minidisk or laterly a sony D50.

They are also cheap as chips so it can be a good way of trying out M/S mics without too much outlay. There are also more expensive M/S mics on the market and the single design route is far easier than trying to fit two different mics into a blimp.
Edirol also make a good M/S mic:Edirol CS50 Stereo Shotgun Mic - For Edirol R4 series
But for me I find the sony prosumer mic does the job.

I was reading along in Gary's post, ready to protest "but if you don't actually record your M/S signal, but decode it to L/R, you lose the ability to adjust apparent stereo width in post!", one of the really cool things about M/S technique.

Gary, are you saying here that this particular console can recode L/R back to M/S, adjust width, then matrix back to L/R? I think I've heard of this trick, but if anyone has further details on how to accomplish the de-matrix of L/R back to M/S I'd be very interested to learn more.

This is all assuming an original M/S source...

Seth,

Take a look at Waves SI - you can change the stereo spread of any A/B stereo track.

There's also a plug in from Brainwerks in Germany that does it (and is cheaper/no dongle)

I think that they effectively transform the A/B tracks into M/S then change the spread, then retransform

Yes guys the AMS Neve Logic and DFC digital consoles have two controls on stereo channels that can zoom the image from mono out to 180 degrees, they can also matrix M/S but as I mainly record A/B I just to us the width control to widen or make narrower the stereo image.

I am now on pro tools and I have a free plug in called bx-solo from brainworx that can do the same job on any stereo A/B signal:http://www.brainworx-music.de/index....6&um=2&lang=en

All stereo A/B signals follow the M/S principle of
M=Mono
Left= M-S
Right+ M+S

So if you increase the S content it will widen the stereo image and if you decrease the S signal to zero you will get mono.

The original Dolby pro logic also works on this principle where the signals are as follows:
Left=M-S
Centre=M
Right=M+S
Surround=S (two rear speakers in mono but with filtering applied)

Hope that all makes sense.

Actually M = Mid (*not* Mono)

MS = Mid and Sides

But you are correct in saying that L=M+S and R=M-S.

Going the other way:
M=L+R
S=L-R

Ah, John, thanks for going back to the math. Now I get it! I can set up a dematrix in my NLE next time I get a recording from an M/S mic that has an internal matrix to L/R.

OK - found the link to Brainworx Solo. I use Waves SI on my main system but I installed this on my notebook so I don't have to schlep the Waves Dongle around with me.

Take a look - nice plugin for the price (free!)

MS-Mastering Tools by Brainworx-Media

Personally I use the Voxengo (free) MS plug-in.

I've used both my own Rode NT4 X-Y mic and a 'loaned' Sanken CMS-10 phased array mic to record live music and drama events. The Sanken can also be switched into hypercardiod in which mode it is a very capable shotgun. It's an expensive beast, it is quite short as it was built to go on a camera although I've always used it on a stand.

Decoding M/S in post is pretty easy, took me less than 10 minutes to nut out how to build a M/S decoder in Vegas, no plugins required.

What has not been mentioned here at all is any stereo recording technique relies totally on microphone placement. As I've learnt the hard way this is critical. A few inches or a few degrees can make all the difference.