Topic: M/S audience with SBD feed matrix

[kuba e]

DSatz, thank you a lot for nice explanation and for your time to write it. It is useful for me and probably for others tapers like me. I see that acoustic knowledge is very important for recording. This is the inspiration to read more about it in the books.

The only other thing that I maybe wish I had included would be, how this all interacts with microphone characteristics.

I guess roughly what kind of connection it has with microphone characteristics. Please, correct me if I wrote something wrong or inaccurately. The directional pattern influences ratio of direct and indirect sound that is recorded. Omni pattern has the sensitivity approximately the same for all angles and directional patterns have lower sensitivity for off-axis directions. And if we record in mono with one microphone and we would like to have a certain ratio of direct and indirect sound, omni must be placed closer to the source compared with directional patterns. I suppose it's more complicated in stereo recording, because the directional microphones does not point straight to the source, but the principle is the same.

The second characteristic that occurred to me is high frequency responses. If we record back in the room where the reflected sound prevails, it is better to use mics with good high frequency characteristics or to eq recording for heights in post. If I understand it correctly  - On the spot during a concert, our brain favors direct sound at the expense of the reflected. But when we listen to stereo microphone recording in our stereo, this benefit is partly lost and we perceive more reflected sound where high frequencies are missing. So when we record from the back of the room, we should be more observant whether there is need to emphasize the heights.

[Gutbucket]

All you young whippersnappers _{(get off my lawn!)} who grew up in the years since stereo became ubiquitous--you have it easy but you may not realize it. You can accept far larger amounts of reflected (room) sound relative to direct sound in your recordings than engineers could in the mono era. Stereo lets the listener's ears and brain sort things out somehow, even in some cases when there's more reflected sound than direct sound.

Put another way, in reverberant spaces, acceptable stereo recordings can be made at greater miking distances than good mono recordings can be. Your brain can't localize anything in a mono recording, so it doesn't take very much ambience to make a mono recording sound muddy; the direct/reflected sound balance is more critical. You also have to pay more attention to the character of the reverberation that you do pick up. Whatever room sound you record in mono had better complement the direct sound or else it can detract, perhaps severely so.

Again, listening for those things is part of the skill set that engineers had to have in the pre-stereo era. Stereo lets you get away with not listening as closely; there's more room for a mediocre sound balance when localization is there for the listener's brain to fall back on.

I've written about this at TS in the past, upon realization that the listening advantages and shift in recording approach of moving from mono to 2-channel stereo is further extended by the shift from two-channel to multichannel surround recording and reproduction, and how its value is more strongly apparent for ambient perspective live music recording than for other types of recording.  Done correctly, surround playback provides sufficient additional cues which allow our specially evolved hearing to more easily separate foreground from background, allowing the ability to "hear around" and "mentally separate and ignore" reverberance and audience chatter from targets of interest which then become more clear and distinct in the "mind's ear" of the listener, making it considerably easier to steer one's attention between particular aspects of interest in the recording. I find that for live-music taping where tapers don't have very much control over recording position placement and program balance, that becomes especially valuable.

With respect to audience-perspective live music recording, that "freedom of listening" naturalness represents the greatest value of surround recording and playback for me.  I feel it actually makes creating acceptable audience perspective recording in a highly ambient situation easier, in the same sense that DSatz describes making a decent 2-channel stereo recording is easier than making a good mono recording.   It takes more gear to do, yet the translation by the listener becomes easier.  If that makes sense, it probably represents the best argument I can make to other tapers for why I pursue surround recording, even though it's not likely to make my posting about it at TS seem any less obtuse or ridiculous to the majority of you folks!  Deep thanks to fellow TS members for your tolerance of all my postings over the years on this kind of arcane stuff few are likely to care about!

Long live stereo.

[Gutbucket]

But when you record in M/S, you really have one foot in the mono era, or maybe even both feet. The "S" microphone has to be placed with the "M" microphone and pick up its own mix of direct and ambient sound. But again that mixture is critical, and it MUST include a substantial helping of direct sound--otherwise the matrixing function (M + S = L, M - S = R) can't possibly produce consistent directional cues for the direct sound. If your mikes are so far back in the room that the "S" mike is overwhelmed with reverberant sound, then the M/S technique is just churning out fake stereo from ambience information.

By the way, since all X/Y methods (including Blumlein!) are equivalent restatements of M/S and vice versa, the same criteria hold true for them.

--best regards

Mono implies a depth dimension via how dry or reverberant a particular sound is with respect to others within the recording.  That depth dimension becomes more clearly discernible in 2-channel stereo, along with the obvious left/right directional differentiation ability which 2-channel stereo provides. The diffuse/pin-point differentiation aspect of 2-channel stereo is just as real and useful as the more obvious left/right differentiation aspects.  I consider it a more basic and more important aspect than left-rightness. 

Likewise, 2-channel stereo is able to imply an immersive environment beyond the left/right playback stage window between the two speakers, which similarly becomes more clearly discernible and mentally-separable in surround.  We can and do work that to our advantage when recording in stereo, and it is arguably more important to do so than for surround (where it becomes easier) just like getting clarity and depth perception correct in a mono recording without everything getting muddied together is more difficult and more perceptually important for good listening results, than it is with stereo.

Even if not ever recording in surround, one can consider these concepts and and apply the ideas in order to make better 2-channel stereo.  How can we make it easier for our highly-evolved ear-brains to parse the direct sound elements from the reverberance and audience reaction elements?  Record in such a way that the reverberance and audience reaction components of the recording are picked up so as to have greater decorrelation between channels, while the primary musical elements from the PA and stage sources are picked up with stronger correlation between channels.  The primary musical elements can then be reproduced with clear left/right imaging stereo cues, while the ambient reverberance and audience are reproduced with more diffuse and cloud-like stereophonic qualities.  In that way those different elements sort of remain out of each other's way so as to allow us an increased ability to focus on each part distinctly.

Well decorrelated ambience and audience is not left/right pin-point type of stereo, yet is certainly "real" in a natural hearing sense and not "pseudo stereo".  It is a different type of stereo, and the two work together to paint a more convincing picture.  Recording in ways such that much of the ambient reverberence and audience reaction is sufficiently decorrelated between channels makes it easier to differentiate sounds arriving from the band in front, reproduced so as to appear within the imaginary window framing the performance within the space between the speakers, from the sounds arriving from all other directions.  It's not doing so by actively reproducing the sound outside that stereo window in a discrete way like multichannel surround playback does, yet still conveys it in a way that allows our hearing mechanism to differentiate it more clearly.