Stereo mics

Rick R said:
I had a few clients that wanted to see the VU meters hammering on the multi-track recorder, which was severally saturating the tape and it was bot pleasant sounding saturation, so on a break a re-calibrated the machine meters to read 6 dB higher than it actually was, it sounded good and the client was happy.
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;~) On another film where the director wanted to see the red LED's on the meters flash ALL the time one of the techs suggested feeding a DC offset in, though I don't think they actually did that. They did post a daily peak dB reading each day from a SPL meter they had set up. Nobody entered that stage unless they had to it was just insanely loud.
 
Throwback said:
Hi Bruce,

BBGs are not just fine for indoor work, but are useful outside too. Goodness, as per Rycote's own specs they offer 30dB of wind attenuation that rises to 50dB with the windjammer, and these figures are borne out by real use. They are good for stereo pair recordings of ambiences for that reason, not least lending themselves to spaced omnis. Of course, there are times when the greater wind protection of a full blimp (including those designed specifically for ORTF and MS, such as you link) is needed, but, all the same, BBGs are a useful part of the diverse arsenal of wind protection.

Cheers,

Roland
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The only reason to use coincident pairs and such is for mono compatibility, unless you just like the sound. If mono compatibility is an issue then it's important but for film post it is as a rule not an issue at all. If an editor wants a stereo sound to be mono standard practice (in the US anyway) is to just use one of the tracks and toss the other. Unless you are planning on releasing on 16mm your final format is going to be stereo or larger.
There was a lot of discussion over the years on various options for SFX recording in stereo. Some love M/S, some are big on XY and some insist on tual mics. The switchability of some mics sounds like a great idea but practically few actually do that if you are using XY or dual mics most of the time folks will just orient the mic so one capsule is aimed at what you are recording. Convention is that it's the Left track but it's not a rule. With M/S you just use the M and toss the S. Part of this is because with most mics the adjustment is on the mic which is usually buried in wind protection and so a PITA to switch. If someone is using a stereo mic it is generally because of the convenience. Most stereo mics have smaller capsules that a small condenser mono mic has so most folks would rather record with a pair if that was easy. To that end a fair number of recordists I know have two capsules in a dual mount in a single zeppelin. Neumann makes an adapter that lets you seperate the capsule from the body by a small cable and Rycote has a zeppelin that is a little bigger than a nerf ball that holds both capsules. That set up is popular but fairly pricey. It sounds great and the combo makes the zep and mics very light. You can also rig two small condensers in a zep in a somewhat tight stereo set up, it's not as small or light but again it is convenient.
 
I think a mid-side mic with separate outputs (not internally matrixed) is a great all-arounder. In cases where I wish I had recorded stereo, Schoeps Mono Upmix plugin did a commendable job. It goes on sale every now and then for around 30-50 bucks.
 
Everyone is forgetting the plain and simple facts here. Stereo imaging and an accurate stereo field rely on two physical properties, time arrival and pressure. Outside there is a big problem - the wind! Remember the speed of sound is always quoted in still air.outside it is far from still, so if in your headphones something suddenly appears to lurch to one side, or vanishes totally in a gust, that’s a real problem. Football stadiums tend to be enclosed and you can do crowd noises and general atmosphere in stereo, but do it on an open field and it’s much, much worse.
 
Hi Paul,

I wonder whether you have sown a few potential seeds of confusion?

paulears said:
Everyone is forgetting the plain and simple facts here. Stereo imaging and an accurate stereo field rely on two physical properties, time arrival and pressure.
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Stereo imaging is dependent on time differences and level (not pressure) differences: obviously with coincident mics (e.g. XY) the directional differences are dependent of level differences only; with some set ups such as ORTF and NOS, it is a combination of both time differences and level differences; and with spaced omni mics it is time differences that give the directional component.

paulears said:
Outside there is a big problem - the wind! Remember the speed of sound is always quoted in still air.outside it is far from still, so if in your headphones something suddenly appears to lurch to one side, or vanishes totally in a gust, that’s a real problem. Football stadiums tend to be enclosed and you can do crowd noises and general atmosphere in stereo, but do it on an open field and it’s much, much worse.
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Really? I spend most of my time recording outdoors in stereo, and not in football stadia, and yet have not suffered this as a real problem: and I am often recording things with a very precise stereo image (including music). I'm not saying that it doesn't happen in strong gusts (where the effect just becomes subsumed - and a contributor to - the overall effect of a swirling gust, dominated by noise of the wind hitting objects), but to suggest it is a routine problem with recording outside is really overstating the case. Most outside recording (unless after wind effects) is not done in high wind anyway, for obvious reasons. So I'm interested to know more as to why you have found it 'much, much worse'? Perhaps you could post some examples of where this has proven a real problem for you, with details of the stereo pair used?

