MS recording & LtRt Dolby Matrix Issue???

[SlateSound]

Hello,

I'm looking for some info here.

Basically I'm looking to purchase a fairly high end MS setup for recording SFX exclusively, ambience etc.. Schoeps or Senn

During my research I have come across bits and pieces about MS recordings being a problem when creating an LtRt from a 5.1-7.1 mix.

So does anyone know about this issue here? I've read that it only becomes an problem if you mix the sides in too much, but what is too much? no one has explained the theory or math behind the problem so I don't really understand it except that the fig 8 S+ and S- are 180 degrees out of phase which each other and because the dolby matrix is flipping phase to get the 5.1 down to the LtRt it can throw the MS stuff into the rears.

Schoeps (Rob James) briefly mentions the problem in a review of their DMS plugin and states that it's not a problem anymore. Which is great but doesn't really make sense because the issue is caused by the sides being flipped which still has to happen when creating the L R from an MS recording..

Here's what he says

"From the location recordist’s point of view, MS mics are very useful since they enable recordings to be made using the same techniques as mono. I write from the perspective of a re-recording mixer with extensive experience of being on the receiving
end of stereo MS recordings. I have observed that many of the mic combinations used result in ‘phasey’ recordings that are very uncomfortable to listen to. This is equally applicable to ‘all-in-one’ designs and to separate capsules. Still worse, such recordings played havoc with the matrix used in Dolby stereo. This led to blanket advice from re-recording mixers not to use MS for film. However, in reality there are some honourable
exceptions and one of the more notable has always been Schoeps."

Not sure what he means by this.

If anyone can shed light on the subject I'd really appreciate it.

Thanks

John

[Newpostguy]

Not your answer but I find that you get better (less phasy) with two seperate mics for ms than a fancy all in one ms package

[MIKEROPHONICS]

Coincident mica should be by default less phasey than spaced mics since the time of arrival difference is more in a spaced configUration, and surely phase is to all to do with timing difference?
MS stereo recording has the greatest mono conpatability compared to spaced techniques.

However I feel this is semantics.

AB/MS is however totally interchangeable as long as you set up your channels correctly. When using MS (i.e when recieving stereo sitcom split booms) one would have M and S faders for each boom, and you are converting your ms into AB or left right stereo for mOnitoring and adding to the mix bus. Only a fool would have the S larger than the M unless it was for an extreme L or R piece of dialogue. This would of course be analogous to bad boom operating as the more logical option would be to have more of the dialogue on the M central cardiod axis and in the mix, loose the S and pan the M.

Too much width of anything will of course go to the rears in a matrix set up



MS or AB who cares, a savvy dubbing mixer isn't phased (bad pun). - good recording or bad recording - now you ignite my passion!

Sometimes SFX have a greater width component than centre component. Do you care if the recordist used AB or MS? No if given in AB then you would wind the pan pots in - or in MS you would drop the S fader down.

[mr.armadillo]

Originally Posted by MIKEROPHONICS

AB/MS is however totally interchangeable as long as you set up your channels correctly.

This is misleading since MS and AB describe recording techniques. You can't decode MS to AB or vice versa.

Originally Posted by MIKEROPHONICS

No if given in AB then you would wind the pan pots in - or in MS you would drop the S fader down.

Again, totally different effect. Winding the pan pots in on a AB recording is totally against the principles of time-of-arrival stereophony and will ultimately result in phase issues, while dropping the S fader won't.

[Postman]

I think you're both right. Since this thread is about matrix problems...

From a mixing perspective, when there are matrix steering problems and material is being unintentionally pulled into the surrounds, the fix for non-MS material is to narrow the panpots. This lowers the level of much of the out-of-phase material. Does it cause phasing? For an XY or AB pair, sure it does. But consider that in ANY matrix system, there is ALWAYS some phasing due to mono combine because the center speaker is always derived from a mono combine of L & R.

MS recording has its own drawbacks. While it provides the allure of a "perfect mono", that perfect mono is from a cardiod microphone, not an omni. That type of directionality may not be at all desirable, especially for large musical groups or wide sound field.

Personally, I don't care as long as the captured recording is a good one.

[MIKEROPHONICS]

I think POstman is right in that we are both correct -but that was my point too!



I agree that MS recording is different to AB recording techniques - and each has its pros and cons

AB stereo is often converted to MS - how about mastering, where different properties could be applied to S instead of M (such as over bassy reverb bloom?)

