What's so good about M/S?

[Virtual Aaron]

I often here about people banging on about M/S for stereo recording, why?
To me its always sounds unrealistic, distracting and (of course) it sounds compleatly different in mono, which to me is unacceptable.

In what situation is it superior to Blumlein, which always seems to sound fantastic.

I understand that M/S lets you adjust the width in the mix but you can easily throw up a third mic with a Blumlein pair.

Am I missing something?

What's the big deal?

[chris p]

Well, my friend, you have already noted the benefits: variable width stereo field with just 2 mikes (and remember thats VERY useful where you have just two tracks to record to), and phase consistent summing to mono (if fact, the mono signal is just the centre mic, which should therefore be omni if possible rather than cardioid).

There's no particular big deal. Like all such things, its just a technique that works with some things but not so well for others.

[Jason Dirckze]

You should try and track down Greg Simmons of Audio Technology fame and listen to some of his M/S recordings from the Himalyas. They are absolutely splendid examples of how beautiful M/S can sound when done with some great mics (Schoeps) and a great recording medium (Nagra V)

I think they were available as MP3 downloads from the Audio Technology website at some point

With the direct to stereo crowd, each has his own favorites and you'll have a hard time convincing them otherwise. I've been playing with ORTF lately (NT5's and an Mbox), with some OK results...

[Linear]

I often here about people banging on about M/S for stereo recording, why?
To me its always sounds unrealistic, distracting and (of course) it sounds compleatly different in mono, which to me is unacceptable.

In what situation is it superior to Blumlein, which always seems to sound fantastic.

I understand that M/S lets you adjust the width in the mix but you can easily throw up a third mic with a Blumlein pair.

Am I missing something?

What's the big deal?

I like MS for a number of reasons.

1) It only uses 2 tracks
2) The width can be easily adjusted at a later date
3) It has perfect mono compatibility (ie you can mono the stereo mix and the sides cancel each other out, leaving just the centre)
4) It's more a point source so there's less issue with phasing

You'd understand (4) if you've ever had a spaced stereo pair and the instrument moving around in between. trouble from the get-go.

I'm not sure why you think it sounds unrealistic, to me it's almost the perfect stereo image. Are you sure you're decoding it correctly?

I've seen some people do MS with the mics on top of each other. This is OK but usually means an elaborate mic stand setup. I find it easier to use the one stand with two boom arms, having one mic in front and the fig8 mic behind it.

One thing to keep in mind is that you don't dial in too much 'side'. That can sometimes make it sound funny depending on where the mic was in the room.

[Linear]

Well, my friend, you have already noted the benefits: variable width stereo field with just 2 mikes (and remember thats VERY useful where you have just two tracks to record to), and phase consistent summing to mono (if fact, the mono signal is just the centre mic, which should therefore be omni if possible rather than cardioid).

There's no particular big deal. Like all such things, its just a technique that works with some things but not so well for others.

I'm not so sure that I'd use an omni for the 'mid'mic. A cardioid would be much more appropriate, as you'd really prefer to reject the 'side' sound from the 'mid' mic.

[chris p]

Hi Linear Chris

I suppose its a question of what you want if its summed to mono - a cardioid or an omni sound. Horses for courses, I suppose, but you are right that there's more spill issues if using an omni.

[Chris H]

The 'sounding completley different in mono' issue is one i encounter when i position the mics and monitor in M/S without first getting the best spot and mic choice for the centre mic, so start with getting the best sound you can with the centre mic and only when happy with that, pull up the fig 8. From your description of how it sounds i'm wondering if you are doing something wrong, so it might help if you describe your set up. Also you dont allways have to use a matched pair. I often find that the mic i.m using for the fig 8, normaly a Rode K2 doesn't sound as good as the centre mic as a small diapram mic like an AKG 451 or a Neumann KM85

[mal stanley]

MS has its inherent weaknesses though can be particularly useful
in film/tv production where mono compatability is paramount..

In music if you have a mono cardiod and a figure 8, if in stereo
your figure 8 signal disappears (as it should), then you better be sure that
your cardioid has what you want....

In contemporary production it can have some use if for instance recording backing vocals or a choir so you can manipulate the width later...

But in general it's always worth checking your mixes in mono for any phase issues with mics...

But generally speaking I reckon MS not worth the trouble...

[Virtual Aaron]

OK, for the record, M/S technique is a combination of usually a cardioid mic as centre mic and is panned dead centre, and a fig 8 mic panned hard Left, and also hard Right but phase reversed.

I can't understand why this could be considered a perfect stereo image when there is no Left/Right imaging. IE: a performer can't move from one side to the other and expect that to correspond with left and right speakers, and as a result, your left and right ears, which is what would happen if you stood where the mics are. That's why I said it's unrealistic.
As for distracting, when you have something 180 degrees out of phase coming from two speakers, whenever you move your head, even slightly, it's sounds different and makes a whooshing sound, which doesn't help with trying to create the illusion that your there in the room.
The whole mono compatible thing, how can something be considered mono compatible if half your sound disappears? To me, it's mono compatible if it sounds the same or similar in mono. If I use M/S as a drum room setup (which I have seen suggested) and end up using a very roomy drum sound in the mix, the band is going to get an awful shock when they watch it on Rage on their old mono telly and the drums have disappeared!