Cheers,

Roland
 
Pressure vs pressure gradient? Still pressure. Next time you are outside recording put a point source dead centre and watch the result on a stereo phase meter. Watch it wobble all over the place. First noticed 30 years ago when somebody had a lineup tone going through a guitar amp. The X/Y pair did very strage things. You'll be surprised.
 
paulears said:
Pressure vs pressure gradient? Still pressure. Next time you are outside recording put a point source dead centre and watch the result on a stereo phase meter. Watch it wobble all over the place. First noticed 30 years ago when somebody had a lineup tone going through a guitar amp. The X/Y pair did very strage things. You'll be surprised.
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I'm sure I could measure it if I felt the need. My point is that a shifting stereo image is not a significant issue when recording outside in normal conditions (and where windy, it is part of the effect: as with ones ears), and that you make the 'big problem' sound so intractable outside football stadia: there are many of us recording routinely in stereo outside and producing unproblematic stereo images. As I said, it would be helpful - and instructive - to post some examples of where you feel the shifting stereo image proved so problematic.

Cheers,

Roland
 
Clearly, what you and I think acceptable are different. It's not a problem for you, so that's fine. I don't record stereo outside now, or for the past ten years maybe? I don't like the result, so I don't do it. If I can find some old material I'll happily put it up, just the time required to do the search. I'll have a go if I fall over some old stuff.
 
I struck lucky with an example quite quickly.

Here are two files. The stereo one is recorded with a zoom, with the fixed X/Y mics, with the foam windshield covered in a fur fabric extra windshield. The mono one is a 416 in a zepplin with hairy Rycote. Recorded on a very blustery day, not far from here on a beach facing the North Sea. If you listen you can hear the sound of the waves on the shingle beach, and as the wind is gusting the image shifts quite horribly from right to left - try it on headphones and it's quite disconcerting and you almost hear two distinct separate channels, not the solid image you would normally get on a wind free day. The mono recording is much less exciting and too dull, but the stereo recording just sounds unreal. The zoom stereo field is normally very stable.

You'll have to decide for yourselves if you could live with the stereo field from X\Y at a distance. I have trouble with it's realism and accuracy.

https://www.eastanglianradio.com/monobeach.mp3
https://www.eastanglianradio.com/stereobeach.mp3
 
paulears said:
Clearly, what you and I think acceptable are different. It's not a problem for you, so that's fine. I don't record stereo outside now, or for the past ten years maybe? I don't like the result, so I don't do it. If I can find some old material I'll happily put it up, just the time required to do the search. I'll have a go if I fall over some old stuff.
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Hi Paul,

If you can find some old recordings that illustrate such problems with wind blowing the stereo image all over the place that would be great: I'm genuinely interested. Meanwhile, the 'what you and I think acceptable are different' interpretation is far from 'clear': as I said, I spend a lot of time recording outside in stereo (as do others with even more refined sensibilities and far greater credentials!), and have been doing so since my Nagra days in the mid-80s (incidentally with much of it nearly on your doorstep!). I suspect our different experiences lie in the different wind conditions (I can't deny that I seek out the most windless days: indeed, so much so that I often use very low self-noise LDC mics on location), the subjects that are being recorded, and the different techniques. Where we certainly differ, is that I would encourage others to record in stereo outside - where relevant to the task in hand, of course.

All the very best,

Roland

Edit: I was typing this while you posted your most recent post Paul. Thanks for the samples. As I suspected, nothing to do with our different levels of what is acceptable. That stereo recording is horrible to my ears too! On the one hand, this confirms my thoughts about different conditions (i.e. I mostly record out of medium let alone string wind; on the other, I have heard plenty of windy recordings that don't sound like this.
 
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This is intriguing - I tried it on speakers and sounded quite normal, so I tried on my IEMs and something odd happened. The footsteps went BEHIND me, not in front. Anyone else hear this? Really spooky - no idea why that happens - the waves were stereo and in front.
 
paulears said:
This is intriguing - I tried it on speakers and sounded quite normal, so I tried on my IEMs and something odd happened. The footsteps went BEHIND me, not in front. Anyone else hear this? Really spooky - no idea why that happens - the waves were stereo and in front.
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They went directly through my brain.
 
Most surround and image manipulation is based on M/S phase techniques. These can also be applied to stereo and some well know systems such as Q sound etc have done this quite well.

I used to have a fab console for post called and AMS Neve DFC and it was an automateable A/B wide control that could change the S content on any stereo signal and it was always good fun playing with the stereo imaging to expand or narrow things.

With sources such as footsteps etc it can be quite interesting if you record them with an M/S mic to A/B and if they move from the M to the S domain you can get the kind of spatial movement that you have described. It's all done with phase manipulation and sometimes that can be used to great effect.
 
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