MS has great uses in post and was originally used as the easy way to video edit stereo in Beta SP days (and 1" - yes I remember lining those puppies up!) where the video chaps would listen to the M and cut the S along with it (but not monitor the decode).

AB and MS are two mathematical are to describe the same relationship and are TOTALY interchangeable

Ten ways to skin a cat........(no cats were harmed in the making of this post)

cheers

[TimNielsen]

I won't argue the math involved here, but as someone who has been recording, editing and designing FX for film for about a decade, and using MS as my main recording technique, I'll offer some thoughts.

First, the biggest thing to realize with MS is that using a cardiod mic, the widest angle of stereo you can expect to get 'usable' is about 90 degrees, which would be achieved with a one to one ratio of mid mic to side mic. Reducing the side mic will narrow the image, all the way to mono if you pull the side mic out completely. What you don't want to do is to increase the side mic above the mid mic, and from my experience, phasing or other MS issues really only apply when people do this.

What you're 'hear' will sound to many people 'wider', but it's also phasey and I would bet that many issues with LtRts arrive from that. But phase issues in an LtRt can derive from material recorded in any format, and I'd expect you'd have more issues with things recorded with spaced omnis, which might be preserved fine in a 5.1/7.1 but when getting matrixed summed and, have a chance of phasing.

I love MS for many reasons, first and foremost, that in a single zeppelin I can record a true mono signal, and a great stereo image as well, and choose which I want later in post. It's convenient, and when done right, sounds great. I have both a Schoeps MS rig (CMC6 XT with MK41 and MK6 in figure 8 mode) and also a Sennheiser MS rig (MKH30/50 combo). I tend to prefer a hypercariod in the center position, mainly because I prefer a hypercardiod as my mono FX mic.

But you can also swap out an omni for the center mic, MS works perfectly fine that way too, and you end up with a 180 degree field of view.

But I've been through many film mixes, and many LtRts, using thousands of my sounds getting collapsed down, and it's never really been an issue.

[SlateSound]

Hi Tim,

Thanks for your input.

I was curious about which set up you feel is quieter the senns or schoeps?
What recorder you prefer?
Have you ever recorded Double MS?

Hmmm, I'm hijacking my own thread.. if you've got the time maybe you can reply in a PM or email?

Thanks

John

[email protected]

[Ray JB]

I agree with Tim, MS is certainly THE way to record stereo. People used to be paranoid about using MS derived recordings in conjunction with any phase-related surround processes (Dolby Surround etc) but as long as you are not too wild with your Side signals you'll be fine. I use the Sennheiser combos of either MKH60 and MKH 30 in a Rycote MS stereo windshield (if I am after a fairly front-focussed sound ie: bird recordings etc) or MKH 40 and MKH30 in a somewhat smaller MS Rycote which I like for a wider feel for atmospheres. I keep MS signals discrete in my recorder and only monitor in stereo, until I get a chance to process the recordings back in my room. I then end up with 3 perspectives, Mono, Stereo and of course my Side signals which can often end up being used for an odd perspective (ie: widely mice'd audio - useful for an "off mic" type of feel if needed.

I've found that the MS stereo decoded to AB stereo collapses very nicely when mono'ed.

I too am interested in double MS as per the Schoeps techniques but have not tried that yet.

The Sennheisers are super quiet. The combo of Sound Devices 7 series preamps and Sennheisers are pretty strong. I would move over to the newer Sennheiser 8000 series if they brought out a figure 8 capsule, but alas it's not here yet.

[matt-o-]

Hmm, I do not want to appear educational, but I had learned the terminology in the way, that XY describes a coincident level-based stereotechnique and AB a time-based one. Therefore the coincident level based MS technique could only be related to XY techniques but not to AB ones. It might be irritating to mixup XY with AB.

Another comment/question, although a little bit off-topic, I really have problems translating MS to 5.1 properly. With ambiences and SFX there are several techniques, which work, but especially dialogue related elements, as for example, documentary production sound, which is very often recorded in MS, is difficult in that regard.
As there is no 2-ch stereo in filmsound, how do you derive the center channel? If you use M for the center channel, you have to pan -s and s to left and right, which means, that the MS decoding is done during the playback in the cinema, and you have to completely trust the playbackchain there (which in my experience is a no-no).
Any conversions to XY and appropriate panning to half left and right would make the dialogue mushy, because you would playback from phantom in-between positions and not from precise discreet ones. Sometimes I simply pull the pans a little bit in, to reduce stereowidth, but my basic translation problem remains. Any insights?

greetings,
matthias