I understand M/S might sound incredible with headphones, and it may have use in film (for which it was invented), or if you only have two channels available, so I guess I should clarify, I am talking about it being used in making a releasable record, that may be played anywhere, film, radio, headphones, shopping centres etc, and the number of channels you use just isn't an issue. But most suggestions I've read have been for this use, on pianos, soloists, group harmonies etc.

:end rant:

:)

[Chris H]

No whooshing sound with my m/s and if someone walks across the m/s miced stage, thats how it sounds...just like someone walking left to right or whatever. You know you only reverse phase one side of the fig 8. ie you record it on one track and in the mixer pan it left than take a post fade direct out , put it in a separate channel on the mixer , bring the fader to unity , rev the phase and pan right. then the fader of the original chanel of the fig 8 can determine the ammount of side, or stsreo wjdth.

[ZiggY!!]

If you record a drumkit via M/S and switch is to mono the kit should definately not disappear. If it does you are doing something terribly wrong. The side channels will disappear but the middle shouldn't, and it doesnt get much more mono than that. Its just like sticking an SM57 in the room pointing at the drum kit.

[Virtual Aaron]

Chris H, how can you get the sound to shift from left to right when the Left/Right mic is the same single fig 8 mic?

Ziggy, if you use more sides than mid then your drums are going to get a lot quieter.

Mono compatibility to me is when signals add together in-phase, not cancel out and disappear. If I put my whole mix out of phase it will sound nice and wide, but I wouldn't consider it Mono compatible because it will be completely silent in Mono.

Anyway, I'm not bagging out the technique, I'm just wondering about it's usefulness in record production. I've used it many times in various applications to try to work it out, but have always been underwhelmed by it's performance. It just ain't for me I guess.

[Linear]

Chris H, how can you get the sound to shift from left to right when the Left/Right mic is the same single fig 8 mic?

Ziggy, if you use more sides than mid then your drums are going to get a lot quieter.

Mono compatibility to me is when signals add together in-phase, not cancel out and disappear. If I put my whole mix out of phase it will sound nice and wide, but I wouldn't consider it Mono compatible because it will be completely silent in Mono.

Anyway, I'm not bagging out the technique, I'm just wondering about it's usefulness in record production. I've used it many times in various applications to try to work it out, but have always been underwhelmed by it's performance. It just ain't for me I guess.

Hi Aaron,

Don't take this the wrong way but I think there's a couple of bits missing in your understanding of MS.

Without getting too geeky, you need to think about the physics of what is happening.

Once it is decoded, you get

L = M + S
R = M - S

Thus add L + R = M

There are no phasing issues at all because the two capsules are (in theory) at the same point.

The trick is to visualise what is going on. It took me a while to 'get it'.

Sound coming from the front is effectively nulled from the side mics because the front and back is 180 degrees out of phase and the phase has been flipped for decoding. Not to mention the fact that a fig8 mic does a great job of rejecting sound off-axis.

Sounds coming from either left or right are mixed with the M mic and effectively nulled off-axis. In other words, a sound coming from hard left would reach the front of the side mic out of phase to the rear and Mid mic. The mid and rear mics would cancel each other out (to a degree) leaving only the L signal.

This is why you get such a good stereo sound field, with adjustable width.

I think what you need to do is set up a MS mic arrangement, record it whilst making noises around the mics and see for yourself. It really works, and works well.

I did an MS recording at (the now closed) Side On Cafe. The MS mics were a pair of 414's, set up in the middle of the room amongst the audience. The sense of depth and realism is what got me hooked on MS recording.

Chris

[Virtual Aaron]

Hey Chris,
You've just made me realise what (I think) my problem with this technique is.

My understanding of how M/S decodes is correct but it just occurred to me that the two mics I have usually used have been older vintage mics that, on their own, actually sound quite different, which is a major problem, because it is of paramount importance that the S mic cancels out the M mic with some of it's information, which is not happening very well with these mics because they actual sound quite different.

The key to this technique is the fact that when sound hits one side of a Fig 8, its phase is reverse to what it would be at the same point on the opposite side. So when you flip the phase and pan them, one side will add to the M mic and the other will subtract.

I reckon mine ain't adding and subtracting properly and it just sounds weird.

I will try yet again when I can with matched pairs and hopefully I will solve this enigma.

[Chris H]

Check this link out for detailed info....it's not that the fig 8 cancelles the centre but adds the sound as it moves the diaphram of the fig 8 ie left immage as the side reflections (reather than the direct soundfrom front) move the left side of the fig8 mic being the + of the electric current ant the right immage being the side reflections hitting the right side of the mic.
A picture sais a thousand words.

http://www.uaudio.com/webzine/2005/december/index4.html

[tall_phill]

The New Stereo Soundbook has an exceptionally through description of the functioning of conincident mic techniques including MS. I would highly recomend reading it.

http://www.wesdooley.com/aea/The_New_St ... dbook.html

It also has handy information w/r/t MS such as the different (ideal) patterns created when used with Mid mics of different polar patterns, and different ratios of mid to side volume levels.

Two other neat things about mid side recording and processing are:

The Centre of the stereo of image is immediately on axis of the mid mic, rather than off axis of both mics.

Independent processing of the mid and side channels (ie eq or dynamic) can lead to some very powerful ways to shape, and dynamically shape, the sound